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[LVI] Fix a bug with a guard being the very first instruction in a BB not taken into account 

While looking for guards use reverse iterator and scan up to rend() not to begin()

llvm-svn: 284827
This commit is contained in:
Artur Pilipenko 2016-10-21 15:02:21 +00:00
parent 501be9b3d7
commit 47dc098c06
2 changed files with 21 additions and 5 deletions
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7
llvm/lib/Analysis/LazyValueInfo.cpp
View File

@ -978,11 +978,10 @@ void LazyValueInfoImpl::intersectAssumeOrGuardBlockValueConstantRange(
if (!GuardDecl || GuardDecl->use_empty())
return;
for (BasicBlock::iterator I = BBI->getIterator(),
E = BBI->getParent()->begin(); I != E; I--) {
for (Instruction &I : make_range(BBI->getIterator().getReverse(),
BBI->getParent()->rend())) {
Value *Cond = nullptr;
if (!match(&*I, m_Intrinsic<Intrinsic::experimental_guard>(m_Value(Cond))))
continue;
if (match(&I, m_Intrinsic<Intrinsic::experimental_guard>(m_Value(Cond))))
BBLV = intersect(BBLV, getValueFromCondition(Val, Cond));
}
}

17
llvm/test/Transforms/CorrelatedValuePropagation/guards.ll
View File

@ -93,3 +93,20 @@ continue:
%result = or i1 %dead, %alive
ret i1 %result
}
; Check that we handle the case when the guard is the very first instruction in
; a basic block.
define i1 @test6(i32 %a) {
; CHECK-LABEL: @test6(
; CHECK: %alive = icmp eq i32 %a, 8
; CHECK-NEXT: %result = or i1 false, %alive
%cmp = icmp ult i32 %a, 16
br label %continue
continue:
call void(i1,...) @llvm.experimental.guard(i1 %cmp) [ "deopt"() ]
%dead = icmp eq i32 %a, 16
%alive = icmp eq i32 %a, 8
%result = or i1 %dead, %alive
ret i1 %result
}