[llvm] ab323eb - [SCCP][PredicateInfo] Do not predicate argument of lifetime intrinsic

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2025-08-12T12:56:08+02:00
New Revision: ab323eb0c6b2ed8814c4516d4bce179d55372a5a

URL: https://github.com/llvm/llvm-project/commit/ab323eb0c6b2ed8814c4516d4bce179d55372a5a
DIFF: https://github.com/llvm/llvm-project/commit/ab323eb0c6b2ed8814c4516d4bce179d55372a5a.diff

LOG: [SCCP][PredicateInfo] Do not predicate argument of lifetime intrinsic

Replacing the argument with a no-op bitcast violates a verifier
constraint, even if only temporarily. Any replacement based on it
would result in a violation even after the copy has been removed.

Fixes https://github.com/llvm/llvm-project/issues/153013.

Added: 
    llvm/test/Transforms/SCCP/lifetime.ll

Modified: 
    llvm/lib/Transforms/Utils/PredicateInfo.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/PredicateInfo.cpp b/llvm/lib/Transforms/Utils/PredicateInfo.cpp
index 38a312a3715c9..13c7ad2927d1c 100644
--- a/llvm/lib/Transforms/Utils/PredicateInfo.cpp
+++ b/llvm/lib/Transforms/Utils/PredicateInfo.cpp
@@ -291,6 +291,11 @@ void PredicateInfoBuilder::convertUsesToDFSOrdered(
     Value *Op, SmallVectorImpl<ValueDFS> &DFSOrderedSet) {
   for (auto &U : Op->uses()) {
     if (auto *I = dyn_cast<Instruction>(U.getUser())) {
+      // Lifetime intrinsics must work directly on alloca, do not replace them
+      // with a predicated copy.
+      if (I->isLifetimeStartOrEnd())
+        continue;
+
       ValueDFS VD;
       // Put the phi node uses in the incoming block.
       BasicBlock *IBlock;

diff  --git a/llvm/test/Transforms/SCCP/lifetime.ll b/llvm/test/Transforms/SCCP/lifetime.ll
new file mode 100644
index 0000000000000..2956157725c5f
--- /dev/null
+++ b/llvm/test/Transforms/SCCP/lifetime.ll
@@ -0,0 +1,25 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=ipsccp < %s | FileCheck %s
+
+define void @test() {
+; CHECK-LABEL: define void @test() {
+; CHECK-NEXT:    [[A:%.*]] = alloca [4 x i16], align 2
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq ptr [[A]], inttoptr (i64 -1 to ptr)
+; CHECK-NEXT:    br i1 [[CMP]], label %[[IF:.*]], label %[[EXIT:.*]]
+; CHECK:       [[IF]]:
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0(ptr [[A]])
+; CHECK-NEXT:    br label %[[EXIT]]
+; CHECK:       [[EXIT]]:
+; CHECK-NEXT:    ret void
+;
+  %a = alloca [4 x i16]
+  %cmp = icmp eq ptr %a, inttoptr (i64 -1 to ptr)
+  br i1 %cmp, label %if, label %exit
+
+if:
+  call void @llvm.lifetime.start.p0(ptr %a)
+  br label %exit
+
+exit:
+  ret void
+}