[all-commits] [llvm/llvm-project] 9801e5: [AMDGPU] Disable nested endcf collapse

[Stanislav Mekhanoshin via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 9801e5469b4e4cbf93b80eb57f8dfeabf65f6714
      https://github.com/llvm/llvm-project/commit/9801e5469b4e4cbf93b80eb57f8dfeabf65f6714
  Author: Stanislav Mekhanoshin <Stanislav.Mekhanoshin at amd.com>
  Date:   2020-03-11 (Wed, 11 Mar 2020)

  Changed paths:
    M llvm/lib/Target/AMDGPU/SIOptimizeExecMaskingPreRA.cpp
    M llvm/test/CodeGen/AMDGPU/collapse-endcf.ll
    M llvm/test/CodeGen/AMDGPU/collapse-endcf.mir

  Log Message:
  -----------
  [AMDGPU] Disable nested endcf collapse

The assumption is that conditional regions are perfectly nested
and a mask restored at the exit from the inner block will be
completely covered by a mask restored in the outer.

It turns out with our current structurizer this is not always
the case.

Disable the optimization for now, but I want to keep it around
for a while to either try after further structurizer changes or
to move it into control flow lowering where we have more info
and reuse the test.

Differential Revision: https://reviews.llvm.org/D75958