5a5d0fb1e4
For a loop like this
```
for (int j = 0; j < M; j++) {
if (N <= 0) continue; // invariant guard branches to latch
for (int i = 0; i < N; i++)
A[i] = B[i] + 1;
}
```
Since none of the successors of the guard branch of the inner loop are
outside the loop `j`, unswitching treats this as a non-trivial branch.
In reality, this is a perfect loop nest. If the condition of the guard
of `i` loop is false, there is nothing to do and so if we unswitch this
branch, the loop does not need to be versioned. This matches the
requirements of a trivial unswitch. This patch extends trivial loop
unswitching to catch cases like this.
The patch changes the loop guard so that instead of branching to the
latch of the outer loop, it exits the loop. This allows the existing code
for trivial unswitching to perform the transformation. The change in the
loop guard will happen only if all conditions for unswitching are met.
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| ci | ||
| cmake | ||
| docs | ||
| include/polly | ||
| lib | ||
| test | ||
| unittests | ||
| utils | ||
| www | ||
| .arclint | ||
| .gitattributes | ||
| .gitignore | ||
| CMakeLists.txt | ||
| CREDITS.txt | ||
| LICENSE.TXT | ||
| Maintainers.md | ||
| README | ||
Polly - Polyhedral optimizations for LLVM ----------------------------------------- http://polly.llvm.org/ Polly uses a mathematical representation, the polyhedral model, to represent and transform loops and other control flow structures. Using an abstract representation it is possible to reason about transformations in a more general way and to use highly optimized linear programming libraries to figure out the optimal loop structure. These transformations can be used to do constant propagation through arrays, remove dead loop iterations, optimize loops for cache locality, optimize arrays, apply advanced automatic parallelization, drive vectorization, or they can be used to do software pipelining.