Tweak IVUsers' concept of "interesting" to exclude add recurrences
where the step value is an induction variable from an outer loop, to
avoid trouble trying to re-expand such expressions. This effectively
hides such expressions from indvars and lsr, which prevents them
from getting into trouble.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111317 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/IVUsers.cpp b/lib/Analysis/IVUsers.cpp
index bd43026..fd51433 100644
--- a/lib/Analysis/IVUsers.cpp
+++ b/lib/Analysis/IVUsers.cpp
@@ -38,27 +38,31 @@
/// isInteresting - Test whether the given expression is "interesting" when
/// used by the given expression, within the context of analyzing the
/// given loop.
-static bool isInteresting(const SCEV *S, const Instruction *I, const Loop *L) {
- // Anything loop-invariant is interesting.
- if (!isa<SCEVUnknown>(S) && S->isLoopInvariant(L))
- return true;
-
+static bool isInteresting(const SCEV *S, const Instruction *I, const Loop *L,
+ ScalarEvolution *SE) {
// An addrec is interesting if it's affine or if it has an interesting start.
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
// Keep things simple. Don't touch loop-variant strides.
if (AR->getLoop() == L)
return AR->isAffine() || !L->contains(I);
- // Otherwise recurse to see if the start value is interesting.
- return isInteresting(AR->getStart(), I, L);
+ // Otherwise recurse to see if the start value is interesting, and that
+ // the step value is not interesting, since we don't yet know how to
+ // do effective SCEV expansions for addrecs with interesting steps.
+ return isInteresting(AR->getStart(), I, L, SE) &&
+ !isInteresting(AR->getStepRecurrence(*SE), I, L, SE);
}
- // An add is interesting if any of its operands is.
+ // An add is interesting if exactly one of its operands is interesting.
if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
+ bool AnyInterestingYet = false;
for (SCEVAddExpr::op_iterator OI = Add->op_begin(), OE = Add->op_end();
OI != OE; ++OI)
- if (isInteresting(*OI, I, L))
- return true;
- return false;
+ if (isInteresting(*OI, I, L, SE)) {
+ if (AnyInterestingYet)
+ return false;
+ AnyInterestingYet = true;
+ }
+ return AnyInterestingYet;
}
// Nothing else is interesting here.
@@ -84,7 +88,7 @@
// If we've come to an uninteresting expression, stop the traversal and
// call this a user.
- if (!isInteresting(ISE, I, L))
+ if (!isInteresting(ISE, I, L, SE))
return false;
SmallPtrSet<Instruction *, 4> UniqueUsers;