[PATCH] D89187: [AMDGPU] Minimize number of s_mov generated by copyPhysReg

[Carl Ritson via Phabricator via llvm-commits]

critson added a comment.

To motivate the peephole.
This pattern effects 2% of graphics shaders on GFX9, and nearly 7% on GFX10.
On average we save ~1.5 instructions per effected shader.
On some VulkanCTS tests the savings are much higher.
Given the relatively low gain, I assume it was not worth introducing a new peephole pass, and took this approach to address the duplicate s_mov instructions at the point of generation (when they cheapest to spot).


Repository:
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https://reviews.llvm.org/D89187