AMDGPU/GlobalISel: Fix G_EXTRACT of 96-bit results

[arsenm]

Summary

This would assert on an unhandled size in getRegSplitParts.

[arsenm]

ping

[kerbowa]

LGTM. Just ran into the same issue.

[arsenm]

dc3e499dd4a6bd0882ca0af453cea99620320ffe

llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp

if (HasCarryIn &&
       !RBI.constrainGenericRegister(I.getOperand(4).getReg(),
                                     AMDGPU::SReg_32RegClass, *MRI))
     return false;
 
   I.eraseFromParent();
   return true;
 }
 
+// TODO: We should probably legalize these to only using 32-bit results.
 bool AMDGPUInstructionSelector::selectG_EXTRACT(MachineInstr &I) const {
   MachineBasicBlock *BB = I.getParent();
   Register DstReg = I.getOperand(0).getReg();
   Register SrcReg = I.getOperand(1).getReg();
   LLT DstTy = MRI->getType(DstReg);
   LLT SrcTy = MRI->getType(SrcReg);
   const unsigned SrcSize = SrcTy.getSizeInBits();
   const unsigned DstSize = DstTy.getSizeInBits();
 
   // TODO: Should handle any multiple of 32 offset.
   unsigned Offset = I.getOperand(2).getImm();
-  if (Offset % DstSize != 0)
+  if (Offset % 32 != 0 || DstSize > 128)
+    return false;
+
+  const TargetRegisterClass *DstRC =
+    TRI.getConstrainedRegClassForOperand(I.getOperand(0), *MRI);
+  if (!DstRC || !RBI.constrainGenericRegister(DstReg, *DstRC, *MRI))
     return false;
 
   const RegisterBank *SrcBank = RBI.getRegBank(SrcReg, *MRI, TRI);
   const TargetRegisterClass *SrcRC =
     TRI.getRegClassForSizeOnBank(SrcSize, *SrcBank, *MRI);
   if (!SrcRC)
     return false;
+  unsigned SubReg = AMDGPURegisterInfo::getSubRegFromChannel(Offset / 32,
+                                                             DstSize / 32);
+  SrcRC = TRI.getSubClassWithSubReg(SrcRC, SubReg);
+  if (!SrcRC)
+    return false;
 
-  ArrayRef<int16_t> SubRegs = TRI.getRegSplitParts(SrcRC, DstSize / 8);
-
+  SrcReg = constrainOperandRegClass(*MF, TRI, *MRI, TII, RBI, I,
+                                    *SrcRC, I.getOperand(1));
   const DebugLoc &DL = I.getDebugLoc();
-  MachineInstr *Copy = BuildMI(*BB, &I, DL, TII.get(TargetOpcode::COPY), DstReg)
-                               .addReg(SrcReg, 0, SubRegs[Offset / DstSize]);
+  BuildMI(*BB, &I, DL, TII.get(TargetOpcode::COPY), DstReg)
+    .addReg(SrcReg, 0, SubReg);
 
-  for (const MachineOperand &MO : Copy->operands()) {
-    const TargetRegisterClass *RC =
-            TRI.getConstrainedRegClassForOperand(MO, *MRI);
-    if (!RC)
-      continue;
-    RBI.constrainGenericRegister(MO.getReg(), *RC, *MRI);
-  }
   I.eraseFromParent();
   return true;
 }
 
 bool AMDGPUInstructionSelector::selectG_MERGE_VALUES(MachineInstr &MI) const {
   MachineBasicBlock *BB = MI.getParent();
   Register DstReg = MI.getOperand(0).getReg();
   LLT DstTy = MRI->getType(DstReg);

llvm/test/CodeGen/AMDGPU/GlobalISel/inst-select-extract.mir

bb.0:
     ; CHECK: [[COPY1:%[0-9]+]]:sreg_64 = COPY [[DEF]].sub2_sub3
     ; CHECK: S_ENDPGM 0, implicit [[COPY]], implicit [[COPY1]]
     %0:sgpr(s128) = G_IMPLICIT_DEF
     %1:sgpr(s64) = G_EXTRACT %0, 0
     %2:sgpr(s64) = G_EXTRACT %0, 64
     S_ENDPGM 0, implicit %1, implicit %2
 
 ...
+
+---
+name:            extract_sgpr_s96_from_s128
+legalized:       true
+regBankSelected: true
+
+body: |
+  bb.0:
+    liveins: $sgpr0_sgpr1_sgpr2_sgpr3
+    ; CHECK-LABEL: name: extract_sgpr_s96_from_s128
+    ; CHECK: [[COPY:%[0-9]+]]:sgpr_128_with_sub1_sub2_sub3 = COPY $sgpr0_sgpr1_sgpr2_sgpr3
+    ; CHECK: [[COPY1:%[0-9]+]]:sgpr_128_with_sub0_sub1_sub2 = COPY [[COPY]]
+    ; CHECK: [[COPY2:%[0-9]+]]:sreg_96 = COPY [[COPY1]].sub0_sub1_sub2
+    ; CHECK: [[COPY3:%[0-9]+]]:sreg_96 = COPY [[COPY]].sub1_sub2_sub3
+    ; CHECK: S_ENDPGM 0, implicit [[COPY2]], implicit [[COPY3]]
+    %0:sgpr(s128) = COPY $sgpr0_sgpr1_sgpr2_sgpr3
+    %1:sgpr(s96) = G_EXTRACT %0, 0
+    %2:sgpr(s96) = G_EXTRACT %0, 32
+    S_ENDPGM 0, implicit %1, implicit %2
+
+...
+
+---
+name:            extract_sgpr_v3s32_from_v4s32
+legalized:       true
+regBankSelected: true
+
+body: |
+  bb.0:
+    liveins: $sgpr0_sgpr1_sgpr2_sgpr3
+    ; CHECK-LABEL: name: extract_sgpr_v3s32_from_v4s32
+    ; CHECK: [[COPY:%[0-9]+]]:sgpr_128_with_sub1_sub2_sub3 = COPY $sgpr0_sgpr1_sgpr2_sgpr3
+    ; CHECK: [[COPY1:%[0-9]+]]:sgpr_128_with_sub0_sub1_sub2 = COPY [[COPY]]
+    ; CHECK: [[COPY2:%[0-9]+]]:sreg_96 = COPY [[COPY1]].sub0_sub1_sub2
+    ; CHECK: [[COPY3:%[0-9]+]]:sreg_96 = COPY [[COPY]].sub1_sub2_sub3
+    ; CHECK: S_ENDPGM 0, implicit [[COPY2]], implicit [[COPY3]]
+    %0:sgpr(<4 x s32>) = COPY $sgpr0_sgpr1_sgpr2_sgpr3
+    %1:sgpr(<3 x s32>) = G_EXTRACT %0, 0
+    %2:sgpr(<3 x s32>) = G_EXTRACT %0, 32
+    S_ENDPGM 0, implicit %1, implicit %2
+
+...