[PATCH] Exit ScalarEvolution::getMulExpr Early when Choose Overflows

[Nick Lewycky]

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Comment at: lib/Analysis/ScalarEvolution.cpp:2120
@@ -2094,3 +2119,3 @@
           const SCEV *Term = getConstant(Ty, 0);
           for (int y = x, ye = 2*x+1; y != ye && !Overflow; ++y) {
             uint64_t Coeff1 = Choose(x, 2*x - y, Overflow);
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You tested whether we'll overflow up front. Is that the exact case where we overflow or does it only catch some of the cases where we overflow? If it's exactly right, then we can stop updating and checking Overflow in here, right?

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Comment at: test/Analysis/ScalarEvolution/choose-overflow-fast.ll:1
@@ +1,2 @@
+; RUN: opt < %s -iv-users
+
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Can you use "opt < %s -analyze -scalar-evolution" instead?

http://reviews.llvm.org/D5113