Sneaky, sneaky: move the -1 to the outside of the SMax. Reinstate the
optimization of SGE/SLE with unit stride, now that it works properly.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60881 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 2b714de..1dd5026 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -2924,8 +2924,12 @@
if (!R)
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.
+ }
// If negative, it wraps around every iteration, but we don't care about that.
APInt S = SC->getValue()->getValue().abs();
@@ -2971,14 +2975,6 @@
// run (m-n)/s times.
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
// loop by one iteration.
//
@@ -2987,12 +2983,16 @@
// division would equal one, but the loop runs twice putting the
// induction variable at 12.
- if (!trueWhenEqual)
- // (Stride - 1) is correct only because we know it's unsigned.
- // What we really want is to decrease the magnitude of Stride by one.
- Start = SE.getMinusSCEV(Start, SE.getMinusSCEV(Stride, One));
- else
- Start = SE.getMinusSCEV(Start, Stride);
+ if (trueWhenEqual)
+ End = SE.getAddExpr(End, One);
+
+ 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(End, Start)
+ : SE.getUMaxExpr(End, Start);
+ }
// Finally, we subtract these two values to get the number of times the
// backedge is executed: max(m,n)-n.