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[AMDGPU][UnifyLoopExits] Fix duplicate successor handling #170759

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Merged
shiltian merged 1 commit into from
Dec 8, 2025
Merged

[AMDGPU][UnifyLoopExits] Fix duplicate successor handling #170759

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8 changes: 5 additions & 3 deletions llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -755,9 +755,11 @@ BasicBlock *llvm::SplitCallBrEdge(BasicBlock *CallBrBlock, BasicBlock *Succ,
updateCycleLoopInfo<CycleInfo, Cycle>(CI, CallBrBlock, CallBrTarget, Succ);
if (DTU) {
DTU->applyUpdates({{DominatorTree::Insert, CallBrBlock, CallBrTarget}});
if (DTU->getDomTree().dominates(CallBrBlock, Succ))
DTU->applyUpdates({{DominatorTree::Delete, CallBrBlock, Succ},
{DominatorTree::Insert, CallBrTarget, Succ}});
if (DTU->getDomTree().dominates(CallBrBlock, Succ)) {
if (!is_contained(successors(CallBrBlock), Succ))
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@arsenm arsenm Dec 8, 2025

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I thought DomTree updater handled this for you?

DTU->applyUpdates({{DominatorTree::Delete, CallBrBlock, Succ}});
DTU->applyUpdates({{DominatorTree::Insert, CallBrTarget, Succ}});
}
}

return CallBrTarget;
Expand Down
43 changes: 35 additions & 8 deletions llvm/test/Transforms/UnifyLoopExits/basic.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -61,13 +61,13 @@ define void @loop_1_callbr(i1 %PredEntry, i1 %PredB, i1 %PredC, i1 %PredD) {
; CHECK-NEXT: br label [[B:%.*]]
; CHECK: B:
; CHECK-NEXT: callbr void asm "", "r,!i"(i1 [[PREDB:%.*]])
; CHECK-NEXT: to label [[C:%.*]] [label %B.target.E]
; CHECK-NEXT: to label [[C:%.*]] [label [[B_TARGET_E:%.*]]]
; CHECK: C:
; CHECK-NEXT: callbr void asm "", "r,!i"(i1 [[PREDC:%.*]])
; CHECK-NEXT: to label [[D:%.*]] [label %C.target.F]
; CHECK-NEXT: to label [[D:%.*]] [label [[C_TARGET_F:%.*]]]
; CHECK: D:
; CHECK-NEXT: callbr void asm "", "r,!i"(i1 [[PREDD:%.*]])
; CHECK-NEXT: to label [[A]] [label %D.target.F]
; CHECK-NEXT: to label [[A]] [label [[D_TARGET_F:%.*]]]
; CHECK: E:
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: F:
Expand All @@ -83,7 +83,7 @@ define void @loop_1_callbr(i1 %PredEntry, i1 %PredB, i1 %PredC, i1 %PredD) {
; CHECK: D.target.F:
; CHECK-NEXT: br label [[LOOP_EXIT_GUARD]]
; CHECK: loop.exit.guard:
; CHECK-NEXT: [[GUARD_X:%.*]] = phi i1 [ true, [[B_TARGET_E:%.*]] ], [ false, [[C_TARGET_F:%.*]] ], [ false, [[D_TARGET_F:%.*]] ]
; CHECK-NEXT: [[GUARD_X:%.*]] = phi i1 [ true, [[B_TARGET_E]] ], [ false, [[C_TARGET_F]] ], [ false, [[D_TARGET_F]] ]
; CHECK-NEXT: br i1 [[GUARD_X]], label [[X:%.*]], label [[Y]]
;
entry:
Expand Down Expand Up @@ -175,13 +175,13 @@ define void @loop_2_callbr(i1 %PredA, i1 %PredB, i1 %PredC) {
; CHECK-NEXT: br label [[A:%.*]]
; CHECK: A:
; CHECK-NEXT: callbr void asm "", "r,!i"(i1 [[PREDA:%.*]])
; CHECK-NEXT: to label [[B:%.*]] [label %A.target.X]
; CHECK-NEXT: to label [[B:%.*]] [label [[A_TARGET_X:%.*]]]
; CHECK: B:
; CHECK-NEXT: callbr void asm "", "r,!i"(i1 [[PREDB:%.*]])
; CHECK-NEXT: to label [[C:%.*]] [label %B.target.Y]
; CHECK-NEXT: to label [[C:%.*]] [label [[B_TARGET_Y:%.*]]]
; CHECK: C:
; CHECK-NEXT: callbr void asm "", "r,!i"(i1 [[PREDC:%.*]])
; CHECK-NEXT: to label [[D:%.*]] [label %C.target.Z]
; CHECK-NEXT: to label [[D:%.*]] [label [[C_TARGET_Z:%.*]]]
; CHECK: D:
; CHECK-NEXT: br label [[A]]
; CHECK: X:
Expand All @@ -199,7 +199,7 @@ define void @loop_2_callbr(i1 %PredA, i1 %PredB, i1 %PredC) {
; CHECK: C.target.Z:
; CHECK-NEXT: br label [[LOOP_EXIT_GUARD]]
; CHECK: loop.exit.guard:
; CHECK-NEXT: [[GUARD_X:%.*]] = phi i1 [ true, [[A_TARGET_X:%.*]] ], [ false, [[B_TARGET_Y:%.*]] ], [ false, [[C_TARGET_Z:%.*]] ]
; CHECK-NEXT: [[GUARD_X:%.*]] = phi i1 [ true, [[A_TARGET_X]] ], [ false, [[B_TARGET_Y]] ], [ false, [[C_TARGET_Z]] ]
; CHECK-NEXT: [[GUARD_Y:%.*]] = phi i1 [ false, [[A_TARGET_X]] ], [ true, [[B_TARGET_Y]] ], [ false, [[C_TARGET_Z]] ]
; CHECK-NEXT: br i1 [[GUARD_X]], label [[X:%.*]], label [[LOOP_EXIT_GUARD1:%.*]]
; CHECK: loop.exit.guard1:
Expand Down Expand Up @@ -232,3 +232,30 @@ Z:
exit:
ret void
}

; Test that UnifyLoopExits handles callbr with duplicate successors correctly.
; The exit block appears twice as a successor of the callbr instruction.
define void @callbr_duplicate_successors() {
; CHECK-LABEL: @callbr_duplicate_successors(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: callbr void asm sideeffect "", "!i,!i"()
; CHECK-NEXT: to label [[LOOP_TARGET_EXIT:%.*]] [label [[LOOP]], label [[LOOP_TARGET_EXIT1:%.*]]]
; CHECK: exit:
; CHECK-NEXT: ret void
; CHECK: loop.target.exit:
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: loop.target.exit1:
; CHECK-NEXT: br label [[EXIT]]
;
entry:
br label %loop

loop:
callbr void asm sideeffect "", "!i,!i"()
to label %exit [label %loop, label %exit]

exit:
ret void
}
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