Teach IVUsers to stop at non-affine expressions unless they are both
outside the loop and reducible.
This more completely hides them from LSR, which isn't usually able to
do anything meaningful with non-affine expressions anyway, and this
consequently hides them from SCEVExpander, which is acutely unprepared
for non-affine expressions.
Replace test/CodeGen/X86/lsr-nonaffine.ll with a new test that tests
the new behavior.
This works around the bug in PR10117 / rdar://problem/9633149, and is
generally an improvement besides.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134268 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/IVUsers.cpp b/lib/Analysis/IVUsers.cpp
index 7a9dc0f..e5f0a77 100644
--- a/lib/Analysis/IVUsers.cpp
+++ b/lib/Analysis/IVUsers.cpp
@@ -46,17 +46,20 @@
/// 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,
- ScalarEvolution *SE) {
+ ScalarEvolution *SE, LoopInfo *LI) {
// 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.
+ // Keep things simple. Don't touch loop-variant strides unless they're
+ // only used outside the loop and we can simplify them.
if (AR->getLoop() == L)
- return AR->isAffine() || !L->contains(I);
+ return AR->isAffine() ||
+ (!L->contains(I) &&
+ SE->getSCEVAtScope(AR, LI->getLoopFor(I->getParent())) != AR);
// 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);
+ return isInteresting(AR->getStart(), I, L, SE, LI) &&
+ !isInteresting(AR->getStepRecurrence(*SE), I, L, SE, LI);
}
// An add is interesting if exactly one of its operands is interesting.
@@ -64,7 +67,7 @@
bool AnyInterestingYet = false;
for (SCEVAddExpr::op_iterator OI = Add->op_begin(), OE = Add->op_end();
OI != OE; ++OI)
- if (isInteresting(*OI, I, L, SE)) {
+ if (isInteresting(*OI, I, L, SE, LI)) {
if (AnyInterestingYet)
return false;
AnyInterestingYet = true;
@@ -98,7 +101,7 @@
// If we've come to an uninteresting expression, stop the traversal and
// call this a user.
- if (!isInteresting(ISE, I, L, SE))
+ if (!isInteresting(ISE, I, L, SE, LI))
return false;
SmallPtrSet<Instruction *, 4> UniqueUsers;