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d4bdf4737d
This patch is a generalization of the improvement introduced in rL296898. Previously, we were able to peel one iteration of a loop to get rid of a Phi that becomes an invariant on the 2nd iteration. In more general case, if a Phi becomes invariant after N iterations, we can peel N times and turn it into invariant. In order to do this, we for every Phi in loop's header we define the Invariant Depth value which is calculated as follows: Given %x = phi <Inputs from above the loop>, ..., [%y, %back.edge]. If %y is a loop invariant, then Depth(%x) = 1. If %y is a Phi from the loop header, Depth(%x) = Depth(%y) + 1. Otherwise, Depth(%x) is infinite. Notice that if we peel a loop, all Phis with Depth = 1 become invariants, and all other Phis with finite depth decrease the depth by 1. Thus, peeling N first iterations allows us to turn all Phis with Depth <= N into invariants. Reviewers: reames, apilipenko, mkuper, skatkov, anna, sanjoy Reviewed By: sanjoy Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D31613 llvm-svn: 300446 |
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| Analysis | ||
| AsmParser | ||
| Bitcode | ||
| CodeGen | ||
| DebugInfo | ||
| Demangle | ||
| ExecutionEngine | ||
| Fuzzer | ||
| IR | ||
| IRReader | ||
| LibDriver | ||
| LineEditor | ||
| Linker | ||
| LTO | ||
| MC | ||
| Object | ||
| ObjectYAML | ||
| Option | ||
| Passes | ||
| ProfileData | ||
| Support | ||
| TableGen | ||
| Target | ||
| Transforms | ||
| XRay | ||
| CMakeLists.txt | ||
| LLVMBuild.txt | ||