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[ValueTracking] Use guards to prove non-nullness of a value

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Reviewers: apilipenko, majnemer, reames

Subscribers: mcrosier, llvm-commits

Differential Revision: http://reviews.llvm.org/D20044

llvm-svn: 269008
This commit is contained in:
Sanjoy Das 2016-05-10 02:35:44 +00:00
parent cf2951e884
commit bbb7dedca9
2 changed files with 96 additions and 9 deletions
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20
lib/Analysis/ValueTracking.cpp
View File

@ -3212,17 +3212,19 @@ static bool isKnownNonNullFromDominatingCondition(const Value *V,
continue; continue;
for (auto *CmpU : U->users()) { for (auto *CmpU : U->users()) {
const BranchInst *BI = dyn_cast<BranchInst>(CmpU); if (const BranchInst *BI = dyn_cast<BranchInst>(CmpU)) {
if (!BI) assert(BI->isConditional() && "uses a comparison!");
continue;
assert(BI->isConditional() && "uses a comparison!"); BasicBlock *NonNullSuccessor =
BI->getSuccessor(Pred == ICmpInst::ICMP_EQ ? 1 : 0);
BasicBlock *NonNullSuccessor = BasicBlockEdge Edge(BI->getParent(), NonNullSuccessor);
BI->getSuccessor(Pred == ICmpInst::ICMP_EQ ? 1 : 0); if (Edge.isSingleEdge() && DT->dominates(Edge, CtxI->getParent()))
BasicBlockEdge Edge(BI->getParent(), NonNullSuccessor); return true;
if (Edge.isSingleEdge() && DT->dominates(Edge, CtxI->getParent())) } else if (Pred == ICmpInst::ICMP_NE &&
match(CmpU, m_Intrinsic<Intrinsic::experimental_guard>()) &&
DT->dominates(cast<Instruction>(CmpU), CtxI)) {
return true; return true;
}
} }
} }

85
test/Transforms/LICM/hoist-deref-load.ll
View File

@ -469,5 +469,90 @@ for.end: ; preds = %for.inc, %entry
ret void ret void
} }
declare void @llvm.experimental.guard(i1, ...)
define void @test12(i32* noalias %a, i32* %b, i32* dereferenceable_or_null(4) %c, i32 %n) #0 {
; Prove non-null ness of %c via a guard, not a branch.
; CHECK-LABEL: @test12(
entry:
%not_null = icmp ne i32* %c, null
call void(i1, ...) @llvm.experimental.guard(i1 %not_null) [ "deopt"() ]
%cmp11 = icmp sgt i32 %n, 0
br i1 %cmp11, label %for.body, label %for.end
; CHECK: for.body.preheader:
; CHECK-NEXT: [[VAL:%[^ ]]] = load i32, i32* %c, align 4
; CHECK-NEXT: br label %for.body
for.body: ; preds = %entry, %for.inc
%indvars.iv = phi i64 [ %indvars.iv.next, %for.inc ], [ 0, %entry ]
%arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
%0 = load i32, i32* %arrayidx, align 4
%cmp1 = icmp sgt i32 %0, 0
br i1 %cmp1, label %if.then, label %for.inc
if.then: ; preds = %for.body
%1 = load i32, i32* %c, align 4
%arrayidx3 = getelementptr inbounds i32, i32* %b, i64 %indvars.iv
%2 = load i32, i32* %arrayidx3, align 4
%mul = mul nsw i32 %2, %1
store i32 %mul, i32* %arrayidx, align 4
br label %for.inc
for.inc: ; preds = %for.body, %if.then
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%lftr.wideiv = trunc i64 %indvars.iv.next to i32
%exitcond = icmp eq i32 %lftr.wideiv, %n
br i1 %exitcond, label %for.end, label %for.body
for.end: ; preds = %for.inc, %entry, %entry
ret void
}
define void @test13(i32* noalias %a, i32* %b, i32* dereferenceable_or_null(4) %c, i32 %n) #0 {
; Like @test12, but has a post-dominating guard, which cannot be used
; to prove %c is nonnull at the point of the load.
; CHECK-LABEL: @test13(
entry:
%not_null = icmp ne i32* %c, null
%cmp11 = icmp sgt i32 %n, 0
br i1 %cmp11, label %for.body, label %for.end
; CHECK: for.body.preheader:
; CHECK-NOT: load i32, i32* %c
; CHECK: br label %for.body
for.body: ; preds = %entry, %for.inc
%indvars.iv = phi i64 [ %indvars.iv.next, %for.inc ], [ 0, %entry ]
%arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
%0 = load i32, i32* %arrayidx, align 4
%cmp1 = icmp sgt i32 %0, 0
br i1 %cmp1, label %if.then, label %for.inc
if.then: ; preds = %for.body
; CHECK: if.then:
; CHECK: load i32, i32* %c
; CHECK: br label %for.inc
%1 = load i32, i32* %c, align 4
%arrayidx3 = getelementptr inbounds i32, i32* %b, i64 %indvars.iv
%2 = load i32, i32* %arrayidx3, align 4
%mul = mul nsw i32 %2, %1
store i32 %mul, i32* %arrayidx, align 4
br label %for.inc
for.inc: ; preds = %for.body, %if.then
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%lftr.wideiv = trunc i64 %indvars.iv.next to i32
%exitcond = icmp eq i32 %lftr.wideiv, %n
br i1 %exitcond, label %for.end, label %for.body
for.end: ; preds = %for.inc, %entry, %entry
call void(i1, ...) @llvm.experimental.guard(i1 %not_null) [ "deopt"() ]
ret void
}
attributes #0 = { nounwind uwtable } attributes #0 = { nounwind uwtable }
!0 = !{i64 4} !0 = !{i64 4}