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[KeyInstr][JumpThreading] Remap atoms duping bb with cond br on phi into pred

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See test for details.
This commit is contained in:
Orlando Cazalet-Hyams 2025-03-25 15:24:05 +00:00
parent 272f806606
commit 6488f4bca6
2 changed files with 96 additions and 0 deletions
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9
llvm/lib/Transforms/Scalar/JumpThreading.cpp
View File

@ -2683,6 +2683,9 @@ bool JumpThreadingPass::duplicateCondBranchOnPHIIntoPred(
// PredBB block. Evaluate PHI nodes in BB.
ValueToValueMapTy ValueMapping;
// Remember the position before the inserted instructions.
auto RItBeforeInsertPt = std::next(OldPredBranch->getReverseIterator());
BasicBlock::iterator BI = BB->begin();
for (; PHINode *PN = dyn_cast<PHINode>(BI); ++BI)
ValueMapping[PN] = PN->getIncomingValueForBlock(PredBB);
@ -2702,6 +2705,8 @@ bool JumpThreadingPass::duplicateCondBranchOnPHIIntoPred(
// Remap debug variable operands.
remapDebugVariable(ValueMapping, New);
if (const DebugLoc &DL = New->getDebugLoc())
mapAtomInstance(DL, ValueMapping);
// If this instruction can be simplified after the operands are updated,
// just use the simplified value instead. This frequently happens due to
@ -2740,6 +2745,10 @@ bool JumpThreadingPass::duplicateCondBranchOnPHIIntoPred(
addPHINodeEntriesForMappedBlock(BBBranch->getSuccessor(1), BB, PredBB,
ValueMapping);
// KeyInstructions: Remap the cloned instructions' atoms only.
remapSourceAtoms(ValueMapping, std::prev(RItBeforeInsertPt)->getIterator(),
OldPredBranch->getIterator());
updateSSA(BB, PredBB, ValueMapping);
// PredBB no longer jumps to BB, remove entries in the PHI node for the edge

87
llvm/test/DebugInfo/KeyInstructions/Generic/jump-threading-dup-cond-br-on-phi-into-pred.ll Normal file
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@ -0,0 +1,87 @@
; RUN: opt %s --passes=jump-threading -S -o - -S | FileCheck %s
;; +-> T1 -+
;; | v +-> T2
;; Entry -+ Merge -+
;; | ^ +-> F2
;; +-> F1 -+
;;
;; Duplicate Merge into T1 then fold Merge into its only pred F1 (taking its name).
;;
;; +-> T1 -----> T2
;; | \ ^
;; | \ /
;; | \ /
;; Entry -+ +----+
;; | / v
;; +--> Merge -> F2
;;
;; Check the duplicated (into T1) instructions' atoms are remapped.
; CHECK: T1:
; CHECK-NEXT: %v1 = call i32 @f1()
; CHECK-NEXT: %cond3 = icmp eq i32 %v1, 412
; CHECK-NEXT: %C1 = add i32 %v1, 1, !dbg [[G3R2:!.*]]
; CHECK-NEXT: store i32 %C1, ptr %p, align 4, !dbg [[G3R1:!.*]]
; CHECK: Merge:
; CHECK-NEXT: %v2 = call i32 @f2()
; CHECK-NEXT: store i32 1, ptr %p, align 4, !dbg [[G1R1:!.*]]
; CHECK-NEXT: %C = add i32 %v2, 1, !dbg [[G2R2:!.*]]
; CHECK-NEXT: store i32 %C, ptr %p, align 4, !dbg [[G2R1:!.*]]
; CHECK: [[G3R2]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 2)
; CHECK: [[G3R1]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 1)
; CHECK: [[G1R1]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 1)
; CHECK: [[G2R2]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 2)
; CHECK: [[G2R1]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 1)
define i32 @test5(i1 %cond, i1 %cond2, ptr %p) !dbg !5 {
br i1 %cond, label %T1, label %F1
T1: ; preds = %0
%v1 = call i32 @f1()
%cond3 = icmp eq i32 %v1, 412
br label %Merge
F1: ; preds = %0
%v2 = call i32 @f2()
store i32 1, ptr %p, align 4, !dbg !8
br label %Merge
Merge: ; preds = %F1, %T1
%A = phi i1 [ %cond3, %T1 ], [ %cond2, %F1 ]
%B = phi i32 [ %v1, %T1 ], [ %v2, %F1 ]
%C = add i32 %B, 1, !dbg !9
store i32 %C, ptr %p, align 4, !dbg !10
br i1 %A, label %T2, label %F2
T2: ; preds = %Merge
call void @f3()
ret i32 %B
F2: ; preds = %Merge
ret i32 %B
}
declare i32 @f1()
declare i32 @f2()
declare void @f3()
!llvm.dbg.cu = !{!0}
!llvm.debugify = !{!2, !3}
!llvm.module.flags = !{!4}
!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
!1 = !DIFile(filename: "test.ll", directory: "/")
!2 = !{i32 12}
!3 = !{i32 0}
!4 = !{i32 2, !"Debug Info Version", i32 3}
!5 = distinct !DISubprogram(name: "test5", linkageName: "test5", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
!6 = !DISubroutineType(types: !7)
!7 = !{}
!8 = !DILocation(line: 1, column: 1, scope: !5, atomGroup: 1, atomRank: 1)
!9 = !DILocation(line: 2, column: 1, scope: !5, atomGroup: 2, atomRank: 2)
!10 = !DILocation(line: 2, column: 1, scope: !5, atomGroup: 2, atomRank: 1)