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34bf60ca68
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
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| .. | ||
| backward-dep-different-types.ll | ||
| forward-loop-carried.ll | ||
| forward-loop-independent.ll | ||
| independent-interleaved.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 | ||
| safe-with-dep-distance.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 | ||