indvars: generalize SCEV getPreStartForSignExtend.
Handle general Add expressions to avoid leaving around redundant
32-bit IVs.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140701 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index b1662a0..ea45e9d 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -1070,14 +1070,26 @@
// Check for a simple looking step prior to loop entry.
const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Start);
- if (!SA || SA->getNumOperands() != 2 || SA->getOperand(0) != Step)
+ if (!SA)
+ return 0;
+
+ // Create an AddExpr for "PreStart" after subtracting Step. Full SCEV
+ // subtraction is expensive. For this purpose, perform a quick and dirty
+ // difference, by checking for Step in the operand list.
+ SmallVector<const SCEV *, 4> DiffOps;
+ for (SCEVAddExpr::op_iterator I = SA->op_begin(), E = SA->op_end();
+ I != E; ++I) {
+ if (*I != Step)
+ DiffOps.push_back(*I);
+ }
+ if (DiffOps.size() == SA->getNumOperands())
return 0;
// This is a postinc AR. Check for overflow on the preinc recurrence using the
// same three conditions that getSignExtendedExpr checks.
// 1. NSW flags on the step increment.
- const SCEV *PreStart = SA->getOperand(1);
+ const SCEV *PreStart = SE->getAddExpr(DiffOps, SA->getNoWrapFlags());
const SCEVAddRecExpr *PreAR = dyn_cast<SCEVAddRecExpr>(
SE->getAddRecExpr(PreStart, Step, L, SCEV::FlagAnyWrap));