[llvm] 7fc0efd - [InstCombine] Add !noundef to match behavior of violating assume

[via llvm-commits]

Author: luxufan
Date: 2023-06-21T23:17:57+08:00
New Revision: 7fc0efd0dc4d748ee1e1273f8afec289763c5049

URL: https://github.com/llvm/llvm-project/commit/7fc0efd0dc4d748ee1e1273f8afec289763c5049
DIFF: https://github.com/llvm/llvm-project/commit/7fc0efd0dc4d748ee1e1273f8afec289763c5049.diff

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

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.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D153400

Added: 
    

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

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 0c695109654c4..c30c56a418ca5 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2652,6 +2652,7 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
         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

diff  --git a/llvm/test/Transforms/InstCombine/assume.ll b/llvm/test/Transforms/InstCombine/assume.ll
index bd909ad582e18..48095cf8b13b1 100644
--- a/llvm/test/Transforms/InstCombine/assume.ll
+++ b/llvm/test/Transforms/InstCombine/assume.ll
@@ -266,7 +266,7 @@ define i32 @bundle2(ptr %P) {
 
 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
 ;