[llvm-branch-commits] [llvm] 97dd922 - Don't infer attributes on '::operator new'.

[Tom Stellard via llvm-branch-commits]

Author: Richard Smith
Date: 2021-02-12T16:37:18-08:00
New Revision: 97dd9224f1033b1d6313ae80047e48ff964ca77d

URL: https://github.com/llvm/llvm-project/commit/97dd9224f1033b1d6313ae80047e48ff964ca77d
DIFF: https://github.com/llvm/llvm-project/commit/97dd9224f1033b1d6313ae80047e48ff964ca77d.diff

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

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.

(cherry picked from commit ab243efb261ba7e27f4b14e1a6fbbff15a79c0bf)

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/BuildLibCalls.cpp
    llvm/test/Transforms/InferFunctionAttrs/annotate.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
index 811b9c04906d..dba5403f272a 100644
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -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:

diff  --git a/llvm/test/Transforms/InferFunctionAttrs/annotate.ll b/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
index 0af18151d6f6..5c6ec0b683ca 100644
--- a/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
+++ b/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
@@ -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 }