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72f01d1369
Summary:
Reduce the statefulness of the algorithm in two ways:
1. More clearly split generateWaitcntInstBefore into two phases: the
first one which determines the required wait, if any, without changing
the ScoreBrackets, and the second one which actually inserts the wait
and updates the brackets.
2. Communicate pre-existing s_waitcnt instructions using an argument to
generateWaitcntInstBefore instead of through the ScoreBrackets.
To simplify these changes, a Waitcnt structure is introduced which carries
the counts of an s_waitcnt instruction in decoded form.
There are some functional changes:
1. The FIXME for the VCCZ bug workaround was implemented: we only wait for
SMEM instructions as required instead of waiting on all counters.
2. We now properly track pre-existing waitcnt's in all cases, which leads
to less conservative waitcnts being emitted in some cases.
s_load_dword ...
s_waitcnt lgkmcnt(0) <-- pre-existing wait count
ds_read_b32 v0, ...
ds_read_b32 v1, ...
s_waitcnt lgkmcnt(0) <-- this is too conservative
use(v0)
more code
use(v1)
This increases code size a bit, but the reduced latency should still be a
win in basically all cases. The worst code size regressions in my shader-db
are:
WORST REGRESSIONS - Code Size
Before After Delta Percentage
1724 1736 12 0.70 % shaders/private/f1-2015/1334.shader_test [0]
2276 2284 8 0.35 % shaders/private/f1-2015/1306.shader_test [0]
4632 4640 8 0.17 % shaders/private/ue4_elemental/62.shader_test [0]
2376 2384 8 0.34 % shaders/private/f1-2015/1308.shader_test [0]
3284 3292 8 0.24 % shaders/private/talos_principle/1955.shader_test [0]
Reviewers: msearles, rampitec, scott.linder, kanarayan
Subscribers: arsenm, kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, t-tye, llvm-commits, hakzsam
Differential Revision: https://reviews.llvm.org/D54226
llvm-svn: 347848
38 lines
1.8 KiB
YAML
38 lines
1.8 KiB
YAML
# RUN: llc -march=amdgcn -verify-machineinstrs -run-pass si-insert-waitcnts -o - %s | FileCheck -check-prefixes=GCN %s
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# GCN-LABEL: name: test{{$}}
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# GCN: S_WAITCNT -16257
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# GGN: DS_READ2_B32
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# GGN: DS_READ2_B32
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# GCN: S_WAITCNT 383{{$}}
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# GCN-NEXT: $vgpr1 = V_ADD_U32_e32 1, killed $vgpr1, implicit $exec
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# GCN-NEXT: $vgpr1 = V_MAX_U32_e32 killed $vgpr0, killed $vgpr1, implicit $exec
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# GCN-NEXT: S_WAITCNT 127{{$}}
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# GCN-NEXT: $vgpr1 = V_MAX_U32_e32 killed $vgpr2, killed $vgpr1, implicit $exec
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--- |
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define amdgpu_cs void @test() {
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ret void
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}
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...
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---
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name: test
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body: |
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bb.0:
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liveins: $sgpr0, $sgpr1, $vgpr0
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renamable $sgpr0_sgpr1_sgpr2_sgpr3_sgpr4_sgpr5_sgpr6_sgpr7 = S_LOAD_DWORDX8_IMM renamable $sgpr0_sgpr1, 480, 0
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renamable $vgpr13 = V_LSHLREV_B32_e32 2, killed $vgpr0, implicit $exec
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S_WAITCNT -16257
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renamable $vgpr0_vgpr1 = DS_READ2_B32 renamable $vgpr13, 0, 1, 0, implicit $m0, implicit $exec
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renamable $vgpr2_vgpr3 = DS_READ2_B32 renamable $vgpr13, 2, 3, 0, implicit $m0, implicit $exec
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renamable $vgpr1 = V_ADD_U32_e32 1, killed $vgpr1, implicit $exec
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renamable $vgpr1 = V_MAX_U32_e32 killed $vgpr0, killed $vgpr1, implicit $exec
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renamable $vgpr1 = V_MAX_U32_e32 killed $vgpr2, killed $vgpr1, implicit $exec
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renamable $vgpr1 = V_MAX_U32_e32 killed $vgpr3, killed $vgpr1, implicit $exec
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$vgpr0 = V_MOV_B32_e32 $vgpr1, implicit $exec, implicit $exec
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$vgpr2 = V_MOV_B32_e32 $vgpr1, implicit $exec, implicit $exec
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$vgpr3 = V_MOV_B32_e32 $vgpr1, implicit $exec, implicit $exec
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IMAGE_STORE_V4_V2 killed renamable $vgpr0_vgpr1_vgpr2_vgpr3, killed renamable $vgpr0_vgpr1, killed renamable $sgpr0_sgpr1_sgpr2_sgpr3_sgpr4_sgpr5_sgpr6_sgpr7, 15, -1, 1, 0, 0, 0, 0, 0, 0, implicit $exec
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S_ENDPGM
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...
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