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[Local] preserve MD_prof in hoistAllInstructionsInto

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This commit is contained in:
Mircea Trofin 2025-08-20 15:04:49 -07:00
parent 961489a611
commit 18cf46f5b8
3 changed files with 26 additions and 10 deletions
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1
llvm/include/llvm/Transforms/Utils/Local.h
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@ -498,6 +498,7 @@ LLVM_ABI void dropDebugUsers(Instruction &I);
///
/// The moved instructions receive the insertion point debug location values
/// (DILocations) and their debug intrinsic instructions are removed.
/// Selects and indirect calls keep their MD_prof metadata.
LLVM_ABI void hoistAllInstructionsInto(BasicBlock *DomBlock,
Instruction *InsertPt, BasicBlock *BB);

14
llvm/lib/Transforms/Utils/Local.cpp
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@ -116,6 +116,8 @@ static cl::opt<unsigned> MaxPhiEntriesIncreaseAfterRemovingEmptyBlock(
cl::desc("Stop removing an empty block if removing it will introduce more "
"than this number of phi entries in its successor"));
extern cl::opt<bool> ProfcheckDisableMetadataFixes;
// Max recursion depth for collectBitParts used when detecting bswap and
// bitreverse idioms.
static const unsigned BitPartRecursionMaxDepth = 48;
@ -3342,8 +3344,11 @@ void llvm::hoistAllInstructionsInto(BasicBlock *DomBlock, Instruction *InsertPt,
// retain their original debug locations (DILocations) and debug intrinsic
// instructions.
//
// Doing so would degrade the debugging experience and adversely affect the
// accuracy of profiling information.
// Doing so would degrade the debugging experience.
//
// FIXME: Issue #152767: debug info should also be the same as the
// original branch, **if** the user explicitly indicated that (for sampling
// PGO)
//
// Currently, when hoisting the instructions, we take the following actions:
// - Remove their debug intrinsic instructions.
@ -3362,7 +3367,10 @@ void llvm::hoistAllInstructionsInto(BasicBlock *DomBlock, Instruction *InsertPt,
for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE;) {
Instruction *I = &*II;
I->dropUBImplyingAttrsAndMetadata();
if (ProfcheckDisableMetadataFixes)
I->dropUBImplyingAttrsAndMetadata();
else
I->dropUBImplyingAttrsAndMetadata({LLVMContext::MD_prof});
if (I->isUsedByMetadata())
dropDebugUsers(*I);
// RemoveDIs: drop debug-info too as the following code does.

21
llvm/test/Transforms/SimplifyCFG/PhiBlockMerge.ll
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@ -1,20 +1,21 @@
; NOTE: Assertions have been autogenerated by update_test_checks.py
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --version 5
; Test merging of blocks that only have PHI nodes in them
;
; RUN: opt < %s -passes=simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s
;
define i32 @test(i1 %a, i1 %b) {
; CHECK-LABEL: @test(
; CHECK: M:
; CHECK-NEXT: [[DOT:%.*]] = select i1 %b, i32 0, i32 1
; CHECK-NEXT: [[W:%.*]] = select i1 %a, i32 2, i32 [[DOT]]
; CHECK-LABEL: define i32 @test(
; CHECK-SAME: i1 [[A:%.*]], i1 [[B:%.*]]) {
; CHECK-NEXT: [[M:.*:]]
; CHECK-NEXT: [[SPEC_SELECT:%.*]] = select i1 [[B]], i32 0, i32 1, !prof [[PROF0:![0-9]+]]
; CHECK-NEXT: [[W:%.*]] = select i1 [[A]], i32 2, i32 [[SPEC_SELECT]], !prof [[PROF1:![0-9]+]]
; CHECK-NEXT: [[R:%.*]] = add i32 [[W]], 1
; CHECK-NEXT: ret i32 [[R]]
;
br i1 %a, label %M, label %O
br i1 %a, label %M, label %O, !prof !0
O: ; preds = %0
br i1 %b, label %N, label %Q
br i1 %b, label %N, label %Q, !prof !1
Q: ; preds = %O
br label %N
N: ; preds = %Q, %O
@ -27,3 +28,9 @@ M: ; preds = %N, %0
ret i32 %R
}
!0 = !{!"branch_weights", i32 11, i32 7}
!1 = !{!"branch_weights", i32 3, i32 5}
;.
; CHECK: [[PROF0]] = !{!"branch_weights", i32 3, i32 5}
; CHECK: [[PROF1]] = !{!"branch_weights", i32 11, i32 7}
;.