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Revert my re-instated reverted commit, fixes the bootstrap build on x86-64 linux.

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llvm-svn: 60951
This commit is contained in:
Nick Lewycky 2008-12-12 17:09:07 +00:00
parent 06ecf57a87
commit 51228d6707
3 changed files with 17 additions and 15 deletions
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30
lib/Analysis/ScalarEvolution.cpp
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@ -2924,12 +2924,8 @@ bool ScalarEvolutionsImpl::potentialInfiniteLoop(SCEV *Stride, SCEV *RHS,
if (!R) if (!R)
return true; 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. 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. // If negative, it wraps around every iteration, but we don't care about that.
APInt S = SC->getValue()->getValue().abs(); APInt S = SC->getValue()->getValue().abs();
@ -2975,6 +2971,14 @@ HowManyLessThans(SCEV *LHS, SCEV *RHS, const Loop *L,
// run (m-n)/s times. // run (m-n)/s times.
SCEVHandle End = RHS; SCEVHandle End = RHS;
if (!executesAtLeastOnce(L, isSigned, trueWhenEqual,
SE.getMinusSCEV(Start, One), RHS)) {
// If not, we get the value of the LHS in the first iteration in which
// the above condition doesn't hold. This equals to max(m,n).
End = isSigned ? SE.getSMaxExpr(RHS, Start)
: SE.getUMaxExpr(RHS, Start);
}
// If the expression is less-than-or-equal to, we need to extend the // If the expression is less-than-or-equal to, we need to extend the
// loop by one iteration. // loop by one iteration.
// //
@ -2983,16 +2987,12 @@ HowManyLessThans(SCEV *LHS, SCEV *RHS, const Loop *L,
// division would equal one, but the loop runs twice putting the // division would equal one, but the loop runs twice putting the
// induction variable at 12. // induction variable at 12.
if (trueWhenEqual) if (!trueWhenEqual)
End = SE.getAddExpr(End, One); // (Stride - 1) is correct only because we know it's unsigned.
// What we really want is to decrease the magnitude of Stride by one.
if (!executesAtLeastOnce(L, isSigned, trueWhenEqual, Start = SE.getMinusSCEV(Start, SE.getMinusSCEV(Stride, One));
SE.getMinusSCEV(Start, One), RHS)) { else
// If not, we get the value of the LHS in the first iteration in which Start = SE.getMinusSCEV(Start, Stride);
// the above condition doesn't hold. This equals to max(m,n).
End = isSigned ? SE.getSMaxExpr(End, Start)
: SE.getUMaxExpr(End, Start);
}
// Finally, we subtract these two values to get the number of times the // Finally, we subtract these two values to get the number of times the
// backedge is executed: max(m,n)-n. // backedge is executed: max(m,n)-n.

1
test/Analysis/ScalarEvolution/2008-12-08-FiniteSGE.ll
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@ -1,4 +1,5 @@
; RUN: llvm-as < %s | opt -analyze -scalar-evolution | grep {255 iterations} ; RUN: llvm-as < %s | opt -analyze -scalar-evolution | grep {255 iterations}
; XFAIL: *
define i32 @foo(i32 %x, i32 %y, i32* %lam, i32* %alp) nounwind { define i32 @foo(i32 %x, i32 %y, i32* %lam, i32* %alp) nounwind {
bb1.thread: bb1.thread:

1
test/Analysis/ScalarEvolution/2008-12-11-SMaxOverflow.ll
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@ -1,4 +1,5 @@
; RUN: llvm-as < %s | opt -analyze -scalar-evolution | grep {0 smax} ; RUN: llvm-as < %s | opt -analyze -scalar-evolution | grep {0 smax}
; XFAIL: *
define i32 @f(i32 %c.idx.val) { define i32 @f(i32 %c.idx.val) {