[llvm] 9542cfa - [JumpTableToSwitch] Fix wrong function used for GUID computation (#192877)

[via llvm-commits]

Author: Alexander Shaposhnikov
Date: 2026-04-19T18:46:48-07:00
New Revision: 9542cfa1ad91c8510904f04fd780e4fcad319694

URL: https://github.com/llvm/llvm-project/commit/9542cfa1ad91c8510904f04fd780e4fcad319694
DIFF: https://github.com/llvm/llvm-project/commit/9542cfa1ad91c8510904f04fd780e4fcad319694.diff

LOG: [JumpTableToSwitch] Fix wrong function used for GUID computation (#192877)

The FuncToGuid lambda's fallback path (when target functions lack !guid
metadata) was using 'F' (the caller) instead of 'Fct' (the callee) in
getIRPGOFuncName, causing all GUID lookups to resolve to the caller's
GUID.

Added: 
    llvm/test/Transforms/JumpTableToSwitch/profile-no-guid-metadata.ll

Modified: 
    llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp b/llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp
index a3e3b9a207ca1..128d23bee20f9 100644
--- a/llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp
@@ -211,11 +211,12 @@ PreservedAnalyses JumpTableToSwitchPass::run(Function &F,
   PostDominatorTree *PDT = AM.getCachedResult<PostDominatorTreeAnalysis>(F);
   DomTreeUpdater DTU(DT, PDT, DomTreeUpdater::UpdateStrategy::Lazy);
   bool Changed = false;
-  auto FuncToGuid = [&](const Function &Fct) {
+  auto FuncToGuid = [InLTO = this->InLTO](const Function &Fct) {
     if (Fct.getMetadata(AssignGUIDPass::GUIDMetadataName))
       return AssignGUIDPass::getGUID(Fct);
 
-    return Function::getGUIDAssumingExternalLinkage(getIRPGOFuncName(F, InLTO));
+    return Function::getGUIDAssumingExternalLinkage(
+        getIRPGOFuncName(Fct, InLTO));
   };
 
   for (BasicBlock &BB : make_early_inc_range(F)) {

diff  --git a/llvm/test/Transforms/JumpTableToSwitch/profile-no-guid-metadata.ll b/llvm/test/Transforms/JumpTableToSwitch/profile-no-guid-metadata.ll
new file mode 100644
index 0000000000000..f4e71c637608a
--- /dev/null
+++ b/llvm/test/Transforms/JumpTableToSwitch/profile-no-guid-metadata.ll
@@ -0,0 +1,61 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
+; RUN: opt < %s -passes=jump-table-to-switch -S | FileCheck %s
+
+;; Test that when target functions lack !guid metadata, the pass correctly
+;; computes GUIDs from the target function names (not the caller's name)
+;; for matching against value profile data. This is a regression test for
+;; a bug where the caller function was used instead of the callee when
+;; computing PGO function names for GUID lookup.
+
+ at jt = constant [2 x ptr] [ptr @jt_target_0, ptr @jt_target_1]
+
+;; Note: these functions intentionally do NOT have !guid metadata,
+;; forcing the pass to compute GUIDs via getIRPGOFuncName.
+define i32 @jt_target_0() {
+; CHECK-LABEL: define i32 @jt_target_0() {
+; CHECK-NEXT:    ret i32 10
+;
+  ret i32 10
+}
+
+define i32 @jt_target_1() {
+; CHECK-LABEL: define i32 @jt_target_1() {
+; CHECK-NEXT:    ret i32 20
+;
+  ret i32 20
+}
+
+define i32 @caller(i32 %idx) {
+; CHECK-LABEL: define i32 @caller(
+; CHECK-SAME: i32 [[IDX:%.*]]) {
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds [2 x ptr], ptr @jt, i32 0, i32 [[IDX]]
+; CHECK-NEXT:    [[FPTR:%.*]] = load ptr, ptr [[GEP]], align 8
+; CHECK-NEXT:    switch i32 [[IDX]], label %[[DEFAULT_SWITCH_CASE_UNREACHABLE:.*]] [
+; CHECK-NEXT:      i32 0, label %[[CALL0:.*]]
+; CHECK-NEXT:      i32 1, label %[[CALL1:.*]]
+; CHECK-NEXT:    ], !prof [[PROF0:![0-9]+]]
+; CHECK:       [[DEFAULT_SWITCH_CASE_UNREACHABLE]]:
+; CHECK-NEXT:    unreachable
+; CHECK:       [[CALL0]]:
+; CHECK-NEXT:    [[TMP1:%.*]] = call i32 @jt_target_0()
+; CHECK-NEXT:    br [[DOTTAIL:label %.*]]
+; CHECK:       [[CALL1]]:
+; CHECK-NEXT:    [[TMP2:%.*]] = call i32 @jt_target_1()
+; CHECK-NEXT:    br [[DOTTAIL]]
+; CHECK:       [[_TAIL:.*:]]
+; CHECK-NEXT:    [[TMP3:%.*]] = phi i32 [ [[TMP1]], %[[CALL0]] ], [ [[TMP2]], %[[CALL1]] ]
+; CHECK-NEXT:    ret i32 [[TMP3]]
+;
+  %gep = getelementptr inbounds [2 x ptr], ptr @jt, i32 0, i32 %idx
+  %fptr = load ptr, ptr %gep
+  %r = call i32 %fptr(), !prof !0
+  ret i32 %r
+}
+
+;; VP metadata: GUID 11912887233601027218 = MD5("jt_target_0"), count 100
+;;              GUID 18156790114353049777 = MD5("jt_target_1"), count 50
+!0 = !{!"VP", i32 0, i64 150, i64 11912887233601027218, i64 100, i64 18156790114353049777, i64 50}
+
+;.
+; CHECK: [[PROF0]] = !{!"branch_weights", i32 0, i32 100, i32 50}
+;.