[llvm] [SimplifyCFG] Don't propagate weights to unconditional branches in `turnSwitchRangeIntoICmp` (PR #165931)

[Mircea Trofin via llvm-commits]

https://github.com/mtrofin updated https://github.com/llvm/llvm-project/pull/165931

>From 8a24df848a14ddb1d2f471b783c8558487597d17 Mon Sep 17 00:00:00 2001
From: Mircea Trofin <mtrofin at google.com>
Date: Fri, 31 Oct 2025 15:29:22 -0700
Subject: [PATCH] [SimplifyCFG] Don't propagate weights to unconditional
 branches in `turnSwitchRangeIntoICmp`

---
 llvm/lib/Transforms/Utils/SimplifyCFG.cpp    |  2 +-
 llvm/test/Transforms/SimplifyCFG/pr165301.ll | 13 +++++++++----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 6addcfab15125..cbc604e87cf1a 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -5956,7 +5956,7 @@ bool SimplifyCFGOpt::turnSwitchRangeIntoICmp(SwitchInst *SI,
   }
 
   // Update weight for the newly-created conditional branch.
-  if (hasBranchWeightMD(*SI)) {
+  if (hasBranchWeightMD(*SI) && NewBI->isConditional()) {
     SmallVector<uint64_t, 8> Weights;
     getBranchWeights(SI, Weights);
     if (Weights.size() == 1 + SI->getNumCases()) {
diff --git a/llvm/test/Transforms/SimplifyCFG/pr165301.ll b/llvm/test/Transforms/SimplifyCFG/pr165301.ll
index 4a539d77af3cb..1df655250f57e 100644
--- a/llvm/test/Transforms/SimplifyCFG/pr165301.ll
+++ b/llvm/test/Transforms/SimplifyCFG/pr165301.ll
@@ -1,11 +1,11 @@
-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --version 6
 ; RUN: opt -S -passes="simplifycfg<switch-range-to-icmp>" < %s | FileCheck %s
 
 ; Make sure there's no use after free when removing incoming values from PHI nodes
 
-define i32 @pr165301(i1 %cond) {
+define i32 @pr165301(i1 %cond) !prof !0 {
 ; CHECK-LABEL: define i32 @pr165301(
-; CHECK-SAME: i1 [[COND:%.*]]) {
+; CHECK-SAME: i1 [[COND:%.*]]) !prof [[PROF0:![0-9]+]] {
 ; CHECK-NEXT:  [[ENTRY:.*:]]
 ; CHECK-NEXT:    br label %[[SWITCHBB:.*]]
 ; CHECK:       [[SWITCHBB]]:
@@ -18,9 +18,14 @@ switchbb:
   switch i1 %cond, label %default [
   i1 false, label %switchbb
   i1 true, label %switchbb
-  ]
+  ], !prof !1
 
 default:
   %phi.lcssa = phi i32 [ 0, %switchbb ]
   ret i32 %phi.lcssa
 }
+!0 = !{!"function_entry_count", i32 10}
+!1 = !{!"branch_weights", i32 2, i32 3, i32 5}
+;.
+; CHECK: [[PROF0]] = !{!"function_entry_count", i32 10}
+;.