CodeGen: Let arrays be inputs to inline asm

[majnemer]

Summary

An array showing up in an inline assembly input is accepted in ICC and
GCC 4.8

This fixes PR20201.

[rsmith]

2014-07-04 1:07 GMT-07:00 David Majnemer <[e-mail]>:

Hi rsmith, rnk,

An array showing up in an inline assembly input is accepted in ICC and
GCC 4.8

This fixes PR20201.

http://reviews.llvm.org/D4382

Files:

lib/CodeGen/CGExpr.cpp
test/CodeGen/asm.c
test/CodeGen/x86-64-inline-asm.c

Index: lib/CodeGen/CGExpr.cpp

• lib/CodeGen/CGExpr.cpp

+++ lib/CodeGen/CGExpr.cpp
@@ -2781,7 +2781,6 @@

switch (E->getCastKind()) {
case CK_ToVoid:
case CK_BitCast:

• case CK_ArrayToPointerDecay:

As discussed in person, I think this is addressing the symptom rather than
the cause. A memory operand expects an lvalue, and we're incorrectly
performing an lvalue-to-rvalue conversion on it in Sema.

case CK_FunctionToPointerDecay:
case CK_NullToMemberPointer:
case CK_NullToPointer:

@@ -2836,6 +2835,7 @@

  return MakeAddrLValue(EmitDynamicCast(V, DCE), E->getType());
}

+ case CK_ArrayToPointerDecay:

case CK_ConstructorConversion:
case CK_UserDefinedConversion:
case CK_CPointerToObjCPointerCast:

Index: test/CodeGen/asm.c

• test/CodeGen/asm.c

+++ test/CodeGen/asm.c
@@ -239,3 +239,12 @@
// CHECK: call void asm sideeffect "/* $0 */",
"i|r,~{dirflag},~{fpsr},~{flags}"(i32 1)
}

+static unsigned t29_var[1];
+
+void t29(void) {
+ asm volatile("movl %%eax, %0"
+ :
+ : "m"(t29_var));
+ CHECK: @t29
+ CHECK: call void asm sideeffect "movl %eax, $0",
"*m,~{dirflag},~{fpsr},~{flags}"([1 x i32]* @t29_var)
+}

Index: test/CodeGen/x86-64-inline-asm.c

• test/CodeGen/x86-64-inline-asm.c

+++ test/CodeGen/x86-64-inline-asm.c
@@ -10,3 +10,8 @@
// expected-error@-5 {{scale factor without index register is ignored}}
#endif
}
+
+static unsigned var[1] = {};
+void g(void) { asm volatile("movd %%xmm0, %0"
+ :
+ : "m"(var)); }

[majnemer]

• This is a Sema bug, not a CodeGen bug.

[majnemer]

• Remove changes from CodeGen.

[rnk]

lgtm, but please wait for http://crbug.com/391927 in libyuv to be resolved.

[rnk]

Looks like we can land this now.

[majnemer]

Closed by commit rL212954 (authored by @majnemer).

lib/CodeGen/CGExpr.cpp

 /// then it must mean that we need the address of an aggregate in order to
 /// access one of its members.  This can happen for all the reasons that casts
 /// are permitted with aggregate result, including noop aggregate casts, and
 /// cast from scalar to union.
 LValue CodeGenFunction::EmitCastLValue(const CastExpr *E) {
   switch (E->getCastKind()) {
   case CK_ToVoid:
   case CK_BitCast:
-  case CK_ArrayToPointerDecay:
   case CK_FunctionToPointerDecay:
   case CK_NullToMemberPointer:
   case CK_NullToPointer:
   case CK_IntegralToPointer:
   case CK_PointerToIntegral:
   case CK_PointerToBoolean:
   case CK_VectorSplat:
   case CK_IntegralCast:
LValue CodeGenFunction::EmitCastLValue(const CastExpr *E) {
 
   case CK_Dynamic: {
     LValue LV = EmitLValue(E->getSubExpr());
     llvm::Value *V = LV.getAddress();
     const auto *DCE = cast<CXXDynamicCastExpr>(E);
     return MakeAddrLValue(EmitDynamicCast(V, DCE), E->getType());
   }
 
+  case CK_ArrayToPointerDecay:
   case CK_ConstructorConversion:
   case CK_UserDefinedConversion:
   case CK_CPointerToObjCPointerCast:
   case CK_BlockPointerToObjCPointerCast:
   case CK_NoOp:
   case CK_LValueToRValue:
     return EmitLValue(E->getSubExpr());
 

lib/Sema/SemaStmtAsm.cpp

for (unsigned i = NumOutputs, e = NumOutputs + NumInputs; i != e; i++) {
 
     // Only allow void types for memory constraints.
     if (Info.allowsMemory() && !Info.allowsRegister()) {
       if (CheckAsmLValue(InputExpr, *this))
         return StmtError(Diag(InputExpr->getLocStart(),
                               diag::err_asm_invalid_lvalue_in_input)
                          << Info.getConstraintStr()
                          << InputExpr->getSourceRange());
+    } else {
+      ExprResult Result = DefaultFunctionArrayLvalueConversion(Exprs[i]);
+      if (Result.isInvalid())
+        return StmtError();
+
+      Exprs[i] = Result.get();
     }
 
     if (Info.allowsRegister()) {
       if (InputExpr->getType()->isVoidType()) {
         return StmtError(Diag(InputExpr->getLocStart(),
                               diag::err_asm_invalid_type_in_input)
           << InputExpr->getType() << Info.getConstraintStr()
           << InputExpr->getSourceRange());
       }
     }
 
-    ExprResult Result = DefaultFunctionArrayLvalueConversion(Exprs[i]);
-    if (Result.isInvalid())
-      return StmtError();
-
-    Exprs[i] = Result.get();
     InputConstraintInfos.push_back(Info);
 
     const Type *Ty = Exprs[i]->getType().getTypePtr();
     if (Ty->isDependentType())
       continue;
 
     if (!Ty->isVoidType() || !Info.allowsMemory())
       if (RequireCompleteType(InputExpr->getLocStart(), Exprs[i]->getType(),

test/CodeGen/asm.c

 // Check handling of '*' and '#' constraint modifiers.
 void t28(void)
 {
   asm volatile ("/* %0 */" : : "i#*X,*r" (1));
 // CHECK: @t28
 // CHECK: call void asm sideeffect "/* $0 */", "i|r,~{dirflag},~{fpsr},~{flags}"(i32 1)
 }
 
+static unsigned t29_var[1];
+
+void t29(void) {
+  asm volatile("movl %%eax, %0"
+               :
+               : "m"(t29_var));
+  // CHECK: @t29
+  // CHECK: call void asm sideeffect "movl %eax, $0", "*m,~{dirflag},~{fpsr},~{flags}"([1 x i32]* @t29_var)
+}

test/CodeGen/x86-64-inline-asm.c

 // REQUIRES: x86-registered-target
 // RUN: %clang_cc1 -triple x86_64 %s -S -o /dev/null -DWARN -verify
 // RUN: %clang_cc1 -triple x86_64 %s -S -o /dev/null -Werror -verify
 void f() {
   asm("movaps %xmm3, (%esi, 2)");
 // expected-note@1 {{instantiated into assembly here}}
 #ifdef WARN
 // expected-warning@-3 {{scale factor without index register is ignored}}
 #else
 // expected-error@-5 {{scale factor without index register is ignored}}
 #endif
 }
+
+static unsigned var[1] = {};
+void g(void) { asm volatile("movd %%xmm0, %0"
+                            :
+                            : "m"(var)); }