AMDGPU: Don't delete cndmask with multiple uses in exec mask fold

[arsenm]

Summary

This was checking if this instruction killed it, but other uses
could appear before the kill.

[arsenm]

Correct version of patch

[arsenm]

Obsoleted by D128882

llvm/lib/Target/AMDGPU/SIOptimizeExecMaskingPreRA.cpp

bool SIOptimizeExecMaskingPreRA::optimizeVcndVcmpPair(MachineBasicBlock &MBB) {
   MachineOperand *Op1 = TII->getNamedOperand(*Cmp, AMDGPU::OpName::src0);
   MachineOperand *Op2 = TII->getNamedOperand(*Cmp, AMDGPU::OpName::src1);
   if (Op1->isImm() && Op2->isReg())
     std::swap(Op1, Op2);
   if (!Op1->isReg() || !Op2->isImm() || Op2->getImm() != 1)
     return false;
 
   Register SelReg = Op1->getReg();
+  if (SelReg.isPhysical())
+    return false;
+
   auto *Sel = TRI->findReachingDef(SelReg, Op1->getSubReg(), *Cmp, *MRI, LIS);
   if (!Sel || Sel->getOpcode() != AMDGPU::V_CNDMASK_B32_e64)
     return false;
 
   if (TII->hasModifiersSet(*Sel, AMDGPU::OpName::src0_modifiers) ||
       TII->hasModifiersSet(*Sel, AMDGPU::OpName::src1_modifiers))
     return false;
 
if ((CmpReg.isVirtual() && CmpLI->Query(AndIdx.getRegSlot()).isKill()) ||
                       return MI.readsRegister(CondReg, TRI);
                     }))) {
     LLVM_DEBUG(dbgs() << "Erasing: " << *Cmp << '\n');
     if (CmpLI)
       LIS->removeVRegDefAt(*CmpLI, CmpIdx.getRegSlot());
     LIS->RemoveMachineInstrFromMaps(*Cmp);
     Cmp->eraseFromParent();
 
-    LiveInterval *SelLI =
-        SelReg.isVirtual() ? &LIS->getInterval(SelReg) : nullptr;
-    // Try to remove v_cndmask_b32.
-    if (SelLI && SelLI->Query(CmpIdx.getRegSlot()).isKill()) {
-      LLVM_DEBUG(dbgs() << "Erasing: " << *Sel << '\n');
+    LiveInterval &SelLI = LIS->getInterval(SelReg);
 
-      if (SelLI)
-        LIS->removeVRegDefAt(*SelLI, SelIdx.getRegSlot());
+    // Try to remove v_cndmask_b32.
+    if (MRI->use_nodbg_empty(SelReg)) {
+      LLVM_DEBUG(dbgs() << "Erasing: " << *Sel);
+      LIS->removeVRegDefAt(SelLI, SelIdx.getRegSlot());
       LIS->RemoveMachineInstrFromMaps(*Sel);
       Sel->eraseFromParent();
-    }
+    } else
+      LIS->shrinkToUses(&SelLI);
   }
 
   if (CCReg.isVirtual()) {
     LiveInterval &CCLI = LIS->getInterval(CCReg);
     auto CCQ = CCLI.Query(SelIdx.getRegSlot());
     if (CCQ.valueIn()) {
       CCLI.addSegment(LiveRange::Segment(SelIdx.getRegSlot(),
                                          AndIdx.getRegSlot(), CCQ.valueIn()));

llvm/test/CodeGen/AMDGPU/opt-exec-masking-pre-ra-update-liveness.mir

body:             |
   ; CHECK-NEXT:   successors: %bb.4(0x80000000)
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT:   S_CBRANCH_VCCNZ %bb.4, implicit undef $vcc
   ; CHECK-NEXT:   S_BRANCH %bb.4
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT: bb.2:
   ; CHECK-NEXT:   successors: %bb.4(0x40000000), %bb.3(0x40000000)
   ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   dead %1:vgpr_32 = V_CNDMASK_B32_e64 0, 0, 0, 1, [[DEF]], implicit $exec
   ; CHECK-NEXT:   $vcc = S_ANDN2_B64 $exec, [[DEF]], implicit-def $scc
   ; CHECK-NEXT:   S_CBRANCH_VCCNZ %bb.4, implicit $vcc
   ; CHECK-NEXT:   S_BRANCH %bb.3
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT: bb.3:
   ; CHECK-NEXT:   successors: %bb.4(0x80000000)
   ; CHECK-NEXT: {{  $}}
-  ; CHECK-NEXT:   S_NOP 0, implicit undef %1:vgpr_32
+  ; CHECK-NEXT:   S_NOP 0, implicit undef %1
   ; CHECK-NEXT:   S_BRANCH %bb.4
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT: bb.4:
   bb.0:
     %0:sreg_64_xexec = IMPLICIT_DEF
     S_CBRANCH_VCCNZ %bb.2, implicit undef $vcc
 
   bb.1:
bb.2:
     S_CBRANCH_VCCNZ %bb.4, implicit $vcc
     S_BRANCH %bb.3
 
   bb.3:
     S_BRANCH %bb.4
 
   bb.4:
 ...
+
+# Can't delete V_CNDMASK_B32 when folding into the use in %bb.3 since
+# it's also used in %bb.0
+---
+name:            cndmask_multiple_uses
+tracksRegLiveness: true
+body:             |
+  ; CHECK-LABEL: name: cndmask_multiple_uses
+  ; CHECK: bb.0:
+  ; CHECK-NEXT:   successors: %bb.1(0x80000000)
+  ; CHECK-NEXT:   liveins: $vgpr0, $sgpr4_sgpr5, $sgpr6_sgpr7, $sgpr8_sgpr9, $sgpr10_sgpr11, $sgpr14, $sgpr15, $sgpr16
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[V_CNDMASK_B32_e64_:%[0-9]+]]:vgpr_32 = V_CNDMASK_B32_e64 0, 0, 0, 1, undef %1:sreg_64_xexec, implicit $exec
+  ; CHECK-NEXT:   [[V_CMP_NE_U32_e64_:%[0-9]+]]:sreg_64_xexec = V_CMP_NE_U32_e64 1, [[V_CNDMASK_B32_e64_]], implicit $exec
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.1:
+  ; CHECK-NEXT:   successors: %bb.3(0x40000000), %bb.2(0x40000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   S_CBRANCH_VCCNZ %bb.3, implicit undef $vcc
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.2:
+  ; CHECK-NEXT:   successors: %bb.5(0x40000000), %bb.3(0x40000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   $vcc = S_AND_B64 $exec, [[V_CMP_NE_U32_e64_]], implicit-def dead $scc
+  ; CHECK-NEXT:   S_CBRANCH_VCCNZ %bb.5, implicit $vcc
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.3:
+  ; CHECK-NEXT:   successors: %bb.5(0x40000000), %bb.4(0x40000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   $vcc = S_ANDN2_B64 $exec, undef %1:sreg_64_xexec, implicit-def dead $scc
+  ; CHECK-NEXT:   S_CBRANCH_VCCNZ %bb.5, implicit $vcc
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.4:
+  ; CHECK-NEXT:   successors: %bb.5(0x80000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.5:
+  bb.0:
+    liveins: $vgpr0, $sgpr4_sgpr5, $sgpr6_sgpr7, $sgpr8_sgpr9, $sgpr10_sgpr11, $sgpr14, $sgpr15, $sgpr16
+
+    %0:vgpr_32 = V_CNDMASK_B32_e64 0, 0, 0, 1, undef %1:sreg_64_xexec, implicit $exec
+    %2:sreg_64_xexec = V_CMP_NE_U32_e64 1, %0, implicit $exec
+
+  bb.1:
+    S_CBRANCH_VCCNZ %bb.3, implicit undef $vcc
+
+  bb.2:
+    $vcc = S_AND_B64 $exec, %2, implicit-def dead $scc
+    S_CBRANCH_VCCNZ %bb.6, implicit killed $vcc
+
+  bb.3:
+    %3:sreg_64_xexec = V_CMP_NE_U32_e64 1, %0, implicit $exec
+    $vcc = S_AND_B64 $exec, %3, implicit-def dead $scc
+    S_CBRANCH_VCCNZ %bb.6, implicit killed $vcc
+
+  bb.5:
+
+  bb.6:
+
+...
+
+# The live segment of %1 from V_CMP_GT_I32 needs to be shrunk after the use in %bb.1 is deleted
+---
+name:            leftover_use_of_selreg_extends_liverange
+tracksRegLiveness: true
+body:             |
+  ; CHECK-LABEL: name: leftover_use_of_selreg_extends_liverange
+  ; CHECK: bb.0:
+  ; CHECK-NEXT:   successors: %bb.2(0x40000000), %bb.1(0x40000000)
+  ; CHECK-NEXT:   liveins: $vgpr0, $sgpr4_sgpr5, $sgpr6_sgpr7, $sgpr8_sgpr9, $sgpr10_sgpr11, $sgpr14, $sgpr15, $sgpr16
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[DEF:%[0-9]+]]:sreg_64_xexec = IMPLICIT_DEF
+  ; CHECK-NEXT:   [[V_CNDMASK_B32_e64_:%[0-9]+]]:vgpr_32 = V_CNDMASK_B32_e64 0, 0, 0, 1, [[DEF]], implicit $exec
+  ; CHECK-NEXT:   [[V_CMP_GT_I32_e64_:%[0-9]+]]:sreg_64 = V_CMP_GT_I32_e64 0, [[V_CNDMASK_B32_e64_]], implicit $exec
+  ; CHECK-NEXT:   $exec = S_MOV_B64_term [[V_CMP_GT_I32_e64_]]
+  ; CHECK-NEXT:   S_CBRANCH_EXECZ %bb.2, implicit $exec
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.1:
+  ; CHECK-NEXT:   successors: %bb.3(0x40000000), %bb.2(0x40000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   $vcc = S_ANDN2_B64 $exec, [[DEF]], implicit-def dead $scc
+  ; CHECK-NEXT:   S_CBRANCH_VCCNZ %bb.3, implicit $vcc
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.2:
+  ; CHECK-NEXT:   successors: %bb.3(0x80000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.3:
+  bb.0:
+    liveins: $vgpr0, $sgpr4_sgpr5, $sgpr6_sgpr7, $sgpr8_sgpr9, $sgpr10_sgpr11, $sgpr14, $sgpr15, $sgpr16
+
+    %0:sreg_64_xexec = IMPLICIT_DEF
+    %1:vgpr_32 = V_CNDMASK_B32_e64 0, 0, 0, 1, %0, implicit $exec
+    %2:sreg_64 = V_CMP_GT_I32_e64 0, %1, implicit $exec
+    $exec = S_MOV_B64_term %2
+    S_CBRANCH_EXECZ %bb.2, implicit $exec
+
+  bb.1:
+    %3:sreg_64_xexec = V_CMP_NE_U32_e64 1, %1, implicit $exec
+    $vcc = S_AND_B64 $exec, %3, implicit-def dead $scc
+    S_CBRANCH_VCCNZ %bb.3, implicit killed $vcc
+
+  bb.2:
+
+  bb.3:
+
+...
+
+---
+name:            leftover_use_of_selreg_extends_liverange_subrange
+tracksRegLiveness: true
+body:             |
+  ; CHECK-LABEL: name: leftover_use_of_selreg_extends_liverange_subrange
+  ; CHECK: bb.0:
+  ; CHECK-NEXT:   successors: %bb.2(0x40000000), %bb.1(0x40000000)
+  ; CHECK-NEXT:   liveins: $vgpr0, $sgpr4_sgpr5, $sgpr6_sgpr7, $sgpr8_sgpr9, $sgpr10_sgpr11, $sgpr14, $sgpr15, $sgpr16
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[DEF:%[0-9]+]]:sreg_64_xexec = IMPLICIT_DEF
+  ; CHECK-NEXT:   undef %1.sub1:vreg_64 = V_CNDMASK_B32_e64 0, 0, 0, 1, [[DEF]], implicit $exec
+  ; CHECK-NEXT:   [[V_CMP_GT_I32_e64_:%[0-9]+]]:sreg_64 = V_CMP_GT_I32_e64 0, %1.sub1, implicit $exec
+  ; CHECK-NEXT:   %1.sub0:vreg_64 = V_MOV_B32_e32 123, implicit $exec
+  ; CHECK-NEXT:   $exec = S_MOV_B64_term [[V_CMP_GT_I32_e64_]]
+  ; CHECK-NEXT:   S_CBRANCH_EXECZ %bb.2, implicit $exec
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.1:
+  ; CHECK-NEXT:   successors: %bb.3(0x40000000), %bb.2(0x40000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   $vcc = S_ANDN2_B64 $exec, [[DEF]], implicit-def dead $scc
+  ; CHECK-NEXT:   S_CBRANCH_VCCNZ %bb.3, implicit $vcc
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.2:
+  ; CHECK-NEXT:   successors: %bb.3(0x80000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   S_NOP 0, implicit %1.sub0
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.3:
+  bb.0:
+    liveins: $vgpr0, $sgpr4_sgpr5, $sgpr6_sgpr7, $sgpr8_sgpr9, $sgpr10_sgpr11, $sgpr14, $sgpr15, $sgpr16
+
+    %0:sreg_64_xexec = IMPLICIT_DEF
+    undef %1.sub1:vreg_64 = V_CNDMASK_B32_e64 0, 0, 0, 1, %0, implicit $exec
+    %1.sub0 = V_MOV_B32_e32 123, implicit $exec
+    %2:sreg_64 = V_CMP_GT_I32_e64 0, %1.sub1, implicit $exec
+    $exec = S_MOV_B64_term %2
+    S_CBRANCH_EXECZ %bb.2, implicit $exec
+
+  bb.1:
+    %3:sreg_64_xexec = V_CMP_NE_U32_e64 1, %1.sub1, implicit $exec
+    $vcc = S_AND_B64 $exec, %3, implicit-def dead $scc
+    S_CBRANCH_VCCNZ %bb.3, implicit killed $vcc
+
+  bb.2:
+    S_NOP 0, implicit %1.sub0
+
+  bb.3:
+
+...