[PATCH] D127768: AMDGPU: Clear kill flags when optimizing vcmp save exec sequence

[Konstantin Zhuravlyov via Phabricator via llvm-commits]

kzhuravl created this revision.
kzhuravl added reviewers: arsenm, rampitec, tsymalla.
Herald added subscribers: kosarev, jsilvanus, hsmhsm, foad, kerbowa, hiraditya, t-tye, tpr, dstuttard, yaxunl, nhaehnle, jvesely.
Herald added a project: All.
kzhuravl requested review of this revision.
Herald added a subscriber: wdng.
Herald added a project: LLVM.

It was causing bad machine code for several blender scenes:

  - Bad machine code: Using an undefined physical register ***
- function:    kernel_holdout_emission_blurring_pathtermination_ao
- basic block: %bb.28 if.end40.i (0x7f84861a2320)
- instruction: V_CMPX_EQ_U32_nosdst_e64 0, $vgpr3, implicit-def $exec, implicit $exec
- operand 1:   $vgpr3


https://reviews.llvm.org/D127768

Files:
  llvm/lib/Target/AMDGPU/SIOptimizeExecMasking.cpp
  llvm/test/CodeGen/AMDGPU/vcmp-saveexec-to-vcmpx-wrong-kill-flags.mir


Index: llvm/test/CodeGen/AMDGPU/vcmp-saveexec-to-vcmpx-wrong-kill-flags.mir
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AMDGPU/vcmp-saveexec-to-vcmpx-wrong-kill-flags.mir
@@ -0,0 +1,21 @@
+# RUN: llc -march=amdgcn -mcpu=gfx1030 -run-pass=si-optimize-exec-masking -verify-machineinstrs %s -o - | FileCheck -check-prefix=GFX1030 %s
+
+---
+
+# GFX1030-LABEL: name: vcmp_saveexec_to_vcmpx_wrong_kill_flags
+# GFX1030: V_CMP_NE_U32_e64 0, $vgpr0, implicit $exec
+# GFX1030: V_CMPX_EQ_U32_nosdst_e64 0, $vgpr0, implicit-def $exec, implicit $exec
+name: vcmp_saveexec_to_vcmpx_wrong_kill_flags
+tracksRegLiveness: true
+body: |
+  bb.0:
+    liveins: $sgpr43, $sgpr44, $sgpr45, $sgpr55, $sgpr62, $sgpr63, $sgpr64, $sgpr65, $sgpr66, $sgpr67, $vgpr40, $vgpr41, $vgpr76, $vgpr77, $vgpr78, $vgpr95, $vgpr109, $vgpr110, $vgpr111, $sgpr48_sgpr49_sgpr50_sgpr51:0x000000000000000C, $sgpr52_sgpr53_sgpr54_sgpr55:0x0000000000000003, $sgpr34_sgpr35, $sgpr36_sgpr37, $sgpr38_sgpr39, $sgpr40_sgpr41, $sgpr56_sgpr57, $sgpr58_sgpr59, $sgpr60_sgpr61, $vgpr92_vgpr93_vgpr94_vgpr95:0x000000000000003F, $vgpr104_vgpr105_vgpr106_vgpr107:0x000000000000003F, $vgpr46_vgpr47:0x000000000000000F, $vgpr60_vgpr61:0x000000000000000F, $vgpr62_vgpr63:0x000000000000000C, $vgpr72_vgpr73:0x000000000000000F, $vgpr74_vgpr75:0x000000000000000F, $vgpr88_vgpr89:0x000000000000000C, $vgpr90_vgpr91:0x0000000000000003, $vgpr124_vgpr125:0x000000000000000F, $vgpr126_vgpr127:0x000000000000000F
+  
+    renamable $vgpr0 = V_AND_B32_e32 128, $vgpr90, implicit $exec
+    renamable $vcc_lo = V_CMP_EQ_U32_e64 0, $vgpr0, implicit $exec
+    renamable $sgpr4 = V_CMP_NE_U32_e64 0, killed $vgpr0, implicit $exec
+    renamable $sgpr48 = S_MOV_B32 0
+    renamable $sgpr68 = COPY renamable $sgpr66
+    renamable $sgpr5 = COPY $exec_lo, implicit-def $exec_lo
+    renamable $sgpr6 = S_AND_B32 renamable $sgpr5, killed renamable $vcc_lo, implicit-def dead $scc
+    $exec_lo = S_MOV_B32_term killed renamable $sgpr6
Index: llvm/lib/Target/AMDGPU/SIOptimizeExecMasking.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/SIOptimizeExecMasking.cpp
+++ llvm/lib/Target/AMDGPU/SIOptimizeExecMasking.cpp
@@ -488,6 +488,9 @@
 
   TryAddImmediateValueFromNamedOperand(AMDGPU::OpName::clamp);
 
+  // The kill flags on Src1 may no longer be correct.
+  MRI.clearKillFlags(Src1->getReg());
+
   return true;
 }
 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D127768.436849.patch
Type: text/x-patch
Size: 2480 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20220614/97567161/attachment.bin>