[PATCH] D29620: [JumpThreading] Thread through guards

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev created this revision.

This patch allows JumpThreading also thread through guards.
Virtually, guard(cond) is equivalent to the following construction:

  if (cond) { do something } else {deoptimize}

Yet it is not explicitly converted into IFs before lowering.
This patch enables early threading through guards in simple cases.
Currently it covers the following situation:

if (cond1) {

  // code A

} else {

  // code B

}
// code C
guard(cond2)
// code D

If there is implication between cond1 and cond2, we can transform
this construction into the following:

if (cond1) {

  // code A
  // code C

} else {

  // code B
  // code C
  guard(cond2)

}
// code D

Thus, removing the guard from one of execution branches.


https://reviews.llvm.org/D29620

Files:
  include/llvm/Transforms/Scalar/JumpThreading.h
  lib/Transforms/Scalar/JumpThreading.cpp
  test/Transforms/JumpThreading/guards.ll

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