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llvm-project/llvm/test/CodeGen/AMDGPU/wqm.mir

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[AMDGPU] Add support for Whole Wavefront Mode Summary: Whole Wavefront Wode (WWM) is similar to WQM, except that all of the lanes are always enabled, regardless of control flow. This is required for implementing wavefront reductions in non-uniform control flow, where we need to use the inactive lanes to propagate intermediate results, so they need to be enabled. We need to propagate WWM to uses (unless they're explicitly marked as exact) so that they also propagate intermediate results correctly. We do the analysis and exec mask munging during the WQM pass, since there are interactions with WQM for things that require both WQM and WWM. For simplicity, WWM is entirely block-local -- blocks are never WWM on entry or exit of a block, and WWM is not propagated to the block level. This means that computations involving WWM cannot involve control flow, but we only ever plan to use WWM for a few limited purposes (none of which involve control flow) anyways. Shaders can ask for WWM using the @llvm.amdgcn.wwm intrinsic. There isn't yet a way to turn WWM off -- that will be added in a future change. Finally, it turns out that turning on inactive lanes causes a number of problems with register allocation. While the best long-term solution seems like teaching LLVM's register allocator about predication, for now we need to add some hacks to prevent ourselves from getting into trouble due to constraints that aren't currently expressed in LLVM. For the gory details, see the comments at the top of SIFixWWMLiveness.cpp. Reviewers: arsenm, nhaehnle, tpr Subscribers: kzhuravl, wdng, mgorny, yaxunl, dstuttard, t-tye, llvm-commits Differential Revision: https://reviews.llvm.org/D35524 llvm-svn: 310087
2017-08-05 02:36:52 +08:00
# RUN: llc -march=amdgcn -verify-machineinstrs -run-pass si-wqm -o - %s | FileCheck %s
---
# Check for awareness that s_or_saveexec_b64 clobbers SCC
#
#CHECK: S_OR_SAVEEXEC_B64
#CHECK: S_CMP_LT_I32
#CHECK: S_CSELECT_B32
name: test_wwm_scc
alignment: 0
exposesReturnsTwice: false
legalized: false
regBankSelected: false
selected: false
tracksRegLiveness: true
registers:
- { id: 0, class: sgpr_32, preferred-register: '' }
- { id: 1, class: sgpr_32, preferred-register: '' }
- { id: 2, class: sgpr_32, preferred-register: '' }
- { id: 3, class: vgpr_32, preferred-register: '' }
- { id: 4, class: vgpr_32, preferred-register: '' }
- { id: 5, class: sgpr_32, preferred-register: '' }
- { id: 6, class: vgpr_32, preferred-register: '' }
- { id: 7, class: vgpr_32, preferred-register: '' }
- { id: 8, class: sreg_32_xm0, preferred-register: '' }
- { id: 9, class: sreg_32, preferred-register: '' }
- { id: 10, class: sreg_32, preferred-register: '' }
- { id: 11, class: vgpr_32, preferred-register: '' }
- { id: 12, class: vgpr_32, preferred-register: '' }
liveins:
Followup on Proposal to move MIR physical register namespace to '$' sigil. Discussed here: http://lists.llvm.org/pipermail/llvm-dev/2018-January/120320.html In preparation for adding support for named vregs we are changing the sigil for physical registers in MIR to '$' from '%'. This will prevent name clashes of named physical register with named vregs. llvm-svn: 323922
2018-02-01 06:04:26 +08:00
- { reg: '$sgpr0', virtual-reg: '%0' }
- { reg: '$sgpr1', virtual-reg: '%1' }
- { reg: '$sgpr2', virtual-reg: '%2' }
- { reg: '$vgpr0', virtual-reg: '%3' }
[AMDGPU] Add support for Whole Wavefront Mode Summary: Whole Wavefront Wode (WWM) is similar to WQM, except that all of the lanes are always enabled, regardless of control flow. This is required for implementing wavefront reductions in non-uniform control flow, where we need to use the inactive lanes to propagate intermediate results, so they need to be enabled. We need to propagate WWM to uses (unless they're explicitly marked as exact) so that they also propagate intermediate results correctly. We do the analysis and exec mask munging during the WQM pass, since there are interactions with WQM for things that require both WQM and WWM. For simplicity, WWM is entirely block-local -- blocks are never WWM on entry or exit of a block, and WWM is not propagated to the block level. This means that computations involving WWM cannot involve control flow, but we only ever plan to use WWM for a few limited purposes (none of which involve control flow) anyways. Shaders can ask for WWM using the @llvm.amdgcn.wwm intrinsic. There isn't yet a way to turn WWM off -- that will be added in a future change. Finally, it turns out that turning on inactive lanes causes a number of problems with register allocation. While the best long-term solution seems like teaching LLVM's register allocator about predication, for now we need to add some hacks to prevent ourselves from getting into trouble due to constraints that aren't currently expressed in LLVM. For the gory details, see the comments at the top of SIFixWWMLiveness.cpp. Reviewers: arsenm, nhaehnle, tpr Subscribers: kzhuravl, wdng, mgorny, yaxunl, dstuttard, t-tye, llvm-commits Differential Revision: https://reviews.llvm.org/D35524 llvm-svn: 310087
2017-08-05 02:36:52 +08:00
body: |
bb.0:
Followup on Proposal to move MIR physical register namespace to '$' sigil. Discussed here: http://lists.llvm.org/pipermail/llvm-dev/2018-January/120320.html In preparation for adding support for named vregs we are changing the sigil for physical registers in MIR to '$' from '%'. This will prevent name clashes of named physical register with named vregs. llvm-svn: 323922
2018-02-01 06:04:26 +08:00
liveins: $sgpr0, $sgpr1, $sgpr2, $vgpr0
[AMDGPU] Add support for Whole Wavefront Mode Summary: Whole Wavefront Wode (WWM) is similar to WQM, except that all of the lanes are always enabled, regardless of control flow. This is required for implementing wavefront reductions in non-uniform control flow, where we need to use the inactive lanes to propagate intermediate results, so they need to be enabled. We need to propagate WWM to uses (unless they're explicitly marked as exact) so that they also propagate intermediate results correctly. We do the analysis and exec mask munging during the WQM pass, since there are interactions with WQM for things that require both WQM and WWM. For simplicity, WWM is entirely block-local -- blocks are never WWM on entry or exit of a block, and WWM is not propagated to the block level. This means that computations involving WWM cannot involve control flow, but we only ever plan to use WWM for a few limited purposes (none of which involve control flow) anyways. Shaders can ask for WWM using the @llvm.amdgcn.wwm intrinsic. There isn't yet a way to turn WWM off -- that will be added in a future change. Finally, it turns out that turning on inactive lanes causes a number of problems with register allocation. While the best long-term solution seems like teaching LLVM's register allocator about predication, for now we need to add some hacks to prevent ourselves from getting into trouble due to constraints that aren't currently expressed in LLVM. For the gory details, see the comments at the top of SIFixWWMLiveness.cpp. Reviewers: arsenm, nhaehnle, tpr Subscribers: kzhuravl, wdng, mgorny, yaxunl, dstuttard, t-tye, llvm-commits Differential Revision: https://reviews.llvm.org/D35524 llvm-svn: 310087
2017-08-05 02:36:52 +08:00
Followup on Proposal to move MIR physical register namespace to '$' sigil. Discussed here: http://lists.llvm.org/pipermail/llvm-dev/2018-January/120320.html In preparation for adding support for named vregs we are changing the sigil for physical registers in MIR to '$' from '%'. This will prevent name clashes of named physical register with named vregs. llvm-svn: 323922
2018-02-01 06:04:26 +08:00
%3 = COPY $vgpr0
%2 = COPY $sgpr2
%1 = COPY $sgpr1
%0 = COPY $sgpr0
S_CMP_LT_I32 0, %0, implicit-def $scc
%12 = V_ADD_I32_e32 %3, %3, implicit-def $vcc, implicit $exec
%5 = S_CSELECT_B32 %2, %1, implicit $scc
%11 = V_ADD_I32_e32 %5, %12, implicit-def $vcc, implicit $exec
$vgpr0 = WWM %11, implicit $exec
SI_RETURN_TO_EPILOG $vgpr0
[AMDGPU] Add support for Whole Wavefront Mode Summary: Whole Wavefront Wode (WWM) is similar to WQM, except that all of the lanes are always enabled, regardless of control flow. This is required for implementing wavefront reductions in non-uniform control flow, where we need to use the inactive lanes to propagate intermediate results, so they need to be enabled. We need to propagate WWM to uses (unless they're explicitly marked as exact) so that they also propagate intermediate results correctly. We do the analysis and exec mask munging during the WQM pass, since there are interactions with WQM for things that require both WQM and WWM. For simplicity, WWM is entirely block-local -- blocks are never WWM on entry or exit of a block, and WWM is not propagated to the block level. This means that computations involving WWM cannot involve control flow, but we only ever plan to use WWM for a few limited purposes (none of which involve control flow) anyways. Shaders can ask for WWM using the @llvm.amdgcn.wwm intrinsic. There isn't yet a way to turn WWM off -- that will be added in a future change. Finally, it turns out that turning on inactive lanes causes a number of problems with register allocation. While the best long-term solution seems like teaching LLVM's register allocator about predication, for now we need to add some hacks to prevent ourselves from getting into trouble due to constraints that aren't currently expressed in LLVM. For the gory details, see the comments at the top of SIFixWWMLiveness.cpp. Reviewers: arsenm, nhaehnle, tpr Subscribers: kzhuravl, wdng, mgorny, yaxunl, dstuttard, t-tye, llvm-commits Differential Revision: https://reviews.llvm.org/D35524 llvm-svn: 310087
2017-08-05 02:36:52 +08:00
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