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[SimplifyCFG] `FoldBranchToCommonDest()`: allow branch-on-select 

This whole check is bogus, it's some kind of a profitability check.
For now, simply extend it to not only allow branch-on-binary-ops,
but also on poison-safe logic ops.

Refs. https://github.com/llvm/llvm-project/issues/53861
Refs. https://github.com/llvm/llvm-project/issues/54553
This commit is contained in:
Roman Lebedev 2022-03-25 15:11:49 +03:00
parent ead294b74c
commit f6b60b3b79
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GPG Key ID: 083C3EBB4A1689E0
2 changed files with 6 additions and 10 deletions
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4
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -3531,7 +3531,9 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, DomTreeUpdater *DTU,
Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
if (!Cond || (!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) ||
if (!Cond ||
(!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond) &&
!isa<SelectInst>(Cond)) ||
Cond->getParent() != BB || !Cond->hasOneUse())
return false;

12
llvm/test/Transforms/SimplifyCFG/fold-branch-to-common-dest.ll
View File

@ -1074,22 +1074,16 @@ define i32 @firewall(i8* %data) {
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[I]], 17
; CHECK-NEXT: [[CMP3:%.*]] = icmp eq i16 [[I2]], 1
; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[CMP]], i1 [[CMP3]], i1 false
; CHECK-NEXT: br i1 [[OR_COND]], label [[CLEANUP:%.*]], label [[IF_END:%.*]]
; CHECK: if.end:
; CHECK-NEXT: [[CMP10:%.*]] = icmp eq i16 [[I2]], 2
; CHECK-NEXT: [[OR_COND33:%.*]] = select i1 [[CMP]], i1 [[CMP10]], i1 false
; CHECK-NEXT: br i1 [[OR_COND33]], label [[CLEANUP]], label [[IF_END13:%.*]]
; CHECK: if.end13:
; CHECK-NEXT: [[OR_COND1:%.*]] = select i1 [[OR_COND]], i1 true, i1 [[OR_COND33]]
; CHECK-NEXT: [[CMP19:%.*]] = icmp eq i16 [[I2]], 3
; CHECK-NEXT: [[OR_COND34:%.*]] = select i1 [[CMP]], i1 [[CMP19]], i1 false
; CHECK-NEXT: br i1 [[OR_COND34]], label [[CLEANUP]], label [[IF_END22:%.*]]
; CHECK: if.end22:
; CHECK-NEXT: [[OR_COND2:%.*]] = select i1 [[OR_COND1]], i1 true, i1 [[OR_COND34]]
; CHECK-NEXT: [[CMP28:%.*]] = icmp eq i16 [[I2]], 4
; CHECK-NEXT: [[OR_COND35:%.*]] = select i1 [[CMP]], i1 [[CMP28]], i1 false
; CHECK-NEXT: [[DOT:%.*]] = zext i1 [[OR_COND35]] to i32
; CHECK-NEXT: br label [[CLEANUP]]
; CHECK: cleanup:
; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i32 [ 1, [[ENTRY:%.*]] ], [ 1, [[IF_END]] ], [ 1, [[IF_END13]] ], [ [[DOT]], [[IF_END22]] ]
; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[OR_COND2]], i32 1, i32 [[DOT]]
; CHECK-NEXT: ret i32 [[RETVAL_0]]
;
entry: