[clang][ubsan] Split Implicit Integer Truncation Sanitizer into unsigned and signed checks

[lebedev.ri]

Summary

As per IRC disscussion, it seems we really want to have more fine-grained -fsanitize=implicit-integer-truncation:

• A check when both of the types are unsigned.
• Another check for the other cases (either one of the types is signed, or both of the types is signed).

This is clang part.
Compiler-rt part is D50902.

[vsk]

test/CodeGen/catch-implicit-integer-truncations-basics-negatives.c

24

It looks like 'CHECK: }' is meant to check that the end of the function is reached without any diagnostic handlers being emitted. If so, you'll need something stricter to actually check that.

Considering removing all of the 'CHECK: }' lines and adding -implicit-check-not=__ubsan_handle_implicit as a FileCheck option.

test/CodeGen/catch-implicit-signed-integer-truncations-basics-negatives.c

18

Ditto, I think this applies to the rest of the tests.

[lebedev.ri]

test/CodeGen/catch-implicit-integer-truncations-basics-negatives.c

24

I already specify -implicit-check-not="call void @__ubsan_handle_implicit_conversion".
As for the // CHECK: }, i know it doesn't do anything by itself, so i could indeed drop that indeed.

[lebedev.ri]

Rebased, addressed @vsk review note, should be NFC.

@vsk thank you for taking a look!

<vedantk> LebedevRI: It looks like it's in good shape. I wasn't around for the discussion re: splitting up the (un)signed cases, so it'd be good to have someone involved with that sign off

@rsmith ?

[lebedev.ri]

ping.

[lebedev.ri]

Ping.

[lebedev.ri]

Ping once again :)

[lebedev.ri]

@rsmith - ping.
This one should be rather uncontroversial i think? Is this moving in the direction you suggested? :)

[vitalybuka]

lib/CodeGen/CGExprScalar.cpp

305

why do you need to keep it?

[lebedev.ri]

@vsk thanks for taking a look!

lib/CodeGen/CGExprScalar.cpp

305

*Here* - for consistency with the compiler-rt part.

There - what about mismatch in the used clang version
(which still only produced the (ImplicitConversionCheckKind)0), and compiler-rt version
(which has (ImplicitConversionCheckKind)1 and (ImplicitConversionCheckKind)2)?
Is it 100.00% guaranteed not to happen? I'm not so sure.

[lebedev.ri]

In D50901#1238795, @lebedev.ri wrote:

@vsk thanks for taking a look!

/me can't read :)
That was supposed to be @vitalybuka, of course (:

[vitalybuka]

lib/CodeGen/CGExprScalar.cpp

305

I don't think we try support mismatched versions of clang and compiler-rt

[lebedev.ri]

• Split off the NFC preparatory changes.
• Rebased.

[filcab]

lib/CodeGen/CGExprScalar.cpp

305

We don't make a big effort in open source. But we try to at least make it work (check previous work on type_mismatch handler, before versions were introduced), or error "loudly" when linking (versioned checks).

I think having keeping the older check number free is a good thing and allows us to have binary compatibility with older objects (and keep supporting old object files (we *did* release llvm 7.0 with the old-type check)).

If we hadn't had a release in between, I'd be all for reusing.

[lebedev.ri]

• Rebased

[lebedev.ri]

As requested in https://reviews.llvm.org/D50902#1250110, actually document that ICCK_IntegerTruncation was only emitted by clang 7.

[lebedev.ri]

Ping! It seemed we were so close here :)

[filcab]

Sorry about that. I’m away today but I don’t think you’ve answered my
questions about “why not support standalone UBSan in tests”. Sorry if I
missed the answers if you did. Will review the latest tomorrow.

Thank you,
Filipe

[lebedev.ri]

In D50901#1257651, @filcab wrote:

Sorry about that. I’m away today but I don’t think you’ve answered my
questions about “why not support standalone UBSan in tests”. Sorry if I
missed the answers if you did.

I did answer that question twice now :)

https://reviews.llvm.org/D50902#inline-463926

Can't we simply not test on the SUMMARY line (test on the error line) and allow standalone too? I don't see what we gain by restricting the test.

That summary line is the very essence of what we are checking in this test.
We can only do that in non-standalone builds, because standalone builds only print generic undefined-behavior error name, while ubsan is coupled with some other sanitizer, an actual error name is printed.
We have discussed this with you in https://reviews.llvm.org/D48959#inline-429528

Will review the latest tomorrow.

Thank you,
Filipe

[rsmith]

This looks good to me. Sounds like @filcab is intending on doing another round of review too, so it'd make sense to double-check there before committing.

docs/UndefinedBehaviorSanitizer.rst

101

this sanitizer -> these sanitizers

[filcab]

LGTM on the clang side too.

Thank you,
Filipe

[lebedev.ri]

In D50901#1261203, @rsmith wrote:

This looks good to me. Sounds like @filcab is intending on doing another round of review too, so it'd make sense to double-check there before committing.

In D50901#1261312, @filcab wrote:

LGTM on the clang side too.

Thank you,
Filipe

YAY \0/
Thank you for the review!

docs/UndefinedBehaviorSanitizer.rst

Available checks are:
   -  ``-fsanitize=float-cast-overflow``: Conversion to, from, or
      between floating-point types which would overflow the
      destination.
   -  ``-fsanitize=float-divide-by-zero``: Floating point division by
      zero.
   -  ``-fsanitize=function``: Indirect call of a function through a
      function pointer of the wrong type (Darwin/Linux, C++ and x86/x86_64
      only).
-  -  ``-fsanitize=implicit-integer-truncation``: Implicit conversion from
+  -  ``-fsanitize=implicit-unsigned-integer-truncation``,
+     ``-fsanitize=implicit-signed-integer-truncation``: Implicit conversion from
      integer of larger bit width to smaller bit width, if that results in data
      loss. That is, if the demoted value, after casting back to the original
      width, is not equal to the original value before the downcast.
+     The ``-fsanitize=implicit-unsigned-integer-truncation`` handles conversions
+     between two ``unsigned`` types, while
+     ``-fsanitize=implicit-signed-integer-truncation`` handles the rest of the
+     conversions - when either one, or both of the types are signed.
      Issues caught by this sanitizer are not undefined behavior,
      but are often unintentional.
   -  ``-fsanitize=integer-divide-by-zero``: Integer division by zero.
   -  ``-fsanitize=nonnull-attribute``: Passing null pointer as a function
      parameter which is declared to never be null.
   -  ``-fsanitize=null``: Use of a null pointer or creation of a null
      reference.
   -  ``-fsanitize=nullability-arg``: Passing null as a function parameter
      which is annotated with ``_Nonnull``.
-  ``-fsanitize=undefined``: All of the checks listed above other than
      ``unsigned-integer-overflow``, ``implicit-conversion`` and the
      ``nullability-*`` group of checks.
   -  ``-fsanitize=undefined-trap``: Deprecated alias of
      ``-fsanitize=undefined``.
   -  ``-fsanitize=integer``: Checks for undefined or suspicious integer
      behavior (e.g. unsigned integer overflow).
      Enables ``signed-integer-overflow``, ``unsigned-integer-overflow``,
      ``shift``, ``integer-divide-by-zero``, and ``implicit-integer-truncation``.
+  -  ``fsanitize=implicit-integer-truncation``: Checks for implicit integral
+     conversions that result in data loss.
+     Enables ``implicit-unsigned-integer-truncation`` and
+     ``implicit-signed-integer-truncation``.
   -  ``-fsanitize=implicit-conversion``: Checks for suspicious behaviours of
      implicit conversions.
      Currently, only ``-fsanitize=implicit-integer-truncation`` is implemented.
   -  ``-fsanitize=nullability``: Enables ``nullability-arg``,
      ``nullability-assign``, and ``nullability-return``. While violating
      nullability does not have undefined behavior, it is often unintentional,
      so UBSan offers to catch it.
 

include/clang/Basic/Sanitizers.def

SANITIZER_GROUP("undefined", Undefined,
                     PointerOverflow | Return | ReturnsNonnullAttribute | Shift |
                     SignedIntegerOverflow | Unreachable | VLABound | Function |
                     Vptr)
 
 // -fsanitize=undefined-trap is an alias for -fsanitize=undefined.
 SANITIZER_GROUP("undefined-trap", UndefinedTrap, Undefined)
 
 // ImplicitConversionSanitizer
-SANITIZER("implicit-integer-truncation", ImplicitIntegerTruncation)
+SANITIZER("implicit-unsigned-integer-truncation",
+          ImplicitUnsignedIntegerTruncation)
+SANITIZER("implicit-signed-integer-truncation", ImplicitSignedIntegerTruncation)
+SANITIZER_GROUP("implicit-integer-truncation", ImplicitIntegerTruncation,
+                ImplicitUnsignedIntegerTruncation |
+                    ImplicitSignedIntegerTruncation)
+
 SANITIZER_GROUP("implicit-conversion", ImplicitConversion,
                 ImplicitIntegerTruncation)
 
 SANITIZER_GROUP("integer", Integer,
                 ImplicitIntegerTruncation | IntegerDivideByZero | Shift |
                     SignedIntegerOverflow | UnsignedIntegerOverflow)
 
 SANITIZER("local-bounds", LocalBounds)

lib/CodeGen/CGExprScalar.cpp

public:
   /// overflow.
   void EmitFloatConversionCheck(Value *OrigSrc, QualType OrigSrcType,
                                 Value *Src, QualType SrcType, QualType DstType,
                                 llvm::Type *DstTy, SourceLocation Loc);
 
   /// Known implicit conversion check kinds.
   /// Keep in sync with the enum of the same name in ubsan_handlers.h
   enum ImplicitConversionCheckKind : unsigned char {
-    ICCK_IntegerTruncation = 0,
+    ICCK_IntegerTruncation = 0, // Legacy, no longer used.
+    ICCK_UnsignedIntegerTruncation = 1,
+    ICCK_SignedIntegerTruncation = 2,
   };
 
   /// Emit a check that an [implicit] truncation of an integer  does not
   /// discard any bits. It is not UB, so we use the value after truncation.
   void EmitIntegerTruncationCheck(Value *Src, QualType SrcType, Value *Dst,
                                   QualType DstType, SourceLocation Loc);
 
   /// Emit a conversion from the specified type to the specified destination
llvm::Constant *StaticArgs[] = {CGF.EmitCheckSourceLocation(Loc),
                                   CGF.EmitCheckTypeDescriptor(DstType)};
   CGF.EmitCheck(std::make_pair(Check, SanitizerKind::FloatCastOverflow),
                 SanitizerHandler::FloatCastOverflow, StaticArgs, OrigSrc);
 }
 
 void ScalarExprEmitter::EmitIntegerTruncationCheck(Value *Src, QualType SrcType,
                                                    Value *Dst, QualType DstType,
                                                    SourceLocation Loc) {
-  if (!CGF.SanOpts.has(SanitizerKind::ImplicitIntegerTruncation))
+  if (!CGF.SanOpts.hasOneOf(SanitizerKind::ImplicitIntegerTruncation))
     return;
 
   llvm::Type *SrcTy = Src->getType();
   llvm::Type *DstTy = Dst->getType();
 
   // We only care about int->int conversions here.
   // We ignore conversions to/from pointer and/or bool.
   if (!(SrcType->isIntegerType() && DstType->isIntegerType()))
     return;
 
   assert(isa<llvm::IntegerType>(SrcTy) && isa<llvm::IntegerType>(DstTy) &&
          "clang integer type lowered to non-integer llvm type");
 
   unsigned SrcBits = SrcTy->getScalarSizeInBits();
   unsigned DstBits = DstTy->getScalarSizeInBits();
   // This must be truncation. Else we do not care.
   if (SrcBits <= DstBits)
     return;
 
   assert(!DstType->isBooleanType() && "we should not get here with booleans.");
 
+  bool SrcSigned = SrcType->isSignedIntegerOrEnumerationType();
+  bool DstSigned = DstType->isSignedIntegerOrEnumerationType();
+
+  // If both (src and dst) types are unsigned, then it's an unsigned truncation.
+  // Else, it is a signed truncation.
+  ImplicitConversionCheckKind Kind;
+  SanitizerMask Mask;
+  if (!SrcSigned && !DstSigned) {
+    Kind = ICCK_UnsignedIntegerTruncation;
+    Mask = SanitizerKind::ImplicitUnsignedIntegerTruncation;
+  } else {
+    Kind = ICCK_SignedIntegerTruncation;
+    Mask = SanitizerKind::ImplicitSignedIntegerTruncation;
+  }
+
+  // Do we care about this type of truncation?
+  if (!CGF.SanOpts.has(Mask))
+    return;
+
   CodeGenFunction::SanitizerScope SanScope(&CGF);
 
   llvm::Value *Check = nullptr;
 
   // 1. Extend the truncated value back to the same width as the Src.
-  bool InputSigned = DstType->isSignedIntegerOrEnumerationType();
-  Check = Builder.CreateIntCast(Dst, SrcTy, InputSigned, "anyext");
+  Check = Builder.CreateIntCast(Dst, SrcTy, DstSigned, "anyext");
   // 2. Equality-compare with the original source value
   Check = Builder.CreateICmpEQ(Check, Src, "truncheck");
   // If the comparison result is 'i1 false', then the truncation was lossy.
 
   llvm::Constant *StaticArgs[] = {
       CGF.EmitCheckSourceLocation(Loc), CGF.EmitCheckTypeDescriptor(SrcType),
       CGF.EmitCheckTypeDescriptor(DstType),
-      llvm::ConstantInt::get(Builder.getInt8Ty(), ICCK_IntegerTruncation)};
-  CGF.EmitCheck(std::make_pair(Check, SanitizerKind::ImplicitIntegerTruncation),
+      llvm::ConstantInt::get(Builder.getInt8Ty(), Kind)};
+  CGF.EmitCheck(std::make_pair(Check, Mask),
                 SanitizerHandler::ImplicitConversion, StaticArgs, {Src, Dst});
 }
 
 /// Emit a conversion from the specified type to the specified destination type,
 /// both of which are LLVM scalar types.
 Value *ScalarExprEmitter::EmitScalarConversion(Value *Src, QualType SrcType,
                                                QualType DstType,
                                                SourceLocation Loc,
case CK_VectorSplat: {
     Value *Elt = Visit(const_cast<Expr*>(E));
     // Splat the element across to all elements
     unsigned NumElements = DstTy->getVectorNumElements();
     return Builder.CreateVectorSplat(NumElements, Elt, "splat");
   }
 
   case CK_IntegralCast: {
     ScalarConversionOpts Opts;
-    if (CGF.SanOpts.has(SanitizerKind::ImplicitIntegerTruncation)) {
+    if (CGF.SanOpts.hasOneOf(SanitizerKind::ImplicitIntegerTruncation)) {
       if (auto *ICE = dyn_cast<ImplicitCastExpr>(CE))
         Opts.EmitImplicitIntegerTruncationChecks = !ICE->isPartOfExplicitCast();
     }
     return EmitScalarConversion(Visit(E), E->getType(), DestTy,
                                 CE->getExprLoc(), Opts);
   }
   case CK_IntegralToFloating:
   case CK_FloatingToIntegral:

test/CodeGen/catch-implicit-integer-conversions-basics.c

-// RUN: %clang_cc1 -fsanitize=implicit-integer-truncation -fsanitize-recover=implicit-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK
+// RUN: %clang_cc1 -fsanitize=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -fsanitize-recover=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK
 
 // Test plan:
 //  * Two types - int and char
 //  * Two signs - signed and unsigned
 //  * Square that - we have input and output types.
 // Thus, there are total of (2*2)^2 == 16 tests.
 // These are all the possible variations/combinations of casts.
 // However, not all of them should result in the check.
 // So here, we *only* check which should and which should not result in checks.
 
-// CHECK-DAG: @[[LINE_500_TRUNCATION:.*]] = {{.*}}, i32 500, i32 10 }, {{.*}}, {{.*}}, i8 0 }
-// CHECK-DAG: @[[LINE_1100_TRUNCATION:.*]] = {{.*}}, i32 1100, i32 10 }, {{.*}}, {{.*}}, i8 0 }
-// CHECK-DAG: @[[LINE_1500_TRUNCATION:.*]] = {{.*}}, i32 1500, i32 10 }, {{.*}}, {{.*}}, i8 0 }
-// CHECK-DAG: @[[LINE_1600_TRUNCATION:.*]] = {{.*}}, i32 1600, i32 10 }, {{.*}}, {{.*}}, i8 0 }
+// CHECK-DAG: @[[LINE_500_UNSIGNED_TRUNCATION:.*]] = {{.*}}, i32 500, i32 10 }, {{.*}}, {{.*}}, i8 1 }
+// CHECK-DAG: @[[LINE_1100_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 1100, i32 10 }, {{.*}}, {{.*}}, i8 2 }
+// CHECK-DAG: @[[LINE_1500_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 1500, i32 10 }, {{.*}}, {{.*}}, i8 2 }
+// CHECK-DAG: @[[LINE_1600_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 1600, i32 10 }, {{.*}}, {{.*}}, i8 2 }
 
 // CHECK-LABEL: @convert_unsigned_int_to_unsigned_int
 unsigned int convert_unsigned_int_to_unsigned_int(unsigned int x) {
-  // CHECK: }
 #line 100
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_char_to_unsigned_char
 unsigned char convert_unsigned_char_to_unsigned_char(unsigned char x) {
-  // CHECK: }
 #line 200
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_int_to_signed_int
 signed int convert_signed_int_to_signed_int(signed int x) {
-  // CHECK: }
 #line 300
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_char_to_signed_char
 signed char convert_signed_char_to_signed_char(signed char x) {
-  // CHECK: }
 #line 400
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_int_to_unsigned_char
 unsigned char convert_unsigned_int_to_unsigned_char(unsigned int x) {
-  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_500_TRUNCATION]] to i8*)
-  // CHECK: }
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_500_UNSIGNED_TRUNCATION]] to i8*)
 #line 500
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_char_to_unsigned_int
 unsigned int convert_unsigned_char_to_unsigned_int(unsigned char x) {
-  // CHECK: }
 #line 600
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_char_to_signed_int
 signed int convert_unsigned_char_to_signed_int(unsigned char x) {
-  // CHECK: }
 #line 700
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_char_to_signed_int
 signed int convert_signed_char_to_signed_int(signed char x) {
-  // CHECK: }
 #line 800
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_int_to_signed_int
 signed int convert_unsigned_int_to_signed_int(unsigned int x) {
-  // CHECK: }
 #line 900
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_int_to_unsigned_int
 unsigned int convert_signed_int_to_unsigned_int(signed int x) {
-  // CHECK: }
 #line 1000
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_int_to_unsigned_char
 unsigned char convert_signed_int_to_unsigned_char(signed int x) {
-  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1100_TRUNCATION]] to i8*)
-  // CHECK: }
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1100_SIGNED_TRUNCATION]] to i8*)
 #line 1100
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_char_to_unsigned_char
 unsigned char convert_signed_char_to_unsigned_char(signed char x) {
-  // CHECK: }
 #line 1200
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_char_to_signed_char
 signed char convert_unsigned_char_to_signed_char(unsigned char x) {
-  // CHECK: }
 #line 1300
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_char_to_unsigned_int
 unsigned int convert_signed_char_to_unsigned_int(signed char x) {
-  // CHECK: }
 #line 1400
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_int_to_signed_char
 signed char convert_unsigned_int_to_signed_char(unsigned int x) {
-  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1500_TRUNCATION]] to i8*)
-  // CHECK: }
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1500_SIGNED_TRUNCATION]] to i8*)
 #line 1500
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_int_to_signed_char
 signed char convert_signed_int_to_signed_char(signed int x) {
-  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1600_TRUNCATION]] to i8*)
-  // CHECK: }
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1600_SIGNED_TRUNCATION]] to i8*)
 #line 1600
   return x;
 }

test/CodeGen/catch-implicit-integer-truncations-basics-negatives.c

+// RUN: %clang_cc1 -fsanitize=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -fsanitize-recover=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK
+
+// CHECK-DAG: @[[LINE_100_UNSIGNED_TRUNCATION:.*]] = {{.*}}, i32 100, i32 10 }, {{.*}}, {{.*}}, i8 1 }
+// CHECK-DAG: @[[LINE_200_UNSIGNED_TRUNCATION:.*]] = {{.*}}, i32 200, i32 10 }, {{.*}}, {{.*}}, i8 1 }
+// CHECK-DAG: @[[LINE_300_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 300, i32 10 }, {{.*}}, {{.*}}, i8 2 }
+// CHECK-DAG: @[[LINE_400_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 400, i32 10 }, {{.*}}, {{.*}}, i8 2 }
+
+//----------------------------------------------------------------------------//
+// Unsigned case.
+//----------------------------------------------------------------------------//
+
+// CHECK-LABEL: @blacklist_0_convert_unsigned_int_to_unsigned_char
+__attribute__((no_sanitize("undefined"))) unsigned char blacklist_0_convert_unsigned_int_to_unsigned_char(unsigned int x) {
+  // We are not in "undefined" group, so that doesn't work.
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_100_UNSIGNED_TRUNCATION]] to i8*)
+#line 100
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_1_convert_unsigned_int_to_unsigned_char
+__attribute__((no_sanitize("integer"))) unsigned char blacklist_1_convert_unsigned_int_to_unsigned_char(unsigned int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_2_convert_unsigned_int_to_unsigned_char
+__attribute__((no_sanitize("implicit-conversion"))) unsigned char blacklist_2_convert_unsigned_int_to_unsigned_char(unsigned int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_3_convert_unsigned_int_to_unsigned_char
+__attribute__((no_sanitize("implicit-integer-truncation"))) unsigned char blacklist_3_convert_unsigned_int_to_unsigned_char(unsigned int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_4_convert_unsigned_int_to_unsigned_char
+__attribute__((no_sanitize("implicit-unsigned-integer-truncation"))) unsigned char blacklist_4_convert_unsigned_int_to_unsigned_char(unsigned int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_5_convert_unsigned_int_to_unsigned_char
+__attribute__((no_sanitize("implicit-signed-integer-truncation"))) unsigned char blacklist_5_convert_unsigned_int_to_unsigned_char(unsigned int x) {
+  // This is an unsigned truncation, not signed-one.
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_200_UNSIGNED_TRUNCATION]] to i8*)
+#line 200
+  return x;
+}
+
+//----------------------------------------------------------------------------//
+// Signed case.
+//----------------------------------------------------------------------------//
+
+// CHECK-LABEL: @blacklist_0_convert_signed_int_to_signed_char
+__attribute__((no_sanitize("undefined"))) signed char blacklist_0_convert_signed_int_to_signed_char(signed int x) {
+  // We are not in "undefined" group, so that doesn't work.
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_300_SIGNED_TRUNCATION]] to i8*)
+#line 300
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_1_convert_signed_int_to_signed_char
+__attribute__((no_sanitize("integer"))) signed char blacklist_1_convert_signed_int_to_signed_char(signed int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_2_convert_signed_int_to_signed_char
+__attribute__((no_sanitize("implicit-conversion"))) signed char blacklist_2_convert_signed_int_to_signed_char(signed int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_3_convert_signed_int_to_signed_char
+__attribute__((no_sanitize("implicit-integer-truncation"))) signed char blacklist_3_convert_signed_int_to_signed_char(signed int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_4_convert_signed_int_to_signed_char
+__attribute__((no_sanitize("implicit-signed-integer-truncation"))) signed char blacklist_4_convert_signed_int_to_signed_char(signed int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_5_convert_signed_int_to_signed_char
+__attribute__((no_sanitize("implicit-unsigned-integer-truncation"))) signed char blacklist_5_convert_signed_int_to_signed_char(signed int x) {
+  // This is an signed truncation, not unsigned-one.
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_400_SIGNED_TRUNCATION]] to i8*)
+#line 400
+  return x;
+}

test/CodeGen/catch-implicit-integer-truncations-basics.c

-// RUN: %clang_cc1 -fsanitize=implicit-integer-truncation -fsanitize-recover=implicit-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK
+// RUN: %clang_cc1 -fsanitize=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -fsanitize-recover=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK
 
 // Test plan:
 //  * Two types - int and char
 //  * Two signs - signed and unsigned
 //  * Square that - we have input and output types.
 // Thus, there are total of (2*2)^2 == 16 tests.
 // These are all the possible variations/combinations of casts.
 // However, not all of them should result in the check.
 // So here, we *only* check which should and which should not result in checks.
 
-// CHECK-DAG: @[[LINE_500_TRUNCATION:.*]] = {{.*}}, i32 500, i32 10 }, {{.*}}, {{.*}}, i8 0 }
-// CHECK-DAG: @[[LINE_1100_TRUNCATION:.*]] = {{.*}}, i32 1100, i32 10 }, {{.*}}, {{.*}}, i8 0 }
-// CHECK-DAG: @[[LINE_1500_TRUNCATION:.*]] = {{.*}}, i32 1500, i32 10 }, {{.*}}, {{.*}}, i8 0 }
-// CHECK-DAG: @[[LINE_1600_TRUNCATION:.*]] = {{.*}}, i32 1600, i32 10 }, {{.*}}, {{.*}}, i8 0 }
+// CHECK-DAG: @[[LINE_500_UNSIGNED_TRUNCATION:.*]] = {{.*}}, i32 500, i32 10 }, {{.*}}, {{.*}}, i8 1 }
+// CHECK-DAG: @[[LINE_1100_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 1100, i32 10 }, {{.*}}, {{.*}}, i8 2 }
+// CHECK-DAG: @[[LINE_1500_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 1500, i32 10 }, {{.*}}, {{.*}}, i8 2 }
+// CHECK-DAG: @[[LINE_1600_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 1600, i32 10 }, {{.*}}, {{.*}}, i8 2 }
 
 // CHECK-LABEL: @convert_unsigned_int_to_unsigned_int
 unsigned int convert_unsigned_int_to_unsigned_int(unsigned int x) {
-  // CHECK: }
 #line 100
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_char_to_unsigned_char
 unsigned char convert_unsigned_char_to_unsigned_char(unsigned char x) {
-  // CHECK: }
 #line 200
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_int_to_signed_int
 signed int convert_signed_int_to_signed_int(signed int x) {
-  // CHECK: }
 #line 300
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_char_to_signed_char
 signed char convert_signed_char_to_signed_char(signed char x) {
-  // CHECK: }
 #line 400
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_int_to_unsigned_char
 unsigned char convert_unsigned_int_to_unsigned_char(unsigned int x) {
-  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_500_TRUNCATION]] to i8*)
-  // CHECK: }
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_500_UNSIGNED_TRUNCATION]] to i8*)
 #line 500
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_char_to_unsigned_int
 unsigned int convert_unsigned_char_to_unsigned_int(unsigned char x) {
-  // CHECK: }
 #line 600
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_char_to_signed_int
 signed int convert_unsigned_char_to_signed_int(unsigned char x) {
-  // CHECK: }
 #line 700
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_char_to_signed_int
 signed int convert_signed_char_to_signed_int(signed char x) {
-  // CHECK: }
 #line 800
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_int_to_signed_int
 signed int convert_unsigned_int_to_signed_int(unsigned int x) {
-  // CHECK: }
 #line 900
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_int_to_unsigned_int
 unsigned int convert_signed_int_to_unsigned_int(signed int x) {
-  // CHECK: }
 #line 1000
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_int_to_unsigned_char
 unsigned char convert_signed_int_to_unsigned_char(signed int x) {
-  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1100_TRUNCATION]] to i8*)
-  // CHECK: }
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1100_SIGNED_TRUNCATION]] to i8*)
 #line 1100
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_char_to_unsigned_char
 unsigned char convert_signed_char_to_unsigned_char(signed char x) {
-  // CHECK: }
 #line 1200
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_char_to_signed_char
 signed char convert_unsigned_char_to_signed_char(unsigned char x) {
-  // CHECK: }
 #line 1300
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_char_to_unsigned_int
 unsigned int convert_signed_char_to_unsigned_int(signed char x) {
-  // CHECK: }
 #line 1400
   return x;
 }
 
 // CHECK-LABEL: @convert_unsigned_int_to_signed_char
 signed char convert_unsigned_int_to_signed_char(unsigned int x) {
-  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1500_TRUNCATION]] to i8*)
-  // CHECK: }
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1500_SIGNED_TRUNCATION]] to i8*)
 #line 1500
   return x;
 }
 
 // CHECK-LABEL: @convert_signed_int_to_signed_char
 signed char convert_signed_int_to_signed_char(signed int x) {
-  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1600_TRUNCATION]] to i8*)
-  // CHECK: }
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1600_SIGNED_TRUNCATION]] to i8*)
 #line 1600
   return x;
 }

test/CodeGen/catch-implicit-integer-truncations.c

 // RUN: %clang_cc1 -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefix=CHECK
-// RUN: %clang_cc1 -fsanitize=implicit-integer-truncation -fno-sanitize-recover=implicit-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK,CHECK-SANITIZE,CHECK-SANITIZE-ANYRECOVER,CHECK-SANITIZE-NORECOVER,CHECK-SANITIZE-UNREACHABLE
-// RUN: %clang_cc1 -fsanitize=implicit-integer-truncation -fsanitize-recover=implicit-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK,CHECK-SANITIZE,CHECK-SANITIZE-ANYRECOVER,CHECK-SANITIZE-RECOVER
-// RUN: %clang_cc1 -fsanitize=implicit-integer-truncation -fsanitize-trap=implicit-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK,CHECK-SANITIZE,CHECK-SANITIZE-TRAP,CHECK-SANITIZE-UNREACHABLE
+// RUN: %clang_cc1 -fsanitize=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -fno-sanitize-recover=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK,CHECK-SANITIZE,CHECK-SANITIZE-ANYRECOVER,CHECK-SANITIZE-NORECOVER,CHECK-SANITIZE-UNREACHABLE
+// RUN: %clang_cc1 -fsanitize=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -fsanitize-recover=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK,CHECK-SANITIZE,CHECK-SANITIZE-ANYRECOVER,CHECK-SANITIZE-RECOVER
+// RUN: %clang_cc1 -fsanitize=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -fsanitize-trap=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK,CHECK-SANITIZE,CHECK-SANITIZE-TRAP,CHECK-SANITIZE-UNREACHABLE
 
 // CHECK-SANITIZE-ANYRECOVER: @[[UNSIGNED_INT:.*]] = {{.*}} c"'unsigned int'\00" }
 // CHECK-SANITIZE-ANYRECOVER: @[[UNSIGNED_CHAR:.*]] = {{.*}} c"'unsigned char'\00" }
 
-// CHECK-SANITIZE-ANYRECOVER: @[[LINE_100:.*]] = {{.*}}, i32 100, i32 10 }, {{.*}}* @[[UNSIGNED_INT]], {{.*}}* @[[UNSIGNED_CHAR]], i8 0 }
+// CHECK-SANITIZE-ANYRECOVER: @[[LINE_100_UNSIGNED_TRUNCATION:.*]] = {{.*}}, i32 100, i32 10 }, {{.*}}* @[[UNSIGNED_INT]], {{.*}}* @[[UNSIGNED_CHAR]], i8 1 }
 // CHECK-SANITIZE-ANYRECOVER: @[[SIGNED_INT:.*]] = {{.*}} c"'int'\00" }
-// CHECK-SANITIZE-ANYRECOVER: @[[LINE_200:.*]] = {{.*}}, i32 200, i32 10 }, {{.*}}* @[[SIGNED_INT]], {{.*}}* @[[UNSIGNED_CHAR]], i8 0 }
+// CHECK-SANITIZE-ANYRECOVER: @[[LINE_200_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 200, i32 10 }, {{.*}}* @[[SIGNED_INT]], {{.*}}* @[[UNSIGNED_CHAR]], i8 2 }
 // CHECK-SANITIZE-ANYRECOVER: @[[SIGNED_CHAR:.*]] = {{.*}} c"'signed char'\00" }
-// CHECK-SANITIZE-ANYRECOVER: @[[LINE_300:.*]] = {{.*}}, i32 300, i32 10 }, {{.*}}* @[[UNSIGNED_INT]], {{.*}}* @[[SIGNED_CHAR]], i8 0 }
-// CHECK-SANITIZE-ANYRECOVER: @[[LINE_400:.*]] = {{.*}}, i32 400, i32 10 }, {{.*}}* @[[SIGNED_INT]], {{.*}}* @[[SIGNED_CHAR]], i8 0 }
+// CHECK-SANITIZE-ANYRECOVER: @[[LINE_300_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 300, i32 10 }, {{.*}}* @[[UNSIGNED_INT]], {{.*}}* @[[SIGNED_CHAR]], i8 2 }
+// CHECK-SANITIZE-ANYRECOVER: @[[LINE_400_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 400, i32 10 }, {{.*}}* @[[SIGNED_INT]], {{.*}}* @[[SIGNED_CHAR]], i8 2 }
 
 // CHECK-SANITIZE-ANYRECOVER: @[[UINT32:.*]] = {{.*}} c"'uint32_t' (aka 'unsigned int')\00" }
 // CHECK-SANITIZE-ANYRECOVER: @[[UINT8:.*]] = {{.*}} c"'uint8_t' (aka 'unsigned char')\00" }
-// CHECK-SANITIZE-ANYRECOVER: @[[LINE_500:.*]] = {{.*}}, i32 500, i32 10 }, {{.*}}* @[[UINT32]], {{.*}}* @[[UINT8]], i8 0 }
+// CHECK-SANITIZE-ANYRECOVER: @[[LINE_500_UNSIGNED_TRUNCATION:.*]] = {{.*}}, i32 500, i32 10 }, {{.*}}* @[[UINT32]], {{.*}}* @[[UINT8]], i8 1 }
 
 // ========================================================================== //
 // The expected true-positives. These are implicit conversions, and they truncate.
 // ========================================================================== //
 
 // CHECK-LABEL: @unsigned_int_to_unsigned_char
 unsigned char unsigned_int_to_unsigned_char(unsigned int src) {
   // CHECK: %[[DST:.*]] = trunc i32 %[[SRC:.*]] to i8
   // CHECK-SANITIZE-NEXT: %[[ANYEXT:.*]] = zext i8 %[[DST]] to i32, !nosanitize
   // CHECK-SANITIZE-NEXT: %[[TRUNCHECK:.*]] = icmp eq i32 %[[ANYEXT]], %[[SRC]], !nosanitize
   // CHECK-SANITIZE-NEXT: br i1 %[[TRUNCHECK]], label %[[CONT:.*]], label %[[HANDLER_IMPLICIT_CONVERSION:[^,]+]],{{.*}} !nosanitize
   // CHECK-SANITIZE: [[HANDLER_IMPLICIT_CONVERSION]]:
   // CHECK-SANITIZE-ANYRECOVER-NEXT: %[[EXTSRC:.*]] = zext i32 %[[SRC]] to i64, !nosanitize
   // CHECK-SANITIZE-ANYRECOVER-NEXT: %[[EXTDST:.*]] = zext i8 %[[DST]] to i64, !nosanitize
-  // CHECK-SANITIZE-NORECOVER-NEXT: call void @__ubsan_handle_implicit_conversion_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_100]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
-  // CHECK-SANITIZE-RECOVER-NEXT: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_100]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
+  // CHECK-SANITIZE-NORECOVER-NEXT: call void @__ubsan_handle_implicit_conversion_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_100_UNSIGNED_TRUNCATION]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
+  // CHECK-SANITIZE-RECOVER-NEXT: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_100_UNSIGNED_TRUNCATION]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
   // CHECK-SANITIZE-TRAP-NEXT: call void @llvm.trap(){{.*}}, !nosanitize
   // CHECK-SANITIZE-UNREACHABLE-NEXT: unreachable, !nosanitize
   // CHECK-SANITIZE: [[CONT]]:
   // CHECK-NEXT: ret i8 %[[DST]]
   // CHECK-NEXT: }
 #line 100
   return src;
 }
 
 // CHECK-LABEL: @signed_int_to_unsigned_char
 unsigned char signed_int_to_unsigned_char(signed int src) {
   // CHECK: %[[DST:.*]] = trunc i32 %[[SRC:.*]] to i8
   // CHECK-SANITIZE-NEXT: %[[ANYEXT:.*]] = zext i8 %[[DST]] to i32, !nosanitize
   // CHECK-SANITIZE-NEXT: %[[TRUNCHECK:.*]] = icmp eq i32 %[[ANYEXT]], %[[SRC]], !nosanitize
   // CHECK-SANITIZE-NEXT: br i1 %[[TRUNCHECK]], label %[[CONT:.*]], label %[[HANDLER_IMPLICIT_CONVERSION:[^,]+]],{{.*}} !nosanitize
   // CHECK-SANITIZE: [[HANDLER_IMPLICIT_CONVERSION]]:
   // CHECK-SANITIZE-ANYRECOVER-NEXT: %[[EXTSRC:.*]] = zext i32 %[[SRC]] to i64, !nosanitize
   // CHECK-SANITIZE-ANYRECOVER-NEXT: %[[EXTDST:.*]] = zext i8 %[[DST]] to i64, !nosanitize
-  // CHECK-SANITIZE-NORECOVER-NEXT: call void @__ubsan_handle_implicit_conversion_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_200]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
-  // CHECK-SANITIZE-RECOVER-NEXT: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_200]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
+  // CHECK-SANITIZE-NORECOVER-NEXT: call void @__ubsan_handle_implicit_conversion_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_200_SIGNED_TRUNCATION]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
+  // CHECK-SANITIZE-RECOVER-NEXT: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_200_SIGNED_TRUNCATION]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
   // CHECK-SANITIZE-TRAP-NEXT: call void @llvm.trap(){{.*}}, !nosanitize
   // CHECK-SANITIZE-UNREACHABLE-NEXT: unreachable, !nosanitize
   // CHECK-SANITIZE: [[CONT]]:
   // CHECK-NEXT: ret i8 %[[DST]]
   // CHECK-NEXT: }
 #line 200
   return src;
 }
 
 // CHECK-LABEL: @unsigned_int_to_signed_char
 signed char unsigned_int_to_signed_char(unsigned int src) {
   // CHECK: %[[DST:.*]] = trunc i32 %[[SRC:.*]] to i8
   // CHECK-SANITIZE-NEXT: %[[ANYEXT:.*]] = sext i8 %[[DST]] to i32, !nosanitize
   // CHECK-SANITIZE-NEXT: %[[TRUNCHECK:.*]] = icmp eq i32 %[[ANYEXT]], %[[SRC]], !nosanitize
   // CHECK-SANITIZE-NEXT: br i1 %[[TRUNCHECK]], label %[[CONT:.*]], label %[[HANDLER_IMPLICIT_CONVERSION:[^,]+]],{{.*}} !nosanitize
   // CHECK-SANITIZE: [[HANDLER_IMPLICIT_CONVERSION]]:
   // CHECK-SANITIZE-ANYRECOVER-NEXT: %[[EXTSRC:.*]] = zext i32 %[[SRC]] to i64, !nosanitize
   // CHECK-SANITIZE-ANYRECOVER-NEXT: %[[EXTDST:.*]] = zext i8 %[[DST]] to i64, !nosanitize
-  // CHECK-SANITIZE-NORECOVER-NEXT: call void @__ubsan_handle_implicit_conversion_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_300]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
-  // CHECK-SANITIZE-RECOVER-NEXT: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_300]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
+  // CHECK-SANITIZE-NORECOVER-NEXT: call void @__ubsan_handle_implicit_conversion_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_300_SIGNED_TRUNCATION]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
+  // CHECK-SANITIZE-RECOVER-NEXT: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_300_SIGNED_TRUNCATION]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
   // CHECK-SANITIZE-TRAP-NEXT: call void @llvm.trap(){{.*}}, !nosanitize
   // CHECK-SANITIZE-UNREACHABLE-NEXT: unreachable, !nosanitize
   // CHECK-SANITIZE: [[CONT]]:
   // CHECK-NEXT: ret i8 %[[DST]]
   // CHECK-NEXT: }
 #line 300
   return src;
 }
 
 // CHECK-LABEL: @signed_int_to_signed_char
 signed char signed_int_to_signed_char(signed int src) {
   // CHECK: %[[DST:.*]] = trunc i32 %[[SRC:.*]] to i8
   // CHECK-SANITIZE-NEXT: %[[ANYEXT:.*]] = sext i8 %[[DST]] to i32, !nosanitize
   // CHECK-SANITIZE-NEXT: %[[TRUNCHECK:.*]] = icmp eq i32 %[[ANYEXT]], %[[SRC]], !nosanitize
   // CHECK-SANITIZE-NEXT: br i1 %[[TRUNCHECK]], label %[[CONT:.*]], label %[[HANDLER_IMPLICIT_CONVERSION:[^,]+]],{{.*}} !nosanitize
   // CHECK-SANITIZE: [[HANDLER_IMPLICIT_CONVERSION]]:
   // CHECK-SANITIZE-ANYRECOVER-NEXT: %[[EXTSRC:.*]] = zext i32 %[[SRC]] to i64, !nosanitize
   // CHECK-SANITIZE-ANYRECOVER-NEXT: %[[EXTDST:.*]] = zext i8 %[[DST]] to i64, !nosanitize
-  // CHECK-SANITIZE-NORECOVER-NEXT: call void @__ubsan_handle_implicit_conversion_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_400]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
-  // CHECK-SANITIZE-RECOVER-NEXT: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_400]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
+  // CHECK-SANITIZE-NORECOVER-NEXT: call void @__ubsan_handle_implicit_conversion_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_400_SIGNED_TRUNCATION]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
+  // CHECK-SANITIZE-RECOVER-NEXT: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_400_SIGNED_TRUNCATION]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
   // CHECK-SANITIZE-TRAP-NEXT: call void @llvm.trap(){{.*}}, !nosanitize
   // CHECK-SANITIZE-UNREACHABLE-NEXT: unreachable, !nosanitize
   // CHECK-SANITIZE: [[CONT]]:
   // CHECK-NEXT: ret i8 %[[DST]]
   // CHECK-NEXT: }
 #line 400
   return src;
 }

 uint8_t uint32_to_uint8(uint32_t src) {
   // CHECK: %[[DST:.*]] = trunc i32 %[[SRC:.*]] to i8
   // CHECK-SANITIZE-NEXT: %[[ANYEXT:.*]] = zext i8 %[[DST]] to i32, !nosanitize
   // CHECK-SANITIZE-NEXT: %[[TRUNCHECK:.*]] = icmp eq i32 %[[ANYEXT]], %[[SRC]], !nosanitize
   // CHECK-SANITIZE-NEXT: br i1 %[[TRUNCHECK]], label %[[CONT:.*]], label %[[HANDLER_IMPLICIT_CONVERSION:[^,]+]],{{.*}} !nosanitize
   // CHECK-SANITIZE: [[HANDLER_IMPLICIT_CONVERSION]]:
   // CHECK-SANITIZE-ANYRECOVER-NEXT: %[[EXTSRC:.*]] = zext i32 %[[SRC]] to i64, !nosanitize
   // CHECK-SANITIZE-ANYRECOVER-NEXT: %[[EXTDST:.*]] = zext i8 %[[DST]] to i64, !nosanitize
-  // CHECK-SANITIZE-NORECOVER-NEXT: call void @__ubsan_handle_implicit_conversion_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_500]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
-  // CHECK-SANITIZE-RECOVER-NEXT: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_500]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
+  // CHECK-SANITIZE-NORECOVER-NEXT: call void @__ubsan_handle_implicit_conversion_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_500_UNSIGNED_TRUNCATION]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
+  // CHECK-SANITIZE-RECOVER-NEXT: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_500_UNSIGNED_TRUNCATION]] to i8*), i64 %[[EXTSRC]], i64 %[[EXTDST]]){{.*}}, !nosanitize
   // CHECK-SANITIZE-TRAP-NEXT: call void @llvm.trap(){{.*}}, !nosanitize
   // CHECK-SANITIZE-UNREACHABLE-NEXT: unreachable, !nosanitize
   // CHECK-SANITIZE: [[CONT]]:
   // CHECK-NEXT: ret i8 %[[DST]]
   // CHECK-NEXT: }
 #line 500
   return src;
 }
 
 // ========================================================================== //
 // Check that explicit conversion does not interfere with implicit conversion
 // ========================================================================== //
 // These contain one implicit truncating conversion, and one explicit truncating conversion.
 // We want to make sure that we still diagnose the implicit conversion.
 
 // Implicit truncation after explicit truncation.
 // CHECK-LABEL: @explicit_conversion_interference0
 unsigned char explicit_conversion_interference0(unsigned int c) {
   // CHECK-SANITIZE: %[[ANYEXT:.*]] = zext i8 %[[DST:.*]] to i16, !nosanitize
   // CHECK-SANITIZE: call
-  // CHECK: }
   return (unsigned short)c;
 }
 
 // Implicit truncation before explicit truncation.
 // CHECK-LABEL: @explicit_conversion_interference1
 unsigned char explicit_conversion_interference1(unsigned int c) {
   // CHECK-SANITIZE: %[[ANYEXT:.*]] = zext i16 %[[DST:.*]] to i32, !nosanitize
   // CHECK-SANITIZE: call
-  // CHECK: }
   unsigned short b;
   return (unsigned char)(b = c);
 }
 
 // ========================================================================== //
 // The expected true-negatives.
 // ========================================================================== //
 
 // Sanitization is explicitly disabled.
 // ========================================================================== //
 
 // CHECK-LABEL: @blacklist_0
 __attribute__((no_sanitize("undefined"))) unsigned char blacklist_0(unsigned int src) {
   // We are not in "undefined" group, so that doesn't work.
   // CHECK-SANITIZE: call
-  // CHECK: }
   return src;
 }
 
 // CHECK-LABEL: @blacklist_1
 __attribute__((no_sanitize("integer"))) unsigned char blacklist_1(unsigned int src) {
-  // CHECK: }
   return src;
 }
 
 // CHECK-LABEL: @blacklist_2
 __attribute__((no_sanitize("implicit-conversion"))) unsigned char blacklist_2(unsigned int src) {
-  // CHECK: }
   return src;
 }
 
 // CHECK-LABEL: @blacklist_3
 __attribute__((no_sanitize("implicit-integer-truncation"))) unsigned char blacklist_3(unsigned int src) {
-  // CHECK: }
   return src;
 }
 
 // Explicit truncating conversions.
 // ========================================================================== //
 
 // CHECK-LABEL: @explicit_unsigned_int_to_unsigned_char
 unsigned char explicit_unsigned_int_to_unsigned_char(unsigned int src) {
-  // CHECK: }
   return (unsigned char)src;
 }
 
 // CHECK-LABEL: @explicit_signed_int_to_unsigned_char
 unsigned char explicit_signed_int_to_unsigned_char(signed int src) {
-  // CHECK: }
   return (unsigned char)src;
 }
 
 // CHECK-LABEL: @explicit_unsigned_int_to_signed_char
 signed char explicit_unsigned_int_to_signed_char(unsigned int src) {
-  // CHECK: }
   return (signed char)src;
 }
 
 // CHECK-LABEL: @explicit_signed_int_to_signed_char
 signed char explicit_signed_int_to_signed_char(signed int src) {
-  // CHECK: }
   return (signed char)src;
 }
 
 // Explicit NOP conversions.
 // ========================================================================== //
 
 // CHECK-LABEL: @explicit_unsigned_int_to_unsigned_int
 unsigned int explicit_unsigned_int_to_unsigned_int(unsigned int src) {
-  // CHECK: }
   return (unsigned int)src;
 }
 
 // CHECK-LABEL: @explicit_signed_int_to_signed_int
 signed int explicit_signed_int_to_signed_int(signed int src) {
-  // CHECK: }
   return (signed int)src;
 }
 
 // CHECK-LABEL: @explicit_unsigned_char_to_signed_char
 unsigned char explicit_unsigned_char_to_signed_char(unsigned char src) {
-  // CHECK: }
   return (unsigned char)src;
 }
 
 // CHECK-LABEL: @explicit_signed_char_to_signed_char
 signed char explicit_signed_char_to_signed_char(signed char src) {
-  // CHECK: }
   return (signed char)src;
 }
 
 // upcasts.
 // ========================================================================== //
 
 // CHECK-LABEL: @unsigned_char_to_unsigned_int
 unsigned int unsigned_char_to_unsigned_int(unsigned char src) {
-  // CHECK: }
   return src;
 }
 
 // CHECK-LABEL: @signed_char_to_unsigned_int
 unsigned int signed_char_to_unsigned_int(signed char src) {
-  // CHECK: }
   return src;
 }
 
 // CHECK-LABEL: @unsigned_char_to_signed_int
 signed int unsigned_char_to_signed_int(unsigned char src) {
-  // CHECK: }
   return src;
 }
 
 // CHECK-LABEL: @signed_char_to_signed_int
 signed int signed_char_to_signed_int(signed char src) {
-  // CHECK: }
   return src;
 }
 
 // Explicit upcasts.
 // ========================================================================== //
 
 // CHECK-LABEL: @explicit_unsigned_char_to_unsigned_int
 unsigned int explicit_unsigned_char_to_unsigned_int(unsigned char src) {
-  // CHECK: }
   return (unsigned int)src;
 }
 
 // CHECK-LABEL: @explicit_signed_char_to_unsigned_int
 unsigned int explicit_signed_char_to_unsigned_int(signed char src) {
-  // CHECK: }
   return (unsigned int)src;
 }
 
 // CHECK-LABEL: @explicit_unsigned_char_to_signed_int
 signed int explicit_unsigned_char_to_signed_int(unsigned char src) {
-  // CHECK: }
   return (signed int)src;
 }
 
 // CHECK-LABEL: @explicit_signed_char_to_signed_int
 signed int explicit_signed_char_to_signed_int(signed char src) {
-  // CHECK: }
   return (signed int)src;
 }
 
 // conversions to to boolean type are not counted as truncation.
 // ========================================================================== //
 
 // CHECK-LABEL: @unsigned_int_to_bool
 _Bool unsigned_int_to_bool(unsigned int src) {
-  // CHECK: }
   return src;
 }
 
 // CHECK-LABEL: @signed_int_to_bool
 _Bool signed_int_to_bool(signed int src) {
-  // CHECK: }
   return src;
 }
 
 // CHECK-LABEL: @explicit_unsigned_int_to_bool
 _Bool explicit_unsigned_int_to_bool(unsigned int src) {
-  // CHECK: }
   return (_Bool)src;
 }
 
 // CHECK-LABEL: @explicit_signed_int_to_bool
 _Bool explicit_signed_int_to_bool(signed int src) {
-  // CHECK: }
   return (_Bool)src;
 }
 
 // Explicit truncating conversions from pointer to a much-smaller integer.
 // Can not have an implicit conversion from pointer to an integer.
 // Can not have an implicit conversion between two enums.
 // ========================================================================== //
 
 // CHECK-LABEL: @explicit_voidptr_to_unsigned_char
 unsigned char explicit_voidptr_to_unsigned_char(void *src) {
-  // CHECK: }
   return (unsigned char)src;
 }
 
 // CHECK-LABEL: @explicit_voidptr_to_signed_char
 signed char explicit_voidptr_to_signed_char(void *src) {
-  // CHECK: }
   return (signed char)src;
 }
 
 // Implicit truncating conversions from floating-point may result in precision loss.
 // ========================================================================== //
 
 // CHECK-LABEL: @float_to_unsigned_int
 unsigned int float_to_unsigned_int(float src) {
-  // CHECK: }
   return src;
 }
 
 // CHECK-LABEL: @float_to_signed_int
 signed int float_to_signed_int(float src) {
-  // CHECK: }
   return src;
 }
 
 // CHECK-LABEL: @double_to_unsigned_int
 unsigned int double_to_unsigned_int(double src) {
-  // CHECK: }
   return src;
 }
 
 // CHECK-LABEL: @double_to_signed_int
 signed int double_to_signed_int(double src) {
-  // CHECK: }
   return src;
 }
 
 // Implicit truncating conversions between fp may result in precision loss.
 // ========================================================================== //
 
 // CHECK-LABEL: @double_to_float
 float double_to_float(double src) {
-  // CHECK: }
   return src;
 }

test/CodeGen/catch-implicit-signed-integer-truncations-basics-negatives.c

+// RUN: %clang_cc1 -fsanitize=implicit-signed-integer-truncation -fsanitize-recover=implicit-signed-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK
+
+// CHECK-DAG: @[[LINE_100_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 100, i32 10 }, {{.*}}, {{.*}}, i8 2 }
+// CHECK-DAG: @[[LINE_200_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 200, i32 10 }, {{.*}}, {{.*}}, i8 2 }
+
+// CHECK-LABEL: @blacklist_0_convert_signed_int_to_signed_char
+__attribute__((no_sanitize("undefined"))) signed char blacklist_0_convert_signed_int_to_signed_char(signed int x) {
+  // We are not in "undefined" group, so that doesn't work.
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_100_SIGNED_TRUNCATION]] to i8*)
+#line 100
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_1_convert_signed_int_to_signed_char
+__attribute__((no_sanitize("integer"))) signed char blacklist_1_convert_signed_int_to_signed_char(signed int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_2_convert_signed_int_to_signed_char
+__attribute__((no_sanitize("implicit-conversion"))) signed char blacklist_2_convert_signed_int_to_signed_char(signed int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_3_convert_signed_int_to_signed_char
+__attribute__((no_sanitize("implicit-integer-truncation"))) signed char blacklist_3_convert_signed_int_to_signed_char(signed int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_4_convert_signed_int_to_signed_char
+__attribute__((no_sanitize("implicit-signed-integer-truncation"))) signed char blacklist_4_convert_signed_int_to_signed_char(signed int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_5_convert_signed_int_to_signed_char
+__attribute__((no_sanitize("implicit-unsigned-integer-truncation"))) signed char blacklist_5_convert_signed_int_to_signed_char(signed int x) {
+  // This is an signed truncation, not unsigned-one.
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_200_SIGNED_TRUNCATION]] to i8*)
+#line 200
+  return x;
+}

test/CodeGen/catch-implicit-signed-integer-truncations-basics.c

+// RUN: %clang_cc1 -fsanitize=implicit-signed-integer-truncation -fsanitize-recover=implicit-signed-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK
+
+// Test plan:
+//  * Two types - int and char
+//  * Two signs - signed and unsigned
+//  * Square that - we have input and output types.
+// Thus, there are total of (2*2)^2 == 16 tests.
+// These are all the possible variations/combinations of casts.
+// However, not all of them should result in the check.
+// So here, we *only* check which should and which should not result in checks.
+
+// CHECK-DAG: @[[LINE_1100_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 1100, i32 10 }, {{.*}}, {{.*}}, i8 2 }
+// CHECK-DAG: @[[LINE_1500_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 1500, i32 10 }, {{.*}}, {{.*}}, i8 2 }
+// CHECK-DAG: @[[LINE_1600_SIGNED_TRUNCATION:.*]] = {{.*}}, i32 1600, i32 10 }, {{.*}}, {{.*}}, i8 2 }
+
+// CHECK-LABEL: @convert_unsigned_int_to_unsigned_int
+unsigned int convert_unsigned_int_to_unsigned_int(unsigned int x) {
+#line 100
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_char_to_unsigned_char
+unsigned char convert_unsigned_char_to_unsigned_char(unsigned char x) {
+#line 200
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_int_to_signed_int
+signed int convert_signed_int_to_signed_int(signed int x) {
+#line 300
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_char_to_signed_char
+signed char convert_signed_char_to_signed_char(signed char x) {
+#line 400
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_int_to_unsigned_char
+unsigned char convert_unsigned_int_to_unsigned_char(unsigned int x) {
+#line 500
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_char_to_unsigned_int
+unsigned int convert_unsigned_char_to_unsigned_int(unsigned char x) {
+#line 600
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_char_to_signed_int
+signed int convert_unsigned_char_to_signed_int(unsigned char x) {
+#line 700
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_char_to_signed_int
+signed int convert_signed_char_to_signed_int(signed char x) {
+#line 800
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_int_to_signed_int
+signed int convert_unsigned_int_to_signed_int(unsigned int x) {
+#line 900
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_int_to_unsigned_int
+unsigned int convert_signed_int_to_unsigned_int(signed int x) {
+#line 1000
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_int_to_unsigned_char
+unsigned char convert_signed_int_to_unsigned_char(signed int x) {
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1100_SIGNED_TRUNCATION]] to i8*)
+#line 1100
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_char_to_unsigned_char
+unsigned char convert_signed_char_to_unsigned_char(signed char x) {
+#line 1200
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_char_to_signed_char
+signed char convert_unsigned_char_to_signed_char(unsigned char x) {
+#line 1300
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_char_to_unsigned_int
+unsigned int convert_signed_char_to_unsigned_int(signed char x) {
+#line 1400
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_int_to_signed_char
+signed char convert_unsigned_int_to_signed_char(unsigned int x) {
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1500_SIGNED_TRUNCATION]] to i8*)
+#line 1500
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_int_to_signed_char
+signed char convert_signed_int_to_signed_char(signed int x) {
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_1600_SIGNED_TRUNCATION]] to i8*)
+#line 1600
+  return x;
+}

test/CodeGen/catch-implicit-unsigned-integer-truncations-basics-negatives.c

+// RUN: %clang_cc1 -fsanitize=implicit-unsigned-integer-truncation -fsanitize-recover=implicit-unsigned-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK
+
+// CHECK-DAG: @[[LINE_100_UNSIGNED_TRUNCATION:.*]] = {{.*}}, i32 100, i32 10 }, {{.*}}, {{.*}}, i8 1 }
+// CHECK-DAG: @[[LINE_200_UNSIGNED_TRUNCATION:.*]] = {{.*}}, i32 200, i32 10 }, {{.*}}, {{.*}}, i8 1 }
+
+// CHECK-LABEL: @blacklist_0_convert_unsigned_int_to_unsigned_char
+__attribute__((no_sanitize("undefined"))) unsigned char blacklist_0_convert_unsigned_int_to_unsigned_char(unsigned int x) {
+  // We are not in "undefined" group, so that doesn't work.
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_100_UNSIGNED_TRUNCATION]] to i8*)
+#line 100
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_1_convert_unsigned_int_to_unsigned_char
+__attribute__((no_sanitize("integer"))) unsigned char blacklist_1_convert_unsigned_int_to_unsigned_char(unsigned int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_2_convert_unsigned_int_to_unsigned_char
+__attribute__((no_sanitize("implicit-conversion"))) unsigned char blacklist_2_convert_unsigned_int_to_unsigned_char(unsigned int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_3_convert_unsigned_int_to_unsigned_char
+__attribute__((no_sanitize("implicit-integer-truncation"))) unsigned char blacklist_3_convert_unsigned_int_to_unsigned_char(unsigned int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_4_convert_unsigned_int_to_unsigned_char
+__attribute__((no_sanitize("implicit-unsigned-integer-truncation"))) unsigned char blacklist_4_convert_unsigned_int_to_unsigned_char(unsigned int x) {
+  return x;
+}
+
+// CHECK-LABEL: @blacklist_5_convert_unsigned_int_to_unsigned_char
+__attribute__((no_sanitize("implicit-signed-integer-truncation"))) unsigned char blacklist_5_convert_unsigned_int_to_unsigned_char(unsigned int x) {
+  // This is an unsigned truncation, not signed-one.
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_200_UNSIGNED_TRUNCATION]] to i8*)
+#line 200
+  return x;
+}

test/CodeGen/catch-implicit-unsigned-integer-truncations-basics.c

+// RUN: %clang_cc1 -fsanitize=implicit-unsigned-integer-truncation -fsanitize-recover=implicit-unsigned-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s -implicit-check-not="call void @__ubsan_handle_implicit_conversion" --check-prefixes=CHECK
+
+// Test plan:
+//  * Two types - int and char
+//  * Two signs - signed and unsigned
+//  * Square that - we have input and output types.
+// Thus, there are total of (2*2)^2 == 16 tests.
+// These are all the possible variations/combinations of casts.
+// However, not all of them should result in the check.
+// So here, we *only* check which should and which should not result in checks.
+
+// CHECK-DAG: @[[LINE_500_UNSIGNED_TRUNCATION:.*]] = {{.*}}, i32 500, i32 10 }, {{.*}}, {{.*}}, i8 1 }
+
+// CHECK-LABEL: @convert_unsigned_int_to_unsigned_int
+unsigned int convert_unsigned_int_to_unsigned_int(unsigned int x) {
+#line 100
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_char_to_unsigned_char
+unsigned char convert_unsigned_char_to_unsigned_char(unsigned char x) {
+#line 200
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_int_to_signed_int
+signed int convert_signed_int_to_signed_int(signed int x) {
+#line 300
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_char_to_signed_char
+signed char convert_signed_char_to_signed_char(signed char x) {
+#line 400
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_int_to_unsigned_char
+unsigned char convert_unsigned_int_to_unsigned_char(unsigned int x) {
+  // CHECK: call void @__ubsan_handle_implicit_conversion(i8* bitcast ({ {{{.*}}}, {{{.*}}}*, {{{.*}}}*, i8 }* @[[LINE_500_UNSIGNED_TRUNCATION]] to i8*)
+#line 500
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_char_to_unsigned_int
+unsigned int convert_unsigned_char_to_unsigned_int(unsigned char x) {
+#line 600
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_char_to_signed_int
+signed int convert_unsigned_char_to_signed_int(unsigned char x) {
+#line 700
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_char_to_signed_int
+signed int convert_signed_char_to_signed_int(signed char x) {
+#line 800
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_int_to_signed_int
+signed int convert_unsigned_int_to_signed_int(unsigned int x) {
+#line 900
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_int_to_unsigned_int
+unsigned int convert_signed_int_to_unsigned_int(signed int x) {
+#line 1000
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_int_to_unsigned_char
+unsigned char convert_signed_int_to_unsigned_char(signed int x) {
+#line 1100
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_char_to_unsigned_char
+unsigned char convert_signed_char_to_unsigned_char(signed char x) {
+#line 1200
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_char_to_signed_char
+signed char convert_unsigned_char_to_signed_char(unsigned char x) {
+#line 1300
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_char_to_unsigned_int
+unsigned int convert_signed_char_to_unsigned_int(signed char x) {
+#line 1400
+  return x;
+}
+
+// CHECK-LABEL: @convert_unsigned_int_to_signed_char
+signed char convert_unsigned_int_to_signed_char(unsigned int x) {
+#line 1500
+  return x;
+}
+
+// CHECK-LABEL: @convert_signed_int_to_signed_char
+signed char convert_signed_int_to_signed_char(signed int x) {
+#line 1600
+  return x;
+}

test/CodeGenCXX/catch-implicit-integer-truncations.cpp

 // RUN: %clang_cc1 -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefix=CHECK
-// RUN: %clang_cc1 -fsanitize=implicit-integer-truncation -fno-sanitize-recover=implicit-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefixes=CHECK,CHECK-SANITIZE,CHECK-SANITIZE-ANYRECOVER,CHECK-SANITIZE-NORECOVER
-// RUN: %clang_cc1 -fsanitize=implicit-integer-truncation -fsanitize-recover=implicit-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefixes=CHECK,CHECK-SANITIZE,CHECK-SANITIZE-ANYRECOVER,CHECK-SANITIZE-RECOVER
-// RUN: %clang_cc1 -fsanitize=implicit-integer-truncation -fsanitize-trap=implicit-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefixes=CHECK,CHECK-SANITIZE,CHECK-SANITIZE-TRAP
+// RUN: %clang_cc1 -fsanitize=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -fno-sanitize-recover=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefixes=CHECK,CHECK-SANITIZE,CHECK-SANITIZE-ANYRECOVER,CHECK-SANITIZE-NORECOVER
+// RUN: %clang_cc1 -fsanitize=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -fsanitize-recover=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefixes=CHECK,CHECK-SANITIZE,CHECK-SANITIZE-ANYRECOVER,CHECK-SANITIZE-RECOVER
+// RUN: %clang_cc1 -fsanitize=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -fsanitize-trap=implicit-unsigned-integer-truncation,implicit-signed-integer-truncation -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefixes=CHECK,CHECK-SANITIZE,CHECK-SANITIZE-TRAP
 
 extern "C" { // Disable name mangling.
 
 // ========================================================================== //
 // Check that explicit cast does not interfere with implicit conversion
 // ========================================================================== //
 // These contain one implicit truncating conversion, and one explicit truncating cast.
 // We want to make sure that we still diagnose the implicit conversion.

test/Driver/fsanitize.c

 // CHECK-UNDEFINED-WIN-SAME: "-fsanitize={{((signed-integer-overflow|integer-divide-by-zero|float-divide-by-zero|shift-base|shift-exponent|unreachable|return|vla-bound|alignment|null|pointer-overflow|float-cast-overflow|array-bounds|enum|bool|builtin|returns-nonnull-attribute|nonnull-attribute),?){18}"}}
 
 // RUN: %clang -target i386-pc-win32 -fsanitize-coverage=bb %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-COVERAGE-WIN32
 // CHECK-COVERAGE-WIN32: "--dependent-lib={{[^"]*}}ubsan_standalone-i386.lib"
 // RUN: %clang -target x86_64-pc-win32 -fsanitize-coverage=bb %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-COVERAGE-WIN64
 // CHECK-COVERAGE-WIN64: "--dependent-lib={{[^"]*}}ubsan_standalone-x86_64.lib"
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=integer %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-INTEGER -implicit-check-not="-fsanitize-address-use-after-scope"
-// CHECK-INTEGER: "-fsanitize={{((signed-integer-overflow|unsigned-integer-overflow|integer-divide-by-zero|shift-base|shift-exponent|implicit-integer-truncation),?){6}"}}
+// CHECK-INTEGER: "-fsanitize={{((signed-integer-overflow|unsigned-integer-overflow|integer-divide-by-zero|shift-base|shift-exponent|implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){7}"}}
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=implicit-conversion %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-conversion,CHECK-implicit-conversion-RECOVER
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=implicit-conversion -fsanitize-recover=implicit-conversion %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-conversion,CHECK-implicit-conversion-RECOVER
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=implicit-conversion -fno-sanitize-recover=implicit-conversion %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-conversion,CHECK-implicit-conversion-NORECOVER
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=implicit-conversion -fsanitize-trap=implicit-conversion %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-conversion,CHECK-implicit-conversion-TRAP
-// CHECK-implicit-conversion: "-fsanitize={{((implicit-integer-truncation),?){1}"}}
-// CHECK-implicit-conversion-RECOVER: "-fsanitize-recover={{((implicit-integer-truncation),?){1}"}}
-// CHECK-implicit-conversion-RECOVER-NOT: "-fno-sanitize-recover={{((implicit-integer-truncation),?){1}"}}
-// CHECK-implicit-conversion-RECOVER-NOT: "-fsanitize-trap={{((implicit-integer-truncation),?){1}"}}
-// CHECK-implicit-conversion-NORECOVER-NOT: "-fno-sanitize-recover={{((implicit-integer-truncation),?){1}"}} // ???
-// CHECK-implicit-conversion-NORECOVER-NOT: "-fsanitize-recover={{((implicit-integer-truncation),?){1}"}}
-// CHECK-implicit-conversion-NORECOVER-NOT: "-fsanitize-trap={{((implicit-integer-truncation),?){1}"}}
-// CHECK-implicit-conversion-TRAP: "-fsanitize-trap={{((implicit-integer-truncation),?){1}"}}
-// CHECK-implicit-conversion-TRAP-NOT: "-fsanitize-recover={{((implicit-integer-truncation),?){1}"}}
-// CHECK-implicit-conversion-TRAP-NOT: "-fno-sanitize-recover={{((implicit-integer-truncation),?){1}"}}
+// CHECK-implicit-conversion: "-fsanitize={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-conversion-RECOVER: "-fsanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-conversion-RECOVER-NOT: "-fno-sanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-conversion-RECOVER-NOT: "-fsanitize-trap={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-conversion-NORECOVER-NOT: "-fno-sanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}} // ???
+// CHECK-implicit-conversion-NORECOVER-NOT: "-fsanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-conversion-NORECOVER-NOT: "-fsanitize-trap={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-conversion-TRAP: "-fsanitize-trap={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-conversion-TRAP-NOT: "-fsanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-conversion-TRAP-NOT: "-fno-sanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=implicit-integer-truncation %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-integer-truncation,CHECK-implicit-integer-truncation-RECOVER
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=implicit-integer-truncation -fsanitize-recover=implicit-integer-truncation %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-integer-truncation,CHECK-implicit-integer-truncation-RECOVER
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=implicit-integer-truncation -fno-sanitize-recover=implicit-integer-truncation %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-integer-truncation,CHECK-implicit-integer-truncation-NORECOVER
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=implicit-integer-truncation -fsanitize-trap=implicit-integer-truncation %s -### 2>&1 | FileCheck %s --check-prefixes=CHECK-implicit-integer-truncation,CHECK-implicit-integer-truncation-TRAP
+// CHECK-implicit-integer-truncation: "-fsanitize={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-integer-truncation-RECOVER: "-fsanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-integer-truncation-RECOVER-NOT: "-fno-sanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-integer-truncation-RECOVER-NOT: "-fsanitize-trap={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-integer-truncation-NORECOVER-NOT: "-fno-sanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}} // ???
+// CHECK-implicit-integer-truncation-NORECOVER-NOT: "-fsanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-integer-truncation-NORECOVER-NOT: "-fsanitize-trap={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-integer-truncation-TRAP: "-fsanitize-trap={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-integer-truncation-TRAP-NOT: "-fsanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
+// CHECK-implicit-integer-truncation-TRAP-NOT: "-fno-sanitize-recover={{((implicit-unsigned-integer-truncation|implicit-signed-integer-truncation),?){2}"}}
 
 // RUN: %clang -fsanitize=bounds -### -fsyntax-only %s 2>&1 | FileCheck %s --check-prefix=CHECK-BOUNDS
 // CHECK-BOUNDS: "-fsanitize={{((array-bounds|local-bounds),?){2}"}}
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=all %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-FSANITIZE-ALL
 // CHECK-FSANITIZE-ALL: error: unsupported argument 'all' to option 'fsanitize='
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=address,undefined -fno-sanitize=all -fsanitize=thread %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-FNO-SANITIZE-ALL