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[JumpThreading] Don't limit the type of an operand

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Compared to the optimized code with branch conditions never frozen,
limiting the type of freeze's operand causes generation of suboptimal code in
some cases.
I would like to suggest removing the constraint, as this patch does.
If the number of freeze instructions becomes significant, this can be revisited.

Differential Revision: https://reviews.llvm.org/D84949
This commit is contained in:
Juneyoung Lee 2020-07-30 23:46:26 +09:00
parent bbcdb3cf6d
commit aea992fbc0
2 changed files with 5 additions and 15 deletions
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4
lib/Transforms/Scalar/JumpThreading.cpp
View File

@ -693,12 +693,8 @@ bool JumpThreadingPass::ComputeValueKnownInPredecessorsImpl(
return true;
}
// Handle Freeze instructions, in a manner similar to Cast.
if (FreezeInst *FI = dyn_cast<FreezeInst>(I)) {
Value *Source = FI->getOperand(0);
if (!isa<PHINode>(Source) && !isa<CmpInst>(Source) &&
!isa<CastInst>(Source))
return false;
ComputeValueKnownInPredecessorsImpl(Source, BB, Result, Preference,
RecursionSet, CxtI);

16
test/Transforms/JumpThreading/freeze.ll
View File

@ -85,20 +85,14 @@ F2:
define i32 @test1_cast2(i1 %cond) {
; CHECK-LABEL: @test1_cast2(
; CHECK-NEXT: br i1 [[COND:%.*]], label [[MERGE_THREAD:%.*]], label [[MERGE:%.*]]
; CHECK: Merge.thread:
; CHECK-NEXT: br i1 [[COND:%.*]], label [[T2:%.*]], label [[F2:%.*]]
; CHECK: T2:
; CHECK-NEXT: [[V1:%.*]] = call i32 @f1()
; CHECK-NEXT: br label [[T2:%.*]]
; CHECK: Merge:
; CHECK-NEXT: call void @f3()
; CHECK-NEXT: ret i32 [[V1]]
; CHECK: F2:
; CHECK-NEXT: [[V2:%.*]] = call i32 @f2()
; CHECK-NEXT: [[A0_FR:%.*]] = freeze i32 0
; CHECK-NEXT: [[A_FR:%.*]] = trunc i32 [[A0_FR]] to i1
; CHECK-NEXT: br i1 [[A_FR]], label [[T2]], label [[F2:%.*]]
; CHECK: T2:
; CHECK-NEXT: [[B5:%.*]] = phi i32 [ [[V1]], [[MERGE_THREAD]] ], [ [[V2]], [[MERGE]] ]
; CHECK-NEXT: call void @f3()
; CHECK-NEXT: ret i32 [[B5]]
; CHECK: F2:
; CHECK-NEXT: ret i32 [[V2]]
;
br i1 %cond, label %T1, label %F1