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[SimplifyCFG] Don't propagate weights to unconditional branches in turnSwitchRangeIntoICmp #165931

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Merged
merged 2 commits into from
Oct 31, 2025
Merged

[SimplifyCFG] Don't propagate weights to unconditional branches in turnSwitchRangeIntoICmp #165931

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8a24df8
[SimplifyCFG] Don't propagate weights to unconditional branches in `t…
mtrofin Oct 31, 2025
39f1cc7
Merge branch 'main' into users/mtrofin/10-31-_simplifycfg_don_t_propa…
mtrofin Oct 31, 2025
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2 changes: 1 addition & 1 deletion llvm/lib/Transforms/Utils/SimplifyCFG.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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()) {
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13 changes: 9 additions & 4 deletions llvm/test/Transforms/SimplifyCFG/pr165301.ll
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@@ -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]]:
Expand All @@ -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}
;.
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