When complicated expressions are broken down into subexpressions
with multiplication by constants distributed through, occasionally
those subexpressions can include both x and -x. For now, if this
condition is discovered within LSR, just prune such cases away,
as they won't be profitable. This fixes a "zero allocated in a
base register" assertion failure.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96177 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index b6ef718..11f2187 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -2012,8 +2012,14 @@
F.BaseRegs.push_back(BaseReg);
}
if (Ops.size() > 1) {
- F.BaseRegs.push_back(SE.getAddExpr(Ops));
- (void)InsertFormula(LU, LUIdx, F);
+ const SCEV *Sum = SE.getAddExpr(Ops);
+ // TODO: If Sum is zero, it probably means ScalarEvolution missed an
+ // opportunity to fold something. For now, just ignore such cases
+ // rather than procede with zero in a register.
+ if (!Sum->isZero()) {
+ F.BaseRegs.push_back(Sum);
+ (void)InsertFormula(LU, LUIdx, F);
+ }
}
}