Oleg Ranevskyy 34bf60ca68 [SCEV] No-wrap flags are not propagated when folding "{S,+,X}+T ==> {S+T,+,X}" ... Summary: **Description** This makes `WidenIV::widenIVUse` (IndVarSimplify.cpp) fail to widen narrow IV uses in some cases. The latter affects IndVarSimplify which may not eliminate narrow IV's when there actually exists such a possibility, thereby producing ineffective code. When `WidenIV::widenIVUse` gets a NarrowUse such as `{(-2 + %inc.lcssa),+,1}<nsw><%for.body3>`, it first tries to get a wide recurrence for it via the `getWideRecurrence` call. `getWideRecurrence` returns recurrence like this: `{(sext i32 (-2 + %inc.lcssa) to i64),+,1}<nsw><%for.body3>`. Then a wide use operation is generated by `cloneIVUser`. The generated wide use is evaluated to `{(-2 + (sext i32 %inc.lcssa to i64))<nsw>,+,1}<nsw><%for.body3>`, which is different from the `getWideRecurrence` result. `cloneIVUser` sees the difference and returns nullptr. This patch also fixes the broken LLVM tests by adding missing <nsw> entries introduced by the correction. **Minimal reproducer:** ``` int foo(int a, int b, int c); int baz(); void bar() { int arr[20]; int i = 0; for (i = 0; i < 4; ++i) arr[i] = baz(); for (; i < 20; ++i) arr[i] = foo(arr[i - 4], arr[i - 3], arr[i - 2]); } ``` **Clang command line:** ``` clang++ -mllvm -debug -S -emit-llvm -O3 --target=aarch64-linux-elf test.cpp -o test.ir ``` **Expected result:** The ` -mllvm -debug` log shows that all the IV's for the second `for` loop have been eliminated. Reviewers: sanjoy Subscribers: atrick, asl, aemerson, mzolotukhin, llvm-commits Differential Revision: http://reviews.llvm.org/D20058 llvm-svn: 270695		2016-05-25 13:01:33 +00:00
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backward-dep-different-types.ll
forward-loop-carried.ll
forward-loop-independent.ll
independent-interleaved.ll	[LAA] Check independence of strided accesses before forward case	2016-05-19 15:37:19 +00:00
interleave-innermost.ll
memcheck-for-loop-invariant.ll
non-wrapping-pointer.ll
nullptr.ll
number-of-memchecks.ll	[SCEV] No-wrap flags are not propagated when folding "{S,+,X}+T ==> {S+T,+,X}"	2016-05-25 13:01:33 +00:00
pointer-with-unknown-bounds.ll
resort-to-memchecks-only.ll
reverse-memcheck-bounds.ll	[SCEV] No-wrap flags are not propagated when folding "{S,+,X}+T ==> {S+T,+,X}"	2016-05-25 13:01:33 +00:00
safe-no-checks.ll
safe-with-dep-distance.ll	[LAA] Include MaxSafeDepDistBytes in the analysis print-out	2016-05-13 22:49:13 +00:00
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