Commit Graph

6 Commits

Author SHA1 Message Date
Changpeng Fang 2531535984 AMDGPU: Implement FDIV optimizations in AMDGPUCodeGenPrepare
Summary:
      RCP has the accuracy limit. If FDIV fpmath require high accuracy rcp may not
    meet the requirement. However, in DAG lowering, fpmath information gets lost,
    and thus we may generate either inaccurate rcp related computation or slow code
    for fdiv.

    In patch implements fdiv optimizations in the AMDGPUCodeGenPrepare, which could
    exactly know !fpmath.

     FastUnsafeRcpLegal: We determine whether it is legal to use rcp based on
                         unsafe-fp-math, fast math flags, denormals and fpmath
                         accuracy request.

     RCP Optimizations:
       1/x -> rcp(x) when fast unsafe rcp is legal or fpmath >= 2.5ULP with
                                                      denormals flushed.
       a/b -> a*rcp(b) when fast unsafe rcp is legal.

     Use fdiv.fast:
       a/b -> fdiv.fast(a, b) when RCP optimization is not performed and
                              fpmath >= 2.5ULP with denormals flushed.

       1/x -> fdiv.fast(1,x)  when RCP optimization is not performed and
                              fpmath >= 2.5ULP with denormals.

    Reviewers:
      arsenm

    Differential Revision:
      https://reviews.llvm.org/D71293
2020-01-23 16:57:43 -08:00
Matt Arsenault 3dbeefa978 AMDGPU: Mark all unspecified CC functions in tests as amdgpu_kernel
Currently the default C calling convention functions are treated
the same as compute kernels. Make this explicit so the default
calling convention can be changed to a non-kernel.

Converted with perl -pi -e 's/define void/define amdgpu_kernel void/'
on the relevant test directories (and undoing in one place that actually
wanted a non-kernel).

llvm-svn: 298444
2017-03-21 21:39:51 +00:00
Matt Arsenault d8ed207a20 AMDGPU: Constant fold rcp node
When doing arcp optimization with a constant denominator,
this was leaving behind rcps with constant inputs.

llvm-svn: 297248
2017-03-08 00:48:46 +00:00
Matt Arsenault b2cb5f8105 AMDGPU: Simplify tests with per function subtargets
llvm-svn: 274971
2016-07-09 07:55:03 +00:00
Matt Arsenault b6d8c37e1a AMDGPU: Fold more custom nodes to undef
This will help sneak undefs past GVN into the DAG for
some tests.

Also add missing intrinsic for rsq_legacy, even though the node
was already selected to the instruction. Also start passing
the debug location to intrinsic errors.

llvm-svn: 273181
2016-06-20 18:33:56 +00:00
Matt Arsenault bef34e21c7 AMDGPU: Rename intrinsics to use amdgcn prefix
The intrinsic target prefix should match the target name
as it appears in the triple.

This is not yet complete, but gets most of the important ones.
llvm.AMDGPU.* intrinsics used by mesa and libclc are still handled
for compatability for now.

llvm-svn: 258557
2016-01-22 21:30:34 +00:00