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[JumpThreading] Avoid threadThroughTwoBasicBlocks when PredPred BB ends with indirectbranch 

Since we can't change the destination of indirectbr, so when
encounter indirectbr as PredPredBB terminator, we should pass it.

Differential Revision: https://reviews.llvm.org/D129193
This commit is contained in:
ChenYang Li 2022-07-08 09:29:17 +02:00 committed by Nikita Popov
parent 116c29a386
commit 6d036b83d1
2 changed files with 57 additions and 0 deletions
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3
llvm/lib/Transforms/Scalar/JumpThreading.cpp
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@ -2169,6 +2169,9 @@ bool JumpThreadingPass::maybethreadThroughTwoBasicBlocks(BasicBlock *BB,
BasicBlock *ZeroPred = nullptr;
BasicBlock *OnePred = nullptr;
for (BasicBlock *P : predecessors(PredBB)) {
// If PredPred ends with IndirectBrInst, we can't handle it.
if (isa<IndirectBrInst>(P->getTerminator()))
continue;
if (ConstantInt *CI = dyn_cast_or_null<ConstantInt>(
evaluateOnPredecessorEdge(BB, P, Cond))) {
if (CI->isZero()) {

54
llvm/test/Transforms/JumpThreading/indirectbr-in-predpred.ll Normal file
View File

@ -0,0 +1,54 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S < %s -jump-threading | FileCheck %s
define i1 @test1(i32 %0) #0 {
; CHECK-LABEL: @test1(
; CHECK-NEXT: PredPredBB1:
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 [[TMP0:%.*]], 0
; CHECK-NEXT: [[TMP1:%.*]] = add i32 32, [[TMP0]]
; CHECK-NEXT: [[INDIRECT_GOTO_DEST:%.*]] = select i1 [[CMP]], i8* blockaddress(@test1, [[PREDBB1:%.*]]), i8* blockaddress(@test1, [[PREDPREDBB2:%.*]])
; CHECK-NEXT: indirectbr i8* [[INDIRECT_GOTO_DEST]], [label [[PREDBB1]], label %PredPredBB2]
; CHECK: PredPredBB2:
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne i32 [[TMP0]], 1
; CHECK-NEXT: br i1 [[CMP1]], label [[PREDBB1]], label [[BB2:%.*]]
; CHECK: PredBB1:
; CHECK-NEXT: [[NUM:%.*]] = phi i32 [ 0, [[PREDPREDBB1:%.*]] ], [ [[TMP1]], [[PREDPREDBB2]] ]
; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[TMP1]], 100
; CHECK-NEXT: br i1 [[CMP2]], label [[BB1:%.*]], label [[BB2]]
; CHECK: BB1:
; CHECK-NEXT: [[CMP3:%.*]] = icmp eq i32 [[NUM]], 0
; CHECK-NEXT: br i1 [[CMP3]], label [[BB2]], label [[BB3:%.*]]
; CHECK: BB2:
; CHECK-NEXT: [[TMP2:%.*]] = or i1 [[CMP]], true
; CHECK-NEXT: ret i1 [[TMP2]]
; CHECK: BB3:
; CHECK-NEXT: ret i1 true
;
PredPredBB1:
%cmp = icmp ne i32 %0, 0
%1 = add i32 32, %0
%indirect.goto.dest = select i1 %cmp, i8* blockaddress(@test1, %PredBB1), i8* blockaddress(@test1, %PredPredBB2)
indirectbr i8* %indirect.goto.dest, [label %PredBB1, label %PredPredBB2]
PredPredBB2: ; preds = %PredPredBB1
%cmp1 = icmp ne i32 %0, 1
br i1 %cmp1, label %PredBB1, label %BB2
PredBB1: ; preds = %PredPredBB2, %PredPredBB1
%num = phi i32 [ 0, %PredPredBB1 ], [ %1, %PredPredBB2 ]
%cmp2 = icmp eq i32 %1, 100
br i1 %cmp2, label %BB1, label %BB2
BB1: ; preds = %PredBB1
%cmp3 = icmp eq i32 %num, 0
br i1 %cmp3, label %BB2, label %BB3
BB2: ; preds = %BB1, %PredBB1, %PredPredBB2
%2 = or i1 %cmp, true
ret i1 %2
BB3: ; preds = %BB1
ret i1 true
}
attributes #0 = { nounwind }