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[JumpThreading] Add a basic support for freeze instruction
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This patch adds a basic support for freeze instruction to JumpThreading
by making ComputeValueKnownInPredecessorsImpl look into its operand.

Reviewed By: efriedma, nikic

Differential Revision: https://reviews.llvm.org/D84598
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@aqjune
aqjune committed Jul 28, 2020
1 parent 745eb02 commit 4c9af6d
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Showing 2 changed files with 60 additions and 64 deletions.
21 changes: 19 additions & 2 deletions llvm/lib/Transforms/Scalar/JumpThreading.cpp
View file
Expand Up @@ -675,10 +675,11 @@ bool JumpThreadingPass::ComputeValueKnownInPredecessorsImpl(
}

// Handle Cast instructions. Only see through Cast when the source operand is
// PHI or Cmp to save the compilation time.
// PHI, Cmp, or Freeze to save the compilation time.
if (CastInst *CI = dyn_cast<CastInst>(I)) {
Value *Source = CI->getOperand(0);
if (!isa<PHINode>(Source) && !isa<CmpInst>(Source))
if (!isa<PHINode>(Source) && !isa<CmpInst>(Source) &&
!isa<FreezeInst>(Source))
return false;
ComputeValueKnownInPredecessorsImpl(Source, BB, Result, Preference,
RecursionSet, CxtI);
Expand All @@ -692,6 +693,22 @@ 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);

erase_if(Result, [](auto &Pair) {
return !isGuaranteedNotToBeUndefOrPoison(Pair.first);
});

return !Result.empty();
}

// Handle some boolean conditions.
if (I->getType()->getPrimitiveSizeInBits() == 1) {
assert(Preference == WantInteger && "One-bit non-integer type?");
Expand Down
103 changes: 41 additions & 62 deletions llvm/test/Transforms/JumpThreading/freeze.ll
View file
Expand Up @@ -7,23 +7,14 @@ declare void @f3()

define i32 @test1(i1 %cond) {
; CHECK-LABEL: @test1(
; CHECK-NEXT: br i1 [[COND:%.*]], label [[T1:%.*]], label [[F1:%.*]]
; CHECK: T1:
; CHECK-NEXT: [[V1:%.*]] = call i32 @f1()
; CHECK-NEXT: br label [[MERGE:%.*]]
; CHECK: F1:
; CHECK-NEXT: [[V2:%.*]] = call i32 @f2()
; CHECK-NEXT: br label [[MERGE]]
; CHECK: Merge:
; CHECK-NEXT: [[A:%.*]] = phi i1 [ true, [[T1]] ], [ false, [[F1]] ]
; CHECK-NEXT: [[B:%.*]] = phi i32 [ [[V1]], [[T1]] ], [ [[V2]], [[F1]] ]
; CHECK-NEXT: [[A_FR:%.*]] = freeze i1 [[A]]
; CHECK-NEXT: br i1 [[A_FR]], label [[T2:%.*]], label [[F2:%.*]]
; CHECK-NEXT: br i1 [[COND:%.*]], label [[T2:%.*]], label [[F2:%.*]]
; CHECK: T2:
; CHECK-NEXT: [[V1:%.*]] = call i32 @f1()
; CHECK-NEXT: call void @f3()
; CHECK-NEXT: ret i32 [[B]]
; CHECK-NEXT: ret i32 [[V1]]
; CHECK: F2:
; CHECK-NEXT: ret i32 [[B]]
; CHECK-NEXT: [[V2:%.*]] = call i32 @f2()
; CHECK-NEXT: ret i32 [[V2]]
;
br i1 %cond, label %T1, label %F1

Expand Down Expand Up @@ -51,24 +42,21 @@ F2:

define i32 @test1_cast(i1 %cond) {
; CHECK-LABEL: @test1_cast(
; CHECK-NEXT: br i1 [[COND:%.*]], label [[T1:%.*]], label [[F1:%.*]]
; CHECK: T1:
; CHECK-NEXT: br i1 [[COND:%.*]], label [[MERGE_THREAD:%.*]], label [[MERGE:%.*]]
; CHECK: Merge.thread:
; CHECK-NEXT: [[V1:%.*]] = call i32 @f1()
; CHECK-NEXT: br label [[MERGE:%.*]]
; CHECK: F1:
; CHECK-NEXT: [[V2:%.*]] = call i32 @f2()
; CHECK-NEXT: br label [[MERGE]]
; CHECK-NEXT: br label [[T2:%.*]]
; CHECK: Merge:
; CHECK-NEXT: [[A0:%.*]] = phi i32 [ 1, [[T1]] ], [ 0, [[F1]] ]
; CHECK-NEXT: [[B:%.*]] = phi i32 [ [[V1]], [[T1]] ], [ [[V2]], [[F1]] ]
; CHECK-NEXT: [[A:%.*]] = trunc i32 [[A0]] to i1
; CHECK-NEXT: [[V2:%.*]] = call i32 @f2()
; CHECK-NEXT: [[A:%.*]] = trunc i32 0 to i1
; CHECK-NEXT: [[A_FR:%.*]] = freeze i1 [[A]]
; CHECK-NEXT: br i1 [[A_FR]], label [[T2:%.*]], label [[F2:%.*]]
; 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 [[B]]
; CHECK-NEXT: ret i32 [[B5]]
; CHECK: F2:
; CHECK-NEXT: ret i32 [[B]]
; CHECK-NEXT: ret i32 [[V2]]
;
br i1 %cond, label %T1, label %F1

Expand Down Expand Up @@ -97,24 +85,21 @@ F2:

define i32 @test1_cast2(i1 %cond) {
; CHECK-LABEL: @test1_cast2(
; CHECK-NEXT: br i1 [[COND:%.*]], label [[T1:%.*]], label [[F1:%.*]]
; CHECK: T1:
; CHECK-NEXT: br i1 [[COND:%.*]], label [[MERGE_THREAD:%.*]], label [[MERGE:%.*]]
; CHECK: Merge.thread:
; CHECK-NEXT: [[V1:%.*]] = call i32 @f1()
; CHECK-NEXT: br label [[MERGE:%.*]]
; CHECK: F1:
; CHECK-NEXT: [[V2:%.*]] = call i32 @f2()
; CHECK-NEXT: br label [[MERGE]]
; CHECK-NEXT: br label [[T2:%.*]]
; CHECK: Merge:
; CHECK-NEXT: [[A0:%.*]] = phi i32 [ 1, [[T1]] ], [ 0, [[F1]] ]
; CHECK-NEXT: [[B:%.*]] = phi i32 [ [[V1]], [[T1]] ], [ [[V2]], [[F1]] ]
; CHECK-NEXT: [[A0_FR:%.*]] = freeze i32 [[A0]]
; 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-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 [[B]]
; CHECK-NEXT: ret i32 [[B5]]
; CHECK: F2:
; CHECK-NEXT: ret i32 [[B]]
; CHECK-NEXT: ret i32 [[V2]]
;
br i1 %cond, label %T1, label %F1

Expand Down Expand Up @@ -143,23 +128,20 @@ F2:

define i32 @test1_undef(i1 %cond) {
; CHECK-LABEL: @test1_undef(
; CHECK-NEXT: br i1 [[COND:%.*]], label [[T1:%.*]], label [[F1:%.*]]
; CHECK: T1:
; CHECK-NEXT: br i1 [[COND:%.*]], label [[MERGE_THREAD:%.*]], label [[MERGE:%.*]]
; CHECK: Merge.thread:
; CHECK-NEXT: [[V1:%.*]] = call i32 @f1()
; CHECK-NEXT: br label [[MERGE:%.*]]
; CHECK: F1:
; CHECK-NEXT: [[V2:%.*]] = call i32 @f2()
; CHECK-NEXT: br label [[MERGE]]
; CHECK-NEXT: br label [[T2:%.*]]
; CHECK: Merge:
; CHECK-NEXT: [[A:%.*]] = phi i1 [ true, [[T1]] ], [ undef, [[F1]] ]
; CHECK-NEXT: [[B:%.*]] = phi i32 [ [[V1]], [[T1]] ], [ [[V2]], [[F1]] ]
; CHECK-NEXT: [[A_FR:%.*]] = freeze i1 [[A]]
; CHECK-NEXT: br i1 [[A_FR]], label [[T2:%.*]], label [[F2:%.*]]
; CHECK-NEXT: [[V2:%.*]] = call i32 @f2()
; CHECK-NEXT: [[A_FR:%.*]] = freeze i1 undef
; CHECK-NEXT: br i1 [[A_FR]], label [[T2]], label [[F2:%.*]]
; CHECK: T2:
; CHECK-NEXT: [[B4:%.*]] = phi i32 [ [[V1]], [[MERGE_THREAD]] ], [ [[V2]], [[MERGE]] ]
; CHECK-NEXT: call void @f3()
; CHECK-NEXT: ret i32 [[B]]
; CHECK-NEXT: ret i32 [[B4]]
; CHECK: F2:
; CHECK-NEXT: ret i32 [[B]]
; CHECK-NEXT: ret i32 [[V2]]
;
br i1 %cond, label %T1, label %F1

Expand Down Expand Up @@ -187,23 +169,20 @@ F2:

define i32 @test2(i1 %cond, i1 %cond2) {
; CHECK-LABEL: @test2(
; CHECK-NEXT: br i1 [[COND:%.*]], label [[T1:%.*]], label [[F1:%.*]]
; CHECK: T1:
; CHECK-NEXT: br i1 [[COND:%.*]], label [[MERGE_THREAD:%.*]], label [[MERGE:%.*]]
; CHECK: Merge.thread:
; CHECK-NEXT: [[V1:%.*]] = call i32 @f1()
; CHECK-NEXT: br label [[MERGE:%.*]]
; CHECK: F1:
; CHECK-NEXT: [[V2:%.*]] = call i32 @f2()
; CHECK-NEXT: br label [[MERGE]]
; CHECK-NEXT: br label [[T2:%.*]]
; CHECK: Merge:
; CHECK-NEXT: [[A:%.*]] = phi i1 [ true, [[T1]] ], [ [[COND2:%.*]], [[F1]] ]
; CHECK-NEXT: [[B:%.*]] = phi i32 [ [[V1]], [[T1]] ], [ [[V2]], [[F1]] ]
; CHECK-NEXT: [[A_FR:%.*]] = freeze i1 [[A]]
; CHECK-NEXT: br i1 [[A_FR]], label [[T2:%.*]], label [[F2:%.*]]
; CHECK-NEXT: [[V2:%.*]] = call i32 @f2()
; CHECK-NEXT: [[A_FR:%.*]] = freeze i1 [[COND2:%.*]]
; CHECK-NEXT: br i1 [[A_FR]], label [[T2]], label [[F2:%.*]]
; CHECK: T2:
; CHECK-NEXT: [[B4:%.*]] = phi i32 [ [[V1]], [[MERGE_THREAD]] ], [ [[V2]], [[MERGE]] ]
; CHECK-NEXT: call void @f3()
; CHECK-NEXT: ret i32 [[B]]
; CHECK-NEXT: ret i32 [[B4]]
; CHECK: F2:
; CHECK-NEXT: ret i32 [[B]]
; CHECK-NEXT: ret i32 [[V2]]
;
br i1 %cond, label %T1, label %F1

Expand Down

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