[PATCH] D47805: [AMDGPU] Improve reciprocal handling
Stanislav Mekhanoshin via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Jun 5 17:25:23 PDT 2018
rampitec created this revision.
rampitec added reviewers: b-sumner, arsenm.
Herald added subscribers: t-tye, Anastasia, tpr, dstuttard, yaxunl, nhaehnle, wdng, kzhuravl.
When denormals are supported we are producing a full division for
1.0f / x. That still can be replaced by the faster version:
bool c = fabs(x) > 0x1.0p+96f;
float s = c ? 0x1.0p-32f : 1.0f;
x *= s;
return s * v_rcp_f32(x)
in case if requested accuracy is 2.5ulp or less. The same version
is used if denormals are not supported for non 1.0 numerators, where
just v_rcp_f32 is then used for 1.0 numerator.
The optimization of 1/x is extended to the case -1/x, which is the
same except for the resulting sign bit.
OpenCL conformance passed with both enabled and disabled denorms.
https://reviews.llvm.org/D47805
Files:
lib/Target/AMDGPU/AMDGPUCodeGenPrepare.cpp
test/CodeGen/AMDGPU/fdiv32-to-rcp-folding.ll
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