[PATCH] D87306: [AttributeFuncs] Consider `noundef` in `typeIncompatible`

[Johannes Doerfert via Phabricator via llvm-commits]

jdoerfert created this revision.
jdoerfert added a reviewer: fhahn.
Herald added subscribers: bollu, hiraditya.
Herald added a project: LLVM.
jdoerfert requested review of this revision.

Drop `noundef` for return values that are replaced by void and make it
illegal to put `noundef` on a void value.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D87306

Files:
  llvm/lib/IR/Attributes.cpp
  llvm/test/Transforms/DeadArgElim/returned.ll
  llvm/test/Verifier/noundef.ll


Index: llvm/test/Verifier/noundef.ll
===================================================================
--- /dev/null
+++ llvm/test/Verifier/noundef.ll
@@ -0,0 +1,7 @@
+; RUN: not llvm-as < %s -o /dev/null 2>&1 | FileCheck %s
+
+; CHECK: Wrong types for attribute: inalloca nest noalias nocapture noundef nonnull readnone readonly signext sret zeroext byref(void) byval(void) preallocated(void) align 1 dereferenceable(1) dereferenceable_or_null(1)
+; CHECK-NEXT: @noundef_void
+define noundef void @noundef_void() {
+  ret void
+}
Index: llvm/test/Transforms/DeadArgElim/returned.ll
===================================================================
--- llvm/test/Transforms/DeadArgElim/returned.ll
+++ llvm/test/Transforms/DeadArgElim/returned.ll
@@ -45,7 +45,7 @@
 
 ; Drop all these attributes
 ; CHECK-LABEL: define internal void @test6
-define internal align 8 dereferenceable_or_null(2) noalias i8* @test6() {
+define internal align 8 dereferenceable_or_null(2) noundef noalias i8* @test6() {
   ret i8* null
 }
 
Index: llvm/lib/IR/Attributes.cpp
===================================================================
--- llvm/lib/IR/Attributes.cpp
+++ llvm/lib/IR/Attributes.cpp
@@ -1859,6 +1859,10 @@
         .addByValAttr(Ty)
         .addByRefAttr(Ty);
 
+  // Some attributes can apply to all "values" but there are no `void` values.
+  if (Ty->isVoidTy())
+    Incompatible.addAttribute(Attribute::NoUndef);
+
   return Incompatible;
 }
 


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