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llvm-mirror/lib/Target/AMDGPU/AMDGPUCombine.td
Amara Emerson a7636dc8f8 [GlobalISel] Rewrite the elide-br-by-swapping-icmp-ops combine to do less.
This combine previously tried to take sequences like:
  %cond = G_ICMP pred, a, b
  G_BRCOND %cond, %truebb
  G_BR %falsebb
%truebb:
  ...
%falsebb:
  ...

and by inverting the compare predicate and swapping branch targets, delete the
G_BR and instead have a single conditional branch to the falsebb. Since in an
earlier patch we have a combine to fold not(icmp) into just an inverted icmp,
we don't need this combine to do as much. This patch instead generalizes the
combine by just looking for:
  G_BRCOND %cond, %truebb
  G_BR %falsebb
%truebb:
  ...
%falsebb:
  ...

and then inverting the condition using a not (xor). The xor can be folded away
in a separate combine. This change also lets us avoid some optimization code
in the IRTranslator.

I also think that deleting G_BRs in the combiner is unnecessary. That's
something that targets can decide to do at selection time and could simplify
generic code in future.

Differential Revision: https://reviews.llvm.org/D86664
2020-09-09 13:08:16 -07:00

60 lines
2.4 KiB
TableGen

//=- AMDGPUCombine.td - Define AMDGPU Combine Rules ----------*- tablegen -*-=//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
include "llvm/Target/GlobalISel/Combine.td"
// TODO: This really belongs after legalization after scalarization.
// TODO: GICombineRules should accept subtarget predicates
def fmin_fmax_legacy_matchdata : GIDefMatchData<"FMinFMaxLegacyInfo">;
def fcmp_select_to_fmin_fmax_legacy : GICombineRule<
(defs root:$select, fmin_fmax_legacy_matchdata:$matchinfo),
(match (wip_match_opcode G_SELECT):$select,
[{ return matchFMinFMaxLegacy(*${select}, MRI, *MF, ${matchinfo}); }]),
(apply [{ applySelectFCmpToFMinToFMaxLegacy(*${select}, ${matchinfo}); }])>;
def uchar_to_float : GICombineRule<
(defs root:$itofp),
(match (wip_match_opcode G_UITOFP, G_SITOFP):$itofp,
[{ return matchUCharToFloat(*${itofp}, MRI, *MF, Helper); }]),
(apply [{ applyUCharToFloat(*${itofp}); }])>;
def cvt_f32_ubyteN_matchdata : GIDefMatchData<"CvtF32UByteMatchInfo">;
def cvt_f32_ubyteN : GICombineRule<
(defs root:$cvt_f32_ubyteN, cvt_f32_ubyteN_matchdata:$matchinfo),
(match (wip_match_opcode G_AMDGPU_CVT_F32_UBYTE0,
G_AMDGPU_CVT_F32_UBYTE1,
G_AMDGPU_CVT_F32_UBYTE2,
G_AMDGPU_CVT_F32_UBYTE3):$cvt_f32_ubyteN,
[{ return matchCvtF32UByteN(*${cvt_f32_ubyteN}, MRI, *MF, ${matchinfo}); }]),
(apply [{ applyCvtF32UByteN(*${cvt_f32_ubyteN}, ${matchinfo}); }])>;
// Combines which should only apply on SI/VI
def gfx6gfx7_combines : GICombineGroup<[fcmp_select_to_fmin_fmax_legacy]>;
def AMDGPUPreLegalizerCombinerHelper: GICombinerHelper<
"AMDGPUGenPreLegalizerCombinerHelper", [all_combines]> {
let DisableRuleOption = "amdgpuprelegalizercombiner-disable-rule";
}
def AMDGPUPostLegalizerCombinerHelper: GICombinerHelper<
"AMDGPUGenPostLegalizerCombinerHelper",
[all_combines, gfx6gfx7_combines,
uchar_to_float, cvt_f32_ubyteN]> {
let DisableRuleOption = "amdgpupostlegalizercombiner-disable-rule";
}
def AMDGPURegBankCombinerHelper : GICombinerHelper<
"AMDGPUGenRegBankCombinerHelper", []> {
let DisableRuleOption = "amdgpuregbankcombiner-disable-rule";
}