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It's easy to handle SLE/SGE when the loop has a unit stride.

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llvm-svn: 60748
This commit is contained in:
Nick Lewycky 2008-12-09 07:25:04 +00:00
parent 7358482dbc
commit 41060b1556
2 changed files with 29 additions and 1 deletions
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6
lib/Analysis/ScalarEvolution.cpp
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@ -2924,8 +2924,12 @@ bool ScalarEvolutionsImpl::potentialInfiniteLoop(SCEV *Stride, SCEV *RHS,
if (!R)
return true;
if (isSigned)
if (isSigned) {
if (SC->getValue()->isOne())
return R->getValue()->isMaxValue(true);
return true; // XXX: because we don't have an sdiv scev.
}
// If negative, it wraps around every iteration, but we don't care about that.
APInt S = SC->getValue()->getValue().abs();

24
test/Analysis/ScalarEvolution/2008-12-08-FiniteSGE.ll Normal file
View File

@ -0,0 +1,24 @@
; RUN: llvm-as < %s | opt -analyze -scalar-evolution | grep {255 iterations}
define i32 @foo(i32 %x, i32 %y, i32* %lam, i32* %alp) nounwind {
bb1.thread:
br label %bb1
bb1: ; preds = %bb1, %bb1.thread
%indvar = phi i32 [ 0, %bb1.thread ], [ %indvar.next, %bb1 ] ; <i32> [#uses=4]
%i.0.reg2mem.0 = sub i32 255, %indvar ; <i32> [#uses=2]
%0 = getelementptr i32* %alp, i32 %i.0.reg2mem.0 ; <i32*> [#uses=1]
%1 = load i32* %0, align 4 ; <i32> [#uses=1]
%2 = getelementptr i32* %lam, i32 %i.0.reg2mem.0 ; <i32*> [#uses=1]
store i32 %1, i32* %2, align 4
%3 = sub i32 254, %indvar ; <i32> [#uses=1]
%4 = icmp slt i32 %3, 0 ; <i1> [#uses=1]
%indvar.next = add i32 %indvar, 1 ; <i32> [#uses=1]
br i1 %4, label %bb2, label %bb1
bb2: ; preds = %bb1
%tmp10 = mul i32 %indvar, %x ; <i32> [#uses=1]
%z.0.reg2mem.0 = add i32 %tmp10, %y ; <i32> [#uses=1]
%5 = add i32 %z.0.reg2mem.0, %x ; <i32> [#uses=1]
ret i32 %5
}