TableGen/GlobalISel: Handle non-leaf EXTRACT_SUBREG

This previously only handled EXTRACT_SUBREGs from leafs, such as operands directly in the original output. Handle extracting from a result instruction.
2025-01-31 12:41:49 +01:00 · 2020-01-14 16:02:02 -05:00 · 2020-01-14 16:02:02 -05:00 · 653b9c5a80
commit 653b9c5a80
parent a3296c73e9
9 changed files with 187 additions and 68 deletions
--- a/include/llvm/CodeGen/GlobalISel/InstructionSelector.h
+++ b/include/llvm/CodeGen/GlobalISel/InstructionSelector.h
@ -293,6 +293,13 @@ enum {
  /// - TempRegFlags - The register flags to set
  GIR_AddTempRegister,

+  /// Add a temporary register to the specified instruction
+  /// - InsnID - Instruction ID to modify
+  /// - TempRegID - The temporary register ID to add
+  /// - TempRegFlags - The register flags to set
+  /// - SubRegIndex - The subregister index to set
+  GIR_AddTempSubRegister,
+
  /// Add an immediate to the specified instruction
  /// - InsnID - Instruction ID to modify
  /// - Imm - The immediate to add
--- a/include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h
+++ b/include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h
@ -859,16 +859,25 @@ bool InstructionSelector::executeMatchTable(
      break;
    }

-    case GIR_AddTempRegister: {
+    case GIR_AddTempRegister:
+    case GIR_AddTempSubRegister: {
      int64_t InsnID = MatchTable[CurrentIdx++];
      int64_t TempRegID = MatchTable[CurrentIdx++];
      uint64_t TempRegFlags = MatchTable[CurrentIdx++];
+      unsigned SubReg = 0;
+      if (MatcherOpcode == GIR_AddTempSubRegister)
+        SubReg = MatchTable[CurrentIdx++];
+
      assert(OutMIs[InsnID] && "Attempted to add to undefined instruction");
-      OutMIs[InsnID].addReg(State.TempRegisters[TempRegID], TempRegFlags);
+
+      OutMIs[InsnID].addReg(State.TempRegisters[TempRegID], TempRegFlags, SubReg);
      DEBUG_WITH_TYPE(TgtInstructionSelector::getName(),
                      dbgs() << CurrentIdx << ": GIR_AddTempRegister(OutMIs["
                             << InsnID << "], TempRegisters[" << TempRegID
-                             << "], " << TempRegFlags << ")\n");
+                             << "]";
+                      if (SubReg)
+                        dbgs() << '.' << TRI.getSubRegIndexName(SubReg);
+                      dbgs() << ", " << TempRegFlags << ")\n");
      break;
    }

--- a/test/CodeGen/X86/GlobalISel/select-copy.mir
+++ b/test/CodeGen/X86/GlobalISel/select-copy.mir
@ -88,7 +88,8 @@ legalized:       true
 regBankSelected: true
 # ALL:      registers:
 # ALL-NEXT:   - { id: 0, class: gr16[[ABCD:(_abcd)?]], preferred-register: '' }
-# ALL-NEXT:   - { id: 1, class: gr8, preferred-register: '' }
+# X32-NEXT:   - { id: 1, class: gr8_abcd_l, preferred-register: '' }
+# X64-NEXT:   - { id: 1, class: gr8, preferred-register: '' }
 # ALL-NEXT:   - { id: 2, class: gr32, preferred-register: '' }
 registers:
  - { id: 0, class: gpr, preferred-register: '' }
@ -148,7 +149,8 @@ legalized:       true
 regBankSelected: true
 # ALL:      registers:
 # ALL-NEXT:   - { id: 0, class: gr32[[ABCD:(_abcd)?]], preferred-register: '' }
-# ALL-NEXT:   - { id: 1, class: gr8, preferred-register: '' }
+# X32-NEXT:   - { id: 1, class: gr8_abcd_l, preferred-register: '' }
+# X64-NEXT:   - { id: 1, class: gr8, preferred-register: '' }
 # ALL-NEXT:   - { id: 2, class: gr32, preferred-register: '' }
 registers:
  - { id: 0, class: gpr, preferred-register: '' }
--- a/test/CodeGen/X86/GlobalISel/select-ext.mir
+++ b/test/CodeGen/X86/GlobalISel/select-ext.mir
@ -374,8 +374,8 @@ alignment:       16
 legalized:       true
 regBankSelected: true
 # X32:      registers:
-# X32-NEXT:   - { id: 0, class: gr32_abcd, preferred-register: '' }
-# X32-NEXT:   - { id: 1, class: gr8, preferred-register: '' }
+# X32-NEXT:   - { id: 0, class: gr32, preferred-register: '' }
+# X32-NEXT:   - { id: 1, class: gr8_abcd_l, preferred-register: '' }
 # X32-NEXT:   - { id: 2, class: gr16, preferred-register: '' }
 #
 # X64:      registers:
@ -386,10 +386,15 @@ registers:
  - { id: 0, class: gpr }
  - { id: 1, class: gpr }
  - { id: 2, class: gpr }
-# X32:          %0:gr32_abcd = COPY $edi
-# X64:          %0:gr32 = COPY $edi
-# ALL-NEXT:     %1:gr8 = COPY %0.sub_8bit
-# ALL-NEXT:     %2:gr16 = SUBREG_TO_REG 0, %1, %subreg.sub_8bit
+# X32:          %0:gr32 = COPY $edi
+# X32-NEXT:    %4:gr32_abcd = COPY %0
+# X32-NEXT:     %1:gr8_abcd_l = COPY %4.sub_8bit
+
+# X64:               %0:gr32 = COPY $edi
+# X64-NEXT:     %1:gr8 = COPY %0.sub_8bit
+
+# ALL-NEXT:     %3:gr32 = MOVZX32rr8 %1
+# ALL-NEXT:     %2:gr16 = COPY %3.sub_16bit
 # ALL-NEXT:     $ax = COPY %2
 # ALL-NEXT:     RET 0, implicit $ax
 body:             |
@ -409,8 +414,8 @@ alignment:       16
 legalized:       true
 regBankSelected: true
 # X32:      registers:
-# X32-NEXT:   - { id: 0, class: gr32_abcd, preferred-register: '' }
-# X32-NEXT:   - { id: 1, class: gr8, preferred-register: '' }
+# X32-NEXT:   - { id: 0, class: gr32, preferred-register: '' }
+# X32-NEXT:   - { id: 1, class: gr8_abcd_l, preferred-register: '' }
 # X32-NEXT:   - { id: 2, class: gr32, preferred-register: '' }
 #
 # X64:      registers:
@ -421,9 +426,13 @@ registers:
  - { id: 0, class: gpr }
  - { id: 1, class: gpr }
  - { id: 2, class: gpr }
-# X32:          %0:gr32_abcd = COPY $edi
+# X32:          %0:gr32 = COPY $edi
+# X32-NEXT: %3:gr32_abcd = COPY %0
+# X32-NEXT: %1:gr8_abcd_l = COPY %3.sub_8bit
+
 # X64:          %0:gr32 = COPY $edi
-# ALL-NEXT:     %1:gr8 = COPY %0.sub_8bit
+# X64-NEXT: %1:gr8 = COPY %0.sub_8bit
+
 # ALL-NEXT:     %2:gr32 = MOVZX32rr8 %1
 # ALL-NEXT:     $eax = COPY %2
 # ALL-NEXT:     RET 0, implicit $eax
--- a/test/CodeGen/X86/GlobalISel/shl-scalar-widening.ll
+++ b/test/CodeGen/X86/GlobalISel/shl-scalar-widening.ll
@ -10,13 +10,13 @@ define i16 @test_shl_i4(i16 %v, i16 %a, i16 %b) {
 ; %b: 72 (0000 0000  0100 1000)
 ; X64-LABEL: test_shl_i4:
 ; X64:       # %bb.0:
-; X64-NEXT:    movl %edi, %eax
 ; X64-NEXT:    # kill: def $esi killed $esi def $rsi
 ; X64-NEXT:    # kill: def $edx killed $edx def $rdx
 ; X64-NEXT:    leal (%rdx,%rsi), %ecx
 ; X64-NEXT:    andb $15, %cl
 ; X64-NEXT:    # kill: def $cl killed $cl killed $ecx
-; X64-NEXT:    shlb %cl, %al
+; X64-NEXT:    shlb %cl, %dil
+; X64-NEXT:    movzbl %dil, %eax
 ; X64-NEXT:    andw $15, %ax
 ; X64-NEXT:    # kill: def $ax killed $ax killed $eax
 ; X64-NEXT:    retq
--- a/test/CodeGen/X86/GlobalISel/x86-select-sdiv.mir
+++ b/test/CodeGen/X86/GlobalISel/x86-select-sdiv.mir
@ -40,14 +40,16 @@ body:             |

    ; CHECK-LABEL: name: test_sdiv_i8
    ; CHECK: liveins: $edi, $esi
-    ; CHECK: [[COPY:%[0-9]+]]:gr32_abcd = COPY $edi
-    ; CHECK: [[COPY1:%[0-9]+]]:gr8 = COPY [[COPY]].sub_8bit
-    ; CHECK: [[COPY2:%[0-9]+]]:gr32_abcd = COPY $esi
-    ; CHECK: [[COPY3:%[0-9]+]]:gr8 = COPY [[COPY2]].sub_8bit
-    ; CHECK: $ax = MOVSX16rr8 [[COPY1]]
-    ; CHECK: IDIV8r [[COPY3]], implicit-def $al, implicit-def $ah, implicit-def $eflags, implicit $ax
-    ; CHECK: [[COPY4:%[0-9]+]]:gr8 = COPY $al
-    ; CHECK: $al = COPY [[COPY4]]
+    ; CHECK: [[COPY:%[0-9]+]]:gr32 = COPY $edi
+    ; CHECK: [[COPY1:%[0-9]+]]:gr32_abcd = COPY [[COPY]]
+    ; CHECK: [[COPY2:%[0-9]+]]:gr8_abcd_l = COPY [[COPY1]].sub_8bit
+    ; CHECK: [[COPY3:%[0-9]+]]:gr32 = COPY $esi
+    ; CHECK: [[COPY4:%[0-9]+]]:gr32_abcd = COPY [[COPY3]]
+    ; CHECK: [[COPY5:%[0-9]+]]:gr8_abcd_l = COPY [[COPY4]].sub_8bit
+    ; CHECK: $ax = MOVSX16rr8 [[COPY2]]
+    ; CHECK: IDIV8r [[COPY5]], implicit-def $al, implicit-def $ah, implicit-def $eflags, implicit $ax
+    ; CHECK: [[COPY6:%[0-9]+]]:gr8 = COPY $al
+    ; CHECK: $al = COPY [[COPY6]]
    ; CHECK: RET 0, implicit $al
    %2:gpr(s32) = COPY $edi
    %0:gpr(s8) = G_TRUNC %2(s32)
--- a/test/CodeGen/X86/GlobalISel/x86_64-select-zext.mir
+++ b/test/CodeGen/X86/GlobalISel/x86_64-select-zext.mir
@ -198,8 +198,10 @@ body:             |
    ; CHECK: liveins: $edi
    ; CHECK: [[COPY:%[0-9]+]]:gr32 = COPY $edi
    ; CHECK: [[COPY1:%[0-9]+]]:gr16 = COPY [[COPY]].sub_16bit
-    ; CHECK: [[AND16ri:%[0-9]+]]:gr16 = AND16ri [[COPY1]], 255, implicit-def $eflags
-    ; CHECK: $ax = COPY [[AND16ri]]
+    ; CHECK: [[COPY2:%[0-9]+]]:gr8 = COPY [[COPY1]].sub_8bit
+    ; CHECK: [[MOVZX32rr8_:%[0-9]+]]:gr32 = MOVZX32rr8 [[COPY2]]
+    ; CHECK: [[COPY3:%[0-9]+]]:gr16 = COPY [[MOVZX32rr8_]].sub_16bit
+    ; CHECK: $ax = COPY [[COPY3]]
    ; CHECK: RET 0, implicit $ax
    %1:gpr(s32) = COPY $edi
    %3:gpr(s16) = G_CONSTANT i16 255
--- a/test/TableGen/GlobalISelEmitterSubreg.td
+++ b/test/TableGen/GlobalISelEmitterSubreg.td
@ -34,6 +34,7 @@ def SOP : RegisterOperand<SRegs>;
 def DOP : RegisterOperand<DRegs>;
 def SOME_INSN : I<(outs DRegs:$dst), (ins DOP:$src), []>;
 def SUBSOME_INSN : I<(outs SRegs:$dst), (ins SOP:$src), []>;
+def SUBSOME_INSN2 : I<(outs SRegs:$dst), (ins SOP:$src), []>;

 // We should skip cases where we don't have a given register class for the
 // subregister source.
@ -132,6 +133,52 @@ def : Pat<(i16 (trunc (not DOP:$src))),
 // CHECK-NEXT: GIR_ConstrainOperandRC, /*InsnID*/1, /*Op*/1, /*RC DRegs*/1,
 // CHECK-NEXT: GIR_BuildMI, /*InsnID*/0, /*Opcode*/MyTarget::SUBSOME_INSN,

+// Test an extract from an output instruction result (nonleaf)
+def : Pat<(i16 (trunc (bitreverse DOP:$src))),
+           (EXTRACT_SUBREG (SOME_INSN DOP:$src), sub0)>;
+// CHECK-LABEL: GIM_CheckOpcode, /*MI*/1, TargetOpcode::G_BITREVERSE,
+// CHECK-NEXT:  GIM_CheckType, /*MI*/1, /*Op*/1, /*Type*/GILLT_s32,
+// CHECK-NEXT:  GIM_CheckRegBankForClass, /*MI*/1, /*Op*/1, /*RC*/Test::DRegsRegClassID,
+// CHECK-NEXT:  GIM_CheckIsSafeToFold, /*InsnID*/1,
+// CHECK-NEXT:  // (trunc:{ *:[i16] } (bitreverse:{ *:[i32] } DOP:{ *:[i32] }:$src))  =>  (EXTRACT_SUBREG:{ *:[i16] } (SOME_INSN:{ *:[i32] } DOP:{ *:[i32] }:$src), sub0:{ *:[i32] })
+// CHECK-NEXT:  GIR_MakeTempReg, /*TempRegID*/0, /*TypeID*/GILLT_s32,
+// CHECK-NEXT:  GIR_BuildMI, /*InsnID*/1, /*Opcode*/MyTarget::SOME_INSN,
+// CHECK-NEXT:  GIR_AddTempRegister, /*InsnID*/1, /*TempRegID*/0, /*TempRegFlags*/RegState::Define,
+// CHECK-NEXT:  GIR_Copy, /*NewInsnID*/1, /*OldInsnID*/1, /*OpIdx*/1, // src
+// CHECK-NEXT:  GIR_ConstrainSelectedInstOperands, /*InsnID*/1,
+// CHECK-NEXT:  GIR_BuildMI, /*InsnID*/0, /*Opcode*/TargetOpcode::COPY,
+// CHECK-NEXT:  GIR_Copy, /*NewInsnID*/0, /*OldInsnID*/0, /*OpIdx*/0, // dst
+// CHECK-NEXT:  GIR_AddTempSubRegister, /*InsnID*/0, /*TempRegID*/0, /*TempRegFlags*/0, sub0,
+// CHECK-NEXT:  GIR_EraseFromParent, /*InsnID*/0,
+// CHECK-NEXT:  GIR_ConstrainOperandRC, /*InsnID*/0, /*Op*/0, /*RC SRegs*/0,
+// CHECK-NEXT:  GIR_ConstrainOperandRC, /*InsnID*/0, /*Op*/1, /*RC DRegs*/1,
+
+// EXTRACT_SUBREG is subinstruction, but also doesn't have a leaf input
+
+// CHECK-LABEL: GIM_CheckOpcode, /*MI*/1, TargetOpcode::G_CTPOP,
+// CHECK-NEXT: GIM_CheckType, /*MI*/1, /*Op*/1, /*Type*/GILLT_s32,
+// CHECK-NEXT: GIM_CheckRegBankForClass, /*MI*/1, /*Op*/1, /*RC*/Test::DRegsRegClassID,
+// CHECK-NEXT: GIM_CheckIsSafeToFold, /*InsnID*/1,
+// CHECK-NEXT: // (trunc:{ *:[i16] } (ctpop:{ *:[i32] } DOP:{ *:[i32] }:$src))  =>  (SUBSOME_INSN2:{ *:[i16] } (EXTRACT_SUBREG:{ *:[i16] } (SOME_INSN:{ *:[i32] } DOP:{ *:[i32] }:$src), sub0:{ *:[i32] }))
+// CHECK-NEXT: GIR_MakeTempReg, /*TempRegID*/0, /*TypeID*/GILLT_s16,
+// CHECK-NEXT: GIR_MakeTempReg, /*TempRegID*/1, /*TypeID*/GILLT_s32,
+// CHECK-NEXT: GIR_BuildMI, /*InsnID*/2, /*Opcode*/MyTarget::SOME_INSN,
+// CHECK-NEXT: GIR_AddTempRegister, /*InsnID*/2, /*TempRegID*/1, /*TempRegFlags*/RegState::Define,
+// CHECK-NEXT: GIR_Copy, /*NewInsnID*/2, /*OldInsnID*/1, /*OpIdx*/1, // src
+// CHECK-NEXT: GIR_ConstrainSelectedInstOperands, /*InsnID*/2,
+// CHECK-NEXT: GIR_BuildMI, /*InsnID*/1, /*Opcode*/TargetOpcode::COPY,
+// CHECK-NEXT: GIR_AddTempRegister, /*InsnID*/1, /*TempRegID*/0, /*TempRegFlags*/RegState::Define,
+// CHECK-NEXT: GIR_AddTempSubRegister, /*InsnID*/1, /*TempRegID*/1, /*TempRegFlags*/0, sub0,
+// CHECK-NEXT: GIR_ConstrainOperandRC, /*InsnID*/1, /*Op*/0, /*RC SRegs*/0,
+// CHECK-NEXT: GIR_ConstrainOperandRC, /*InsnID*/1, /*Op*/1, /*RC DRegs*/1,
+// CHECK-NEXT: GIR_BuildMI, /*InsnID*/0, /*Opcode*/MyTarget::SUBSOME_INSN2,
+// CHECK-NEXT: GIR_Copy, /*NewInsnID*/0, /*OldInsnID*/0, /*OpIdx*/0, // dst
+// CHECK-NEXT: GIR_AddTempRegister, /*InsnID*/0, /*TempRegID*/0, /*TempRegFlags*/0,
+// CHECK-NEXT: GIR_EraseFromParent, /*InsnID*/0,
+// CHECK-NEXT: GIR_ConstrainSelectedInstOperands, /*InsnID*/0,
+def : Pat<(i16 (trunc (ctpop DOP:$src))),
+           (SUBSOME_INSN2 (EXTRACT_SUBREG (SOME_INSN DOP:$src), sub0))>;
+
 // Test an EXTRACT_SUBREG that is the final instruction.
 def : Pat<(i16 (trunc DOP:$src)),
           (EXTRACT_SUBREG DOP:$src, sub0)>;
--- a/utils/TableGen/GlobalISelEmitter.cpp
+++ b/utils/TableGen/GlobalISelEmitter.cpp
@ -2585,26 +2585,37 @@ class TempRegRenderer : public OperandRenderer {
 protected:
  unsigned InsnID;
  unsigned TempRegID;
+  const CodeGenSubRegIndex *SubRegIdx;
  bool IsDef;

 public:
-  TempRegRenderer(unsigned InsnID, unsigned TempRegID, bool IsDef = false)
+  TempRegRenderer(unsigned InsnID, unsigned TempRegID, bool IsDef = false,
+                  const CodeGenSubRegIndex *SubReg = nullptr)
      : OperandRenderer(OR_Register), InsnID(InsnID), TempRegID(TempRegID),
-        IsDef(IsDef) {}
+        SubRegIdx(SubReg), IsDef(IsDef) {}

  static bool classof(const OperandRenderer *R) {
    return R->getKind() == OR_TempRegister;
  }

  void emitRenderOpcodes(MatchTable &Table, RuleMatcher &Rule) const override {
-    Table << MatchTable::Opcode("GIR_AddTempRegister")
-          << MatchTable::Comment("InsnID") << MatchTable::IntValue(InsnID)
+    if (SubRegIdx) {
+      assert(!IsDef);
+      Table << MatchTable::Opcode("GIR_AddTempSubRegister");
+    } else
+      Table << MatchTable::Opcode("GIR_AddTempRegister");
+
+    Table << MatchTable::Comment("InsnID") << MatchTable::IntValue(InsnID)
          << MatchTable::Comment("TempRegID") << MatchTable::IntValue(TempRegID)
          << MatchTable::Comment("TempRegFlags");
+
    if (IsDef)
      Table << MatchTable::NamedValue("RegState::Define");
    else
      Table << MatchTable::IntValue(0);
+
+    if (SubRegIdx)
+      Table << MatchTable::NamedValue(SubRegIdx->getQualifiedName());
    Table << MatchTable::LineBreak;
  }
 };
@ -3260,6 +3271,22 @@ void SameOperandMatcher::emitPredicateOpcodes(MatchTable &Table,

 //===- GlobalISelEmitter class --------------------------------------------===//

+static Expected<LLTCodeGen> getInstResultType(const TreePatternNode *Dst) {
+  ArrayRef<TypeSetByHwMode> ChildTypes = Dst->getExtTypes();
+  if (ChildTypes.size() != 1)
+    return failedImport("Dst pattern child has multiple results");
+
+  Optional<LLTCodeGen> MaybeOpTy;
+  if (ChildTypes.front().isMachineValueType()) {
+    MaybeOpTy =
+      MVTToLLT(ChildTypes.front().getMachineValueType().SimpleTy);
+  }
+
+  if (!MaybeOpTy)
+    return failedImport("Dst operand has an unsupported type");
+  return *MaybeOpTy;
+}
+
 class GlobalISelEmitter {
 public:
  explicit GlobalISelEmitter(RecordKeeper &RK);
@ -4044,20 +4071,13 @@ Expected<action_iterator> GlobalISelEmitter::importExplicitUseRenderer(
    }

    if (DstChild->getOperator()->isSubClassOf("Instruction")) {
-      ArrayRef<TypeSetByHwMode> ChildTypes = DstChild->getExtTypes();
-      if (ChildTypes.size() != 1)
-        return failedImport("Dst pattern child has multiple results");
-
-      Optional<LLTCodeGen> OpTyOrNone = None;
-      if (ChildTypes.front().isMachineValueType())
-        OpTyOrNone =
-            MVTToLLT(ChildTypes.front().getMachineValueType().SimpleTy);
-      if (!OpTyOrNone)
-        return failedImport("Dst operand has an unsupported type");
+      auto OpTy = getInstResultType(DstChild);
+      if (!OpTy)
+        return OpTy.takeError();

      unsigned TempRegID = Rule.allocateTempRegID();
      InsertPt = Rule.insertAction<MakeTempRegisterAction>(
-          InsertPt, OpTyOrNone.getValue(), TempRegID);
+          InsertPt, *OpTy, TempRegID);
      DstMIBuilder.addRenderer<TempRegRenderer>(TempRegID);

      auto InsertPtOrError = createAndImportSubInstructionRenderer(
@ -4307,33 +4327,51 @@ Expected<action_iterator> GlobalISelEmitter::importExplicitUseRenderers(

  // EXTRACT_SUBREG needs to use a subregister COPY.
  if (Name == "EXTRACT_SUBREG") {
-    if (!Dst->getChild(0)->isLeaf())
-      return failedImport("EXTRACT_SUBREG child #1 is not a leaf");
+    DefInit *SubRegInit = dyn_cast<DefInit>(Dst->getChild(1)->getLeafValue());
+    if (!SubRegInit)
+      return failedImport("EXTRACT_SUBREG child #1 is not a subreg index");

-    if (DefInit *SubRegInit =
-            dyn_cast<DefInit>(Dst->getChild(1)->getLeafValue())) {
-      Record *RCDef = getInitValueAsRegClass(Dst->getChild(0)->getLeafValue());
-      if (!RCDef)
-        return failedImport("EXTRACT_SUBREG child #0 could not "
-                            "be coerced to a register class");
+    CodeGenSubRegIndex *SubIdx = CGRegs.getSubRegIdx(SubRegInit->getDef());
+    TreePatternNode *ValChild = Dst->getChild(0);
+    if (!ValChild->isLeaf()) {
+      // We really have to handle the source instruction, and then insert a
+      // copy from the subregister.
+      auto ExtractSrcTy = getInstResultType(ValChild);
+      if (!ExtractSrcTy)
+        return ExtractSrcTy.takeError();

-      CodeGenRegisterClass *RC = CGRegs.getRegClass(RCDef);
-      CodeGenSubRegIndex *SubIdx = CGRegs.getSubRegIdx(SubRegInit->getDef());
+      unsigned TempRegID = M.allocateTempRegID();
+      InsertPt = M.insertAction<MakeTempRegisterAction>(
+        InsertPt, *ExtractSrcTy, TempRegID);

-      const auto SrcRCDstRCPair =
-          RC->getMatchingSubClassWithSubRegs(CGRegs, SubIdx);
-      if (SrcRCDstRCPair.hasValue()) {
-        assert(SrcRCDstRCPair->second && "Couldn't find a matching subclass");
-        if (SrcRCDstRCPair->first != RC)
-          return failedImport("EXTRACT_SUBREG requires an additional COPY");
-      }
+      auto InsertPtOrError = createAndImportSubInstructionRenderer(
+        ++InsertPt, M, ValChild, TempRegID);
+      if (auto Error = InsertPtOrError.takeError())
+        return std::move(Error);

-      DstMIBuilder.addRenderer<CopySubRegRenderer>(Dst->getChild(0)->getName(),
-                                                   SubIdx);
+      DstMIBuilder.addRenderer<TempRegRenderer>(TempRegID, false, SubIdx);
      return InsertPt;
    }

-    return failedImport("EXTRACT_SUBREG child #1 is not a subreg index");
+    // If this is a source operand, this is just a subregister copy.
+    Record *RCDef = getInitValueAsRegClass(ValChild->getLeafValue());
+    if (!RCDef)
+      return failedImport("EXTRACT_SUBREG child #0 could not "
+                          "be coerced to a register class");
+
+    CodeGenRegisterClass *RC = CGRegs.getRegClass(RCDef);
+
+    const auto SrcRCDstRCPair =
+      RC->getMatchingSubClassWithSubRegs(CGRegs, SubIdx);
+    if (SrcRCDstRCPair.hasValue()) {
+      assert(SrcRCDstRCPair->second && "Couldn't find a matching subclass");
+      if (SrcRCDstRCPair->first != RC)
+        return failedImport("EXTRACT_SUBREG requires an additional COPY");
+    }
+
+    DstMIBuilder.addRenderer<CopySubRegRenderer>(Dst->getChild(0)->getName(),
+                                                 SubIdx);
+    return InsertPt;
  }

  if (Name == "REG_SEQUENCE") {
@ -4735,15 +4773,13 @@ Expected<RuleMatcher> GlobalISelEmitter::runOnPattern(const PatternToMatch &P) {
      if (DstIOpRec == nullptr)
        return failedImport("REG_SEQUENCE operand #0 isn't a register class");
    } else if (DstIName == "EXTRACT_SUBREG") {
-      if (!Dst->getChild(0)->isLeaf())
-        return failedImport("EXTRACT_SUBREG operand #0 isn't a leaf");
+      auto InferredClass = inferRegClassFromPattern(Dst->getChild(0));
+      if (!InferredClass)
+        return failedImport("Could not infer class for EXTRACT_SUBREG operand #0");

      // We can assume that a subregister is in the same bank as it's super
      // register.
-      DstIOpRec = getInitValueAsRegClass(Dst->getChild(0)->getLeafValue());
-
-      if (DstIOpRec == nullptr)
-        return failedImport("EXTRACT_SUBREG operand #0 isn't a register class");
+      DstIOpRec = (*InferredClass)->getDef();
    } else if (DstIName == "INSERT_SUBREG") {
      auto MaybeSuperClass = inferSuperRegisterClassForNode(
          VTy, Dst->getChild(0), Dst->getChild(2));
@ -4838,6 +4874,11 @@ Expected<RuleMatcher> GlobalISelEmitter::runOnPattern(const PatternToMatch &P) {

    const auto SrcRCDstRCPair =
      (*SuperClass)->getMatchingSubClassWithSubRegs(CGRegs, *SubIdx);
+    if (!SrcRCDstRCPair) {
+      return failedImport("subreg index is incompatible "
+                          "with inferred reg class");
+    }
+
    assert(SrcRCDstRCPair->second && "Couldn't find a matching subclass");
    M.addAction<ConstrainOperandToRegClassAction>(0, 0, *SrcRCDstRCPair->second);
    M.addAction<ConstrainOperandToRegClassAction>(0, 1, *SrcRCDstRCPair->first);