[PATCH] D153400: [InstCombine] Add !noundef to match behavior of violating assume

[luxufan via Phabricator via llvm-commits]

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The behaviors of violating assume instruction or !nonnull metadata is
different. The former is immediate undefined behavior, but the latter is
returning poison value. This patch adds !noundef to trigger immediate
undefined behavior if !nonnull is violated.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D153400

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
  llvm/test/Transforms/InstCombine/assume.ll


Index: llvm/test/Transforms/InstCombine/assume.ll
===================================================================
--- llvm/test/Transforms/InstCombine/assume.ll
+++ llvm/test/Transforms/InstCombine/assume.ll
@@ -266,7 +266,7 @@
 
 define i1 @nonnull1(ptr %a) {
 ; CHECK-LABEL: @nonnull1(
-; CHECK-NEXT:    [[LOAD:%.*]] = load ptr, ptr [[A:%.*]], align 8, !nonnull !6
+; CHECK-NEXT:    [[LOAD:%.*]] = load ptr, ptr [[A:%.*]], align 8, !nonnull !6, !noundef !6
 ; CHECK-NEXT:    tail call void @escape(ptr nonnull [[LOAD]])
 ; CHECK-NEXT:    ret i1 false
 ;
Index: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2652,6 +2652,7 @@
         isValidAssumeForContext(II, LHS, &DT)) {
       MDNode *MD = MDNode::get(II->getContext(), std::nullopt);
       LHS->setMetadata(LLVMContext::MD_nonnull, MD);
+      LHS->setMetadata(LLVMContext::MD_noundef, MD);
       return RemoveConditionFromAssume(II);
 
       // TODO: apply nonnull return attributes to calls and invokes


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