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Don't infer attributes on '::operator new'.

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These attributes were all incorrect or inappropriate for LLVM to infer:
- inaccessiblememonly is generally wrong; user replacement operator new
  can access memory that's visible to the caller, as can a new_handler
  function.
- willreturn is generally wrong; a custom new_handler is not guaranteed
  to terminate.
- noalias is inappropriate: Clang has a flag to determine whether this
  attribute should be present and adds it itself when appropriate.
- noundef and nonnull on the return value should be specified by the
  frontend on all 'operator new' functions if we want them, not here.

In any case, inferring attributes on functions declared 'nobuiltin' (as
these are when Clang emits them) seems questionable.
This commit is contained in:
Richard Smith 2021-02-04 13:55:28 -08:00
parent c07a815edb
commit 8a8273062f
2 changed files with 0 additions and 31 deletions
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25
lib/Transforms/Utils/BuildLibCalls.cpp
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@ -170,16 +170,6 @@ static bool setRetAndArgsNoUndef(Function &F) {
return setRetNoUndef(F) | setArgsNoUndef(F);
}
static bool setRetNonNull(Function &F) {
assert(F.getReturnType()->isPointerTy() &&
"nonnull applies only to pointers");
if (F.hasAttribute(AttributeList::ReturnIndex, Attribute::NonNull))
return false;
F.addAttribute(AttributeList::ReturnIndex, Attribute::NonNull);
++NumNonNull;
return true;
}
static bool setReturnedArg(Function &F, unsigned ArgNo) {
if (F.hasParamAttribute(ArgNo, Attribute::Returned))
return false;
@ -1005,21 +995,6 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
Changed |= setDoesNotCapture(F, 0);
Changed |= setDoesNotCapture(F, 1);
return Changed;
case LibFunc_Znwj: // new(unsigned int)
case LibFunc_Znwm: // new(unsigned long)
case LibFunc_Znaj: // new[](unsigned int)
case LibFunc_Znam: // new[](unsigned long)
case LibFunc_msvc_new_int: // new(unsigned int)
case LibFunc_msvc_new_longlong: // new(unsigned long long)
case LibFunc_msvc_new_array_int: // new[](unsigned int)
case LibFunc_msvc_new_array_longlong: // new[](unsigned long long)
Changed |= setOnlyAccessesInaccessibleMemory(F);
// Operator new always returns a nonnull noalias pointer
Changed |= setRetNoUndef(F);
Changed |= setRetNonNull(F);
Changed |= setRetDoesNotAlias(F);
Changed |= setWillReturn(F);
return Changed;
// TODO: add LibFunc entries for:
// case LibFunc_memset_pattern4:
// case LibFunc_memset_pattern8:

6
test/Transforms/InferFunctionAttrs/annotate.ll
View File

@ -4,12 +4,6 @@
; RUN: opt < %s -mtriple=x86_64-unknown-linux-gnu -inferattrs -S | FileCheck -check-prefix=CHECK -check-prefix=CHECK-LINUX %s
; RUN: opt < %s -mtriple=nvptx -inferattrs -S | FileCheck -check-prefix=CHECK-NVPTX %s
; operator new routines
declare i8* @_Znwj(i64 )
; CHECK: declare noalias noundef nonnull i8* @_Znwj(i64) [[INACCESSIBLEMEMONLY_NOFREE_WILLRETURN:#[0-9]+]]
declare i8* @_Znwm(i64)
; CHECK: declare noalias noundef nonnull i8* @_Znwm(i64) [[INACCESSIBLEMEMONLY_NOFREE_WILLRETURN]]
declare i32 @__nvvm_reflect(i8*)
; CHECK-NVPTX: declare noundef i32 @__nvvm_reflect(i8* noundef) [[NOFREE_NOUNWIND_READNONE:#[0-9]+]]
; CHECK-NVPTX: attributes [[NOFREE_NOUNWIND_READNONE]] = { nofree nounwind readnone }