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9d55b40815
Summary:
This implements a new method of run-time checking the NoWrap
SCEV predicates, which should be easier to optimize and nicer
for targets that don't correctly handle multiplication/addition
of large integer types (like i128).
If the AddRec is {a,+,b} and the backedge taken count is c,
the idea is to check that |b| * c doesn't have unsigned overflow,
and depending on the sign of b, that:
a + |b| * c >= a (b >= 0) or
a - |b| * c <= a (b <= 0)
where the comparisons above are signed or unsigned, depending on
the flag that we're checking.
The advantage of doing this is that we avoid extending to a larger
type and we avoid the multiplication of large types (multiplying
i128 can be expensive).
Reviewers: sanjoy
Subscribers: llvm-commits, mzolotukhin
Differential Revision: http://reviews.llvm.org/D19266
llvm-svn: 267389
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| .. | ||
| backward-dep-different-types.ll | ||
| forward-loop-carried.ll | ||
| forward-loop-independent.ll | ||
| interleave-innermost.ll | ||
| memcheck-for-loop-invariant.ll | ||
| non-wrapping-pointer.ll | ||
| nullptr.ll | ||
| number-of-memchecks.ll | ||
| pointer-with-unknown-bounds.ll | ||
| resort-to-memchecks-only.ll | ||
| reverse-memcheck-bounds.ll | ||
| safe-no-checks.ll | ||
| store-to-invariant-check1.ll | ||
| store-to-invariant-check2.ll | ||
| store-to-invariant-check3.ll | ||
| stride-access-dependence.ll | ||
| underlying-objects-1.ll | ||
| underlying-objects-2.ll | ||
| unsafe-and-rt-checks.ll | ||
| wrapping-pointer-versioning.ll | ||