[BuildLibCalls] Add noundef to allocator fns' size

[aqjune]

Summary

This is a patch to explicitly mark the size parameter of allocator functions like malloc/realloc/... as noundef.

For C/C++: undef can be created from reading an uninitialized variable or padding.
Calling a function with uninitialized variable is already UB.
Calling malloc with padding value is.. something that's not expected. Padding bits may appear in a coerced aggregate, which doesn't apply to malloc's size.
Therefore, malloc's size can be marked as noundef.

For transformations that introduce malloc/realloc/..: I ran LLVM unit tests with an updated Alive2 semantics, and found no regression, so it seems okay.

[aqjune]

I wanted to add noundef to C++ new operators, but a former discussion said attributes of these should be inserted by the frontend.
Since I wasn't friendly with the clang code, I found Sema::FindAllocationFunctions which lists possible new operator functions and matches the right one, but couldn't find the place that actually adds attributes to these.
A question is - there is already an ongoing effort for adding noundef to C/C++ function arguments, and would it automatically resolve this case? Otherwise, where should I update to add noundef to new operator arguments?

[jdoerfert]

LG

[tra]

FYI, this change broke CUDA compilation with recent CUDA versions (versions before CUDA-10.2 seem to work). I don't know what wexactly went wrong yet.

http://lab.llvm.org:8011/#/builders/1/builds/6671

[tra]

In D97045#2582287, @tra wrote:

FYI, this change broke CUDA compilation with recent CUDA versions (versions before CUDA-10.2 seem to work). I don't know what wexactly went wrong yet.

http://lab.llvm.org:8011/#/builders/1/builds/6671

False alarm. The bots were failing due to an unrelated infrastructure change.

[aqjune]

Okay, thanks for letting me know..!

llvm/lib/Transforms/Utils/BuildLibCalls.cpp

if (!F.hasParamAttribute(ArgNo, Attribute::NoUndef)) {
       F.addParamAttr(ArgNo, Attribute::NoUndef);
       ++NumNoUndef;
       Changed = true;
     }
   }
   return Changed;
 }
 
+static bool setArgNoUndef(Function &F, unsigned ArgNo) {
+  if (F.hasParamAttribute(ArgNo, Attribute::NoUndef))
+    return false;
+  F.addParamAttr(ArgNo, Attribute::NoUndef);
+  ++NumNoUndef;
+  return true;
+}
+
 static bool setRetAndArgsNoUndef(Function &F) {
   return setRetNoUndef(F) | setArgsNoUndef(F);
 }
 
 static bool setReturnedArg(Function &F, unsigned ArgNo) {
   if (F.hasParamAttribute(ArgNo, Attribute::Returned))
     return false;
   F.addParamAttr(ArgNo, Attribute::Returned);
case LibFunc_scanf:
     Changed |= setOnlyReadsMemory(F, 0);
     return Changed;
   case LibFunc_setbuf:
   case LibFunc_setvbuf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 0);
     return Changed;
-  case LibFunc_strdup:
   case LibFunc_strndup:
+    Changed |= setArgNoUndef(F, 1);
+    LLVM_FALLTHROUGH;
+  case LibFunc_strdup:
     Changed |= setOnlyAccessesInaccessibleMemOrArgMem(F);
     Changed |= setDoesNotThrow(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     return Changed;
   case LibFunc_stat:
case LibFunc_system:
     // May throw; "system" is a valid pthread cancellation point.
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     return Changed;
   case LibFunc_malloc:
   case LibFunc_vec_malloc:
     Changed |= setOnlyAccessesInaccessibleMemory(F);
-    Changed |= setRetNoUndef(F);
+    Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     return Changed;
   case LibFunc_memcmp:
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotThrow(F);
bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
   case LibFunc_realloc:
   case LibFunc_vec_realloc:
     Changed |= setOnlyAccessesInaccessibleMemOrArgMem(F);
     Changed |= setRetNoUndef(F);
     Changed |= setDoesNotThrow(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
+    Changed |= setArgNoUndef(F, 1);
     return Changed;
   case LibFunc_reallocf:
     Changed |= setRetNoUndef(F);
     Changed |= setWillReturn(F);
+    Changed |= setArgNoUndef(F, 1);
     return Changed;
   case LibFunc_read:
     // May throw; "read" is a valid pthread cancellation point.
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotCapture(F, 1);
     return Changed;
   case LibFunc_rewind:
     Changed |= setRetAndArgsNoUndef(F);
bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
   case LibFunc_write:
     // May throw; "write" is a valid pthread cancellation point.
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);
     return Changed;
   case LibFunc_aligned_alloc:
     Changed |= setOnlyAccessesInaccessibleMemory(F);
-    Changed |= setRetNoUndef(F);
+    Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     return Changed;
   case LibFunc_bcopy:
     Changed |= setDoesNotThrow(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
case LibFunc_bzero:
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyWritesMemory(F, 0);
     return Changed;
   case LibFunc_calloc:
   case LibFunc_vec_calloc:
     Changed |= setOnlyAccessesInaccessibleMemory(F);
-    Changed |= setRetNoUndef(F);
+    Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     return Changed;
   case LibFunc_chmod:
   case LibFunc_chown:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
case LibFunc_vfscanf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);
     return Changed;
   case LibFunc_valloc:
     Changed |= setOnlyAccessesInaccessibleMemory(F);
-    Changed |= setRetNoUndef(F);
+    Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     return Changed;
   case LibFunc_vprintf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 0);
case LibFunc_lchown:
     Changed |= setOnlyReadsMemory(F, 0);
     return Changed;
   case LibFunc_qsort:
     // May throw; places call through function pointer.
     // Cannot give undef pointer/size
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotCapture(F, 3);
     return Changed;
-  case LibFunc_dunder_strdup:
   case LibFunc_dunder_strndup:
+    Changed |= setArgNoUndef(F, 1);
+    LLVM_FALLTHROUGH;
+  case LibFunc_dunder_strdup:
     Changed |= setDoesNotThrow(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     return Changed;
   case LibFunc_dunder_strtok_r:
     Changed |= setDoesNotThrow(F);

llvm/test/Transforms/InferFunctionAttrs/annotate.ll

 declare float @acoshf(float)
 
 ; CHECK: declare x86_fp80 @acoshl(x86_fp80) [[NOFREE_NOUNWIND_WILLRETURN]]
 declare x86_fp80 @acoshl(x86_fp80)
 
 ; CHECK: declare x86_fp80 @acosl(x86_fp80) [[NOFREE_NOUNWIND_WILLRETURN]]
 declare x86_fp80 @acosl(x86_fp80)
 
-; CHECK: declare noalias noundef i8* @aligned_alloc(i64, i64) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND:#[0-9]+]]
+; CHECK: declare noalias noundef i8* @aligned_alloc(i64 noundef, i64 noundef) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND:#[0-9]+]]
 declare i8* @aligned_alloc(i64, i64)
 
 ; CHECK: declare double @asin(double) [[NOFREE_NOUNWIND_WILLRETURN]]
 declare double @asin(double)
 
 ; CHECK: declare float @asinf(float) [[NOFREE_NOUNWIND_WILLRETURN]]
 declare float @asinf(float)
 

 declare i32 @bcmp(i8*, i8*, i64)
 
 ; CHECK: declare void @bcopy(i8* nocapture readonly, i8* nocapture writeonly, i64)  [[ARGMEMONLY_NOFREE_NOUNWIND:#[0-9]+]]
 declare void @bcopy(i8*, i8*, i64)
 
 ; CHECK: declare void @bzero(i8* nocapture writeonly, i64)  [[ARGMEMONLY_NOFREE_NOUNWIND:#[0-9]+]]
 declare void @bzero(i8*, i64)
 
-; CHECK: declare noalias noundef i8* @calloc(i64, i64) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN:#[0-9]+]]
+; CHECK: declare noalias noundef i8* @calloc(i64 noundef, i64 noundef) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN:#[0-9]+]]
 declare i8* @calloc(i64, i64)
 
 ; CHECK: declare double @cbrt(double) [[NOFREE_NOUNWIND_WILLRETURN]]
 declare double @cbrt(double)
 
 ; CHECK: declare float @cbrtf(float) [[NOFREE_NOUNWIND_WILLRETURN]]
 declare float @cbrtf(float)
 

 declare x86_fp80 @logl(x86_fp80)
 
 ; CHECK: declare noundef i32 @lstat(i8* nocapture noundef readonly, %opaque* nocapture noundef) [[NOFREE_NOUNWIND]]
 declare i32 @lstat(i8*, %opaque*)
 
 ; CHECK-LINUX: declare noundef i32 @lstat64(i8* nocapture noundef readonly, %opaque* nocapture noundef) [[NOFREE_NOUNWIND]]
 declare i32 @lstat64(i8*, %opaque*)
 
-; CHECK: declare noalias noundef i8* @malloc(i64) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN]]
+; CHECK: declare noalias noundef i8* @malloc(i64 noundef) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN]]
 declare i8* @malloc(i64)
 
 ; CHECK-LINUX: declare noalias noundef i8* @memalign(i64, i64) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN]]
 declare i8* @memalign(i64, i64)
 
 ; CHECK: declare i8* @memccpy(i8* noalias writeonly, i8* noalias nocapture readonly, i32, i64) [[ARGMEMONLY_NOFREE_NOUNWIND:#[0-9]+]]
 declare i8* @memccpy(i8*, i8*, i32, i64)
 

 declare void @qsort(i8*, i64, i64, i32 (i8*, i8*)*)
 
 ; CHECK: declare noundef i64 @read(i32 noundef, i8* nocapture noundef, i64 noundef) [[NOFREE]]
 declare i64 @read(i32, i8*, i64)
 
 ; CHECK: declare noundef i64 @readlink(i8* nocapture noundef readonly, i8* nocapture noundef, i64 noundef) [[NOFREE_NOUNWIND]]
 declare i64 @readlink(i8*, i8*, i64)
 
-; CHECK: declare noalias noundef i8* @realloc(i8* nocapture, i64) [[NOUNWIND]]
+; CHECK: declare noalias noundef i8* @realloc(i8* nocapture, i64 noundef) [[NOUNWIND]]
 declare i8* @realloc(i8*, i64)
 
-; CHECK: declare noundef i8* @reallocf(i8*, i64)
+; CHECK: declare noundef i8* @reallocf(i8*, i64 noundef)
 declare i8* @reallocf(i8*, i64)
 
 ; CHECK: declare noundef i8* @realpath(i8* nocapture noundef readonly, i8* noundef) [[NOFREE_NOUNWIND]]
 declare i8* @realpath(i8*, i8*)
 
 ; CHECK: declare noundef i32 @remove(i8* nocapture noundef readonly) [[NOFREE_NOUNWIND]]
 declare i32 @remove(i8*)
 

 declare i8* @strncat(i8*, i8*, i64)
 
 ; CHECK: declare i32 @strncmp(i8* nocapture, i8* nocapture, i64) [[ARGMEMONLY_NOFREE_NOUNWIND_READONLY]]
 declare i32 @strncmp(i8*, i8*, i64)
 
 ; CHECK: declare i8* @strncpy(i8* noalias returned writeonly, i8* noalias nocapture readonly, i64) [[ARGMEMONLY_NOFREE_NOUNWIND]]
 declare i8* @strncpy(i8*, i8*, i64)
 
-; CHECK: declare noalias i8* @strndup(i8* nocapture readonly, i64) [[INACCESSIBLEMEMORARGONLY_NOFREE_NOUNWIND_WILLRETURN]]
+; CHECK: declare noalias i8* @strndup(i8* nocapture readonly, i64 noundef) [[INACCESSIBLEMEMORARGONLY_NOFREE_NOUNWIND_WILLRETURN]]
 declare i8* @strndup(i8*, i64)
 
 ; CHECK: declare i64 @strnlen(i8*, i64) [[NOFREE_NOUNWIND_WILLRETURN]]
 declare i64 @strnlen(i8*, i64)
 
 ; CHECK: declare i8* @strpbrk(i8*, i8* nocapture) [[ARGMEMONLY_NOFREE_NOUNWIND:#[0-9]+]]
 declare i8* @strpbrk(i8*, i8*)
 

 declare i32 @unsetenv(i8*)
 
 ; CHECK: declare noundef i32 @utime(i8* nocapture noundef readonly, %opaque* nocapture noundef readonly) [[NOFREE_NOUNWIND]]
 declare i32 @utime(i8*, %opaque*)
 
 ; CHECK: declare noundef i32 @utimes(i8* nocapture noundef readonly, %opaque* nocapture noundef readonly) [[NOFREE_NOUNWIND]]
 declare i32 @utimes(i8*, %opaque*)
 
-; CHECK: declare noalias noundef i8* @valloc(i64) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN]]
+; CHECK: declare noalias noundef i8* @valloc(i64 noundef) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN]]
 declare i8* @valloc(i64)
 
 ; CHECK: declare noundef i32 @vfprintf(%opaque* nocapture noundef, i8* nocapture noundef readonly, %opaque* noundef) [[NOFREE_NOUNWIND]]
 declare i32 @vfprintf(%opaque*, i8*, %opaque*)
 
 ; CHECK: declare noundef i32 @vfscanf(%opaque* nocapture noundef, i8* nocapture noundef readonly, %opaque* noundef) [[NOFREE_NOUNWIND]]
 declare i32 @vfscanf(%opaque*, i8*, %opaque*)