[PATCH] D148509: [BranchFolder] Skip redundant IMPLICIT_DEFs of subregs

[Jay Foad via Phabricator via llvm-commits]

foad created this revision.
foad added reviewers: AMDGPU, Pierre-vh, MatzeB, kparzysz.
Herald added subscribers: kosarev, StephenFan, kerbowa, hiraditya, jvesely.
Herald added a project: All.
foad requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D148509

Files:
  llvm/lib/CodeGen/BranchFolding.cpp
  llvm/test/CodeGen/AMDGPU/resource-usage-agpr-hi16.ll


Index: llvm/test/CodeGen/AMDGPU/resource-usage-agpr-hi16.ll
===================================================================
--- llvm/test/CodeGen/AMDGPU/resource-usage-agpr-hi16.ll
+++ llvm/test/CodeGen/AMDGPU/resource-usage-agpr-hi16.ll
@@ -37,20 +37,10 @@
   ; GFX90A-NEXT:   renamable $sgpr34_sgpr35 = S_MOV_B64 0
   ; GFX90A-NEXT:   renamable $vcc = S_AND_B64 $exec, renamable $sgpr30_sgpr31, implicit-def dead $scc
   ; GFX90A-NEXT:   $vgpr24 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $vgpr24_lo16 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $vgpr24_hi16 = IMPLICIT_DEF
   ; GFX90A-NEXT:   $agpr0 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $agpr0_lo16 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $agpr0_hi16 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $vgpr26_lo16 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $vgpr26_hi16 = IMPLICIT_DEF
   ; GFX90A-NEXT:   $vgpr26 = IMPLICIT_DEF
   ; GFX90A-NEXT:   $vgpr20 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $vgpr20_lo16 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $vgpr20_hi16 = IMPLICIT_DEF
   ; GFX90A-NEXT:   $vgpr22 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $vgpr22_lo16 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $vgpr22_hi16 = IMPLICIT_DEF
   ; GFX90A-NEXT:   S_CBRANCH_VCCNZ %bb.58, implicit $vcc
   ; GFX90A-NEXT: {{  $}}
   ; GFX90A-NEXT: bb.2:
@@ -583,11 +573,7 @@
   ; GFX90A-NEXT:   renamable $vgpr63, dead renamable $vcc = V_ADDC_U32_e64 0, $vgpr41, killed $vcc, 0, implicit $exec
   ; GFX90A-NEXT:   renamable $vcc = S_AND_B64 $exec, renamable $sgpr48_sgpr49, implicit-def dead $scc
   ; GFX90A-NEXT:   $agpr0 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $agpr0_lo16 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $agpr0_hi16 = IMPLICIT_DEF
   ; GFX90A-NEXT:   $vgpr14 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $vgpr14_lo16 = IMPLICIT_DEF
-  ; GFX90A-NEXT:   $vgpr14_hi16 = IMPLICIT_DEF
   ; GFX90A-NEXT:   S_CBRANCH_VCCNZ %bb.48, implicit $vcc
   ; GFX90A-NEXT: {{  $}}
   ; GFX90A-NEXT: bb.44:
Index: llvm/lib/CodeGen/BranchFolding.cpp
===================================================================
--- llvm/lib/CodeGen/BranchFolding.cpp
+++ llvm/lib/CodeGen/BranchFolding.cpp
@@ -860,6 +860,19 @@
       for (Register Reg : NewLiveIns) {
         if (!LiveRegs.available(*MRI, Reg))
           continue;
+
+        // Skip the register if we are about to add one of its super registers.
+        // TODO: Common this up with the same logic in addLineIns().
+        bool ContainsSuperReg = false;
+        for (MCSuperRegIterator SReg(Reg, TRI); SReg.isValid(); ++SReg) {
+          if (NewLiveIns.contains(*SReg) && !MRI->isReserved(*SReg)) {
+            ContainsSuperReg = true;
+            break;
+          }
+        }
+        if (ContainsSuperReg)
+          continue;
+
         DebugLoc DL;
         BuildMI(*Pred, InsertBefore, DL, TII->get(TargetOpcode::IMPLICIT_DEF),
                 Reg);


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