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Allow scalar evolution to compute iteration counts for loops with a 

pointer-based condition.  This fixes PR3171.

llvm-svn: 71354
This commit is contained in:
Eli Friedman 2009-05-09 12:32:42 +00:00
parent e3e94bbf19
commit ebf98b0212
2 changed files with 34 additions and 18 deletions
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25
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -2372,10 +2372,8 @@ ScalarEvolution::ComputeBackedgeTakenCount(const Loop *L) {
ICmpInst *ExitCond = dyn_cast<ICmpInst>(ExitBr->getCondition());
// If it's not an integer comparison then compute it the hard way.
// Note that ICmpInst deals with pointer comparisons too so we must check
// the type of the operand.
if (ExitCond == 0 || isa<PointerType>(ExitCond->getOperand(0)->getType()))
// If it's not an integer or pointer comparison then compute it the hard way.
if (ExitCond == 0)
return ComputeBackedgeTakenCountExhaustively(L, ExitBr->getCondition(),
ExitBr->getSuccessor(0) == ExitBlock);
@ -2416,21 +2414,12 @@ ScalarEvolution::ComputeBackedgeTakenCount(const Loop *L) {
if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
if (AddRec->getLoop() == L) {
// Form the comparison range using the constant of the correct type so
// that the ConstantRange class knows to do a signed or unsigned
// comparison.
ConstantInt *CompVal = RHSC->getValue();
const Type *RealTy = ExitCond->getOperand(0)->getType();
CompVal = dyn_cast<ConstantInt>(
ConstantExpr::getBitCast(CompVal, RealTy));
if (CompVal) {
// Form the constant range.
ConstantRange CompRange(
ICmpInst::makeConstantRange(Cond, CompVal->getValue()));
// Form the constant range.
ConstantRange CompRange(
ICmpInst::makeConstantRange(Cond, RHSC->getValue()->getValue()));
SCEVHandle Ret = AddRec->getNumIterationsInRange(CompRange, *this);
if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
}
SCEVHandle Ret = AddRec->getNumIterationsInRange(CompRange, *this);
if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
}
switch (Cond) {

27
llvm/test/Analysis/ScalarEvolution/2009-05-09-PointerEdgeCount.ll Normal file
View File

@ -0,0 +1,27 @@
; RUN: llvm-as < %s | opt -analyze -scalar-evolution | grep {count is 2}
; PR3171
%struct.Foo = type { i32 }
%struct.NonPod = type { [2 x %struct.Foo] }
define void @_Z3foov() nounwind {
entry:
%x = alloca %struct.NonPod, align 8 ; <%struct.NonPod*> [#uses=2]
%0 = getelementptr %struct.NonPod* %x, i32 0, i32 0 ; <[2 x %struct.Foo]*> [#uses=1]
%1 = getelementptr [2 x %struct.Foo]* %0, i32 1, i32 0 ; <%struct.Foo*> [#uses=1]
br label %bb1.i
bb1.i: ; preds = %bb2.i, %entry
%.0.i = phi %struct.Foo* [ %1, %entry ], [ %4, %bb2.i ] ; <%struct.Foo*> [#uses=2]
%2 = getelementptr %struct.NonPod* %x, i32 0, i32 0, i32 0 ; <%struct.Foo*> [#uses=1]
%3 = icmp eq %struct.Foo* %.0.i, %2 ; <i1> [#uses=1]
br i1 %3, label %_ZN6NonPodD1Ev.exit, label %bb2.i
bb2.i: ; preds = %bb1.i
%4 = getelementptr %struct.Foo* %.0.i, i32 -1 ; <%struct.Foo*> [#uses=1]
br label %bb1.i
_ZN6NonPodD1Ev.exit: ; preds = %bb1.i
ret void
}