AMDGPU: Raise the priority of MAD24 in instruction selection.

Summary:
  We have seen performance regression when v_add3 is generated. The major reason is that the v_mad pattern
is broken when v_add3 is generated. We also see the register pressure increased. While we could not properly
estimate register pressure during instruction selection, we can give mad a higher priority.

In this work, we raise the priority for mad24 in selection and resolve the performance regression.

Reviewers:
  rampitec

Differential Revision:
  https://reviews.llvm.org/D56745

llvm-svn: 351273

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUInstructions.td b/llvm/lib/Target/AMDGPU/AMDGPUInstructions.td
index 282d1c11833..eb8f2002ff2 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUInstructions.td
+++ b/llvm/lib/Target/AMDGPU/AMDGPUInstructions.td
@@ -842,6 +842,7 @@ def cvt_flr_i32_f32 : PatFrag <
   [{ (void)N; return TM.Options.NoNaNsFPMath; }]
 >;
 
+let AddedComplexity = 2 in {
 class IMad24Pat<Instruction Inst, bit HasClamp = 0> : AMDGPUPat <
   (add (AMDGPUmul_i24 i32:$src0, i32:$src1), i32:$src2),
   !if(HasClamp, (Inst $src0, $src1, $src2, (i1 0)),
@@ -853,6 +854,7 @@ class UMad24Pat<Instruction Inst, bit HasClamp = 0> : AMDGPUPat <
   !if(HasClamp, (Inst $src0, $src1, $src2, (i1 0)),
                 (Inst $src0, $src1, $src2))
 >;
+} // AddedComplexity.
 
 class RcpPat<Instruction RcpInst, ValueType vt> : AMDGPUPat <
   (fdiv FP_ONE, vt:$src),