[PATCH] D18162: AMDGPU: Add SIWholeQuadMode pass

Matt Arsenault via llvm-commits llvm-commits at lists.llvm.org
Mon Mar 21 10:56:57 PDT 2016

arsenm added a comment.

In http://reviews.llvm.org/D18162#378752, @nhaehnle wrote:


> The derivative taken by the llvm.SI.image.sample is undefined in GLSL if the control-flow is dynamically non-uniform, so it is perfectly legal to sink the llvm.amdgcn.image.load into the IF block (and the same applies to any other computation that leads to a derivative).

This is the same situation as barriers, so I think this should still be convergent. The problem it is solving is if LLVM introduces uses that do not hit uniform control flow, like introducing a call in either side of an if/then block


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