[GlobalISel] Import patterns containing INSERT_SUBREG

[paquette]

Summary

This teaches the importer to handle INSERT_SUBREG instructions. We were missing patterns involving INSERT_SUBREG in AArch64.

To meaningfully import it, the GlobalISelEmitter needs to know how to infer a super register class for a given register class.

This patch introduces the following to achieve this:

• getSuperRegForSubReg, a function which finds the largest register class which supports a value type and subregister index
• inferSuperRegisterClass, a function which finds the appropriate super register class for an INSERT_SUBREG
• inferRegClassFromPattern, a function which allows for some trivial lookthrough into instructions
• getRegClassFromLeaf, a helper function which returns the register class for a leaf TreePatternNode
• Support for subregister index operands in importExplicitUseRenderer

It also

• Updates tests in each backend which are impacted by the change
• Adds GlobalISelEmitterSubreg.td to test that we import and skip the expected patterns

As a result of this patch, INSERT_SUBREG patterns in X86 may use the LOW32_ADDR_ACCESS_RBP register class instead of GR32. This is correct, since the register class contains the same registers as GR32 (except with the addition of RBP). So, this also teaches X86 to handle that register class. This is in line with X86ISelLowering, which treats this as a GR class.

[aemerson]

llvm/utils/TableGen/GlobalISelEmitter.cpp

4149

getSuperRegForSubReg() seems to return an Optional, but here you get the value without checking if it's None.

[paquette]

• Check for None in inferSuperRegisterClass.

• Rename test to GlobalISelEmitterSubreg.td. I have some changes that implement SUBREG_TO_REG and I decided to reuse the test for it, so might as well do the rename here.

• Remove unused flag from FileCheck line in the test.

[aemerson]

LGTM.

[RKSimon]

@paquette This is causing failures on EXPENSIVE_CHECKS builds, please can you take a look?

http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-win/builds/19367
http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-win/builds/19367/steps/test-check-all/logs/stdio

[paquette]

@RKSimon, I'm trying to reproduce the test failures locally without much luck right now. For me, with EXPENSIVE_CHECKS enabled, the modified tests all pass.

Do the Windows builders build -mtriple=aarch64-- differently?

As for the Tablegen test, it looks like it's not redirecting the output properly on Windows.

[paquette]

After a bit of digging, it looks like we're not actually getting stable output here when the match tables are optimized. If they aren't optimized, it's stable.

Going to back this out and recommit once I figure out what's going on.

[paquette]

For some reason, I thought llvm::sort was stable. So, what was happening is that sometimes you would end up with different register classes in getSuperRegForSubReg. As a result, when match tables are optimized, sometimes you would end up missing entire cases in the generated C++. (It would sometimes take a few tries to get it to fail, which is why I wasn't seeing it.)

Changing the llvm::sort to llvm::stable_sort fixes this on my end.

Recommitted in r370084. Hopefully this will make the bots happy. :)

[mgrang]

llvm/trunk/utils/TableGen/CodeGenTarget.cpp

330 ↗

(On Diff #217246)

If A and B have the same size then you would end up with a tie. This can result in non-deterministic sorting order. I guess you would need a tie breaker in that case.
See https://llvm.org/docs/CodingStandards.html#beware-of-non-deterministic-sorting-order-of-equal-elements.

[paquette]

llvm/trunk/utils/TableGen/CodeGenTarget.cpp

330 ↗

(On Diff #217246)

Yes, that was a bug. :) I switched it to llvm::stable_sort in r370084 to fix that. I think that's sufficient, and it's passing on the EXPENSIVE_CHECKS bots now as far as I can see.

(I believe that getRegClasses() is stable, so I think llvm::stable_sort should produce a deterministic result.)

llvm/lib/Target/X86/X86RegisterBankInfo.cpp

 }
 
 const RegisterBank &X86RegisterBankInfo::getRegBankFromRegClass(
     const TargetRegisterClass &RC) const {
 
   if (X86::GR8RegClass.hasSubClassEq(&RC) ||
       X86::GR16RegClass.hasSubClassEq(&RC) ||
       X86::GR32RegClass.hasSubClassEq(&RC) ||
-      X86::GR64RegClass.hasSubClassEq(&RC))
+      X86::GR64RegClass.hasSubClassEq(&RC) ||
+      X86::LOW32_ADDR_ACCESSRegClass.hasSubClassEq(&RC) ||
+      X86::LOW32_ADDR_ACCESS_RBPRegClass.hasSubClassEq(&RC))
     return getRegBank(X86::GPRRegBankID);
 
   if (X86::FR32XRegClass.hasSubClassEq(&RC) ||
       X86::FR64XRegClass.hasSubClassEq(&RC) ||
       X86::VR128XRegClass.hasSubClassEq(&RC) ||
       X86::VR256XRegClass.hasSubClassEq(&RC) ||
       X86::VR512RegClass.hasSubClassEq(&RC))
     return getRegBank(X86::VECRRegBankID);

llvm/test/CodeGen/AArch64/GlobalISel/select-concat-vectors.mir

 # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
 # RUN: llc -mtriple=aarch64-- -run-pass=instruction-select -verify-machineinstrs %s -o - | FileCheck %s
 ...
 ---
 name:            legal_v4s32_v2s32
 alignment:       2
 legalized:       true
 regBankSelected: true
+tracksRegLiveness: true
 registers:
   - { id: 0, class: fpr }
   - { id: 1, class: fpr }
   - { id: 2, class: fpr }
 frameInfo:
   maxCallFrameSize: 0
 body:             |
   bb.0:
+  liveins: $d0, $d1
     ; CHECK-LABEL: name: legal_v4s32_v2s32
+    ; CHECK: liveins: $d0, $d1
     ; CHECK: [[COPY:%[0-9]+]]:fpr64 = COPY $d0
     ; CHECK: [[COPY1:%[0-9]+]]:fpr64 = COPY $d1
     ; CHECK: [[DEF:%[0-9]+]]:fpr128 = IMPLICIT_DEF
-    ; CHECK: [[INSERT_SUBREG:%[0-9]+]]:fpr128 = INSERT_SUBREG [[DEF]], [[COPY]], %subreg.dsub
+    ; CHECK: [[INSERT_SUBREG:%[0-9]+]]:fpr128 = INSERT_SUBREG [[DEF]], [[COPY1]], %subreg.dsub
     ; CHECK: [[DEF1:%[0-9]+]]:fpr128 = IMPLICIT_DEF
-    ; CHECK: [[INSERT_SUBREG1:%[0-9]+]]:fpr128 = INSERT_SUBREG [[DEF1]], [[COPY1]], %subreg.dsub
-    ; CHECK: [[INSvi64lane:%[0-9]+]]:fpr128 = INSvi64lane [[INSERT_SUBREG]], 1, [[INSERT_SUBREG1]], 0
+    ; CHECK: [[INSERT_SUBREG1:%[0-9]+]]:fpr128 = INSERT_SUBREG [[DEF1]], [[COPY]], %subreg.dsub
+    ; CHECK: [[INSvi64lane:%[0-9]+]]:fpr128 = INSvi64lane [[INSERT_SUBREG1]], 1, [[INSERT_SUBREG]], 0
     ; CHECK: $q0 = COPY [[INSvi64lane]]
-    ; CHECK: RET_ReallyLR
+    ; CHECK: RET_ReallyLR implicit $q0
     %0:fpr(<2 x s32>) = COPY $d0
     %1:fpr(<2 x s32>) = COPY $d1
     %2:fpr(<4 x s32>) = G_CONCAT_VECTORS %0(<2 x s32>), %1(<2 x s32>)
     $q0 = COPY %2(<4 x s32>)
-    RET_ReallyLR
+    RET_ReallyLR implicit $q0
 
 ...
 ---
 name:            legal_v8s16_v4s16
 alignment:       2
 legalized:       true
 regBankSelected: true
+tracksRegLiveness: true
 registers:
   - { id: 0, class: fpr }
   - { id: 1, class: fpr }
   - { id: 2, class: fpr }
 frameInfo:
   maxCallFrameSize: 0
 body:             |
   bb.0:
+  liveins: $d0, $d1
     ; CHECK-LABEL: name: legal_v8s16_v4s16
+    ; CHECK: liveins: $d0, $d1
     ; CHECK: [[COPY:%[0-9]+]]:fpr64 = COPY $d0
     ; CHECK: [[COPY1:%[0-9]+]]:fpr64 = COPY $d1
     ; CHECK: [[DEF:%[0-9]+]]:fpr128 = IMPLICIT_DEF
-    ; CHECK: [[INSERT_SUBREG:%[0-9]+]]:fpr128 = INSERT_SUBREG [[DEF]], [[COPY]], %subreg.dsub
+    ; CHECK: [[INSERT_SUBREG:%[0-9]+]]:fpr128 = INSERT_SUBREG [[DEF]], [[COPY1]], %subreg.dsub
     ; CHECK: [[DEF1:%[0-9]+]]:fpr128 = IMPLICIT_DEF
-    ; CHECK: [[INSERT_SUBREG1:%[0-9]+]]:fpr128 = INSERT_SUBREG [[DEF1]], [[COPY1]], %subreg.dsub
-    ; CHECK: [[INSvi64lane:%[0-9]+]]:fpr128 = INSvi64lane [[INSERT_SUBREG]], 1, [[INSERT_SUBREG1]], 0
+    ; CHECK: [[INSERT_SUBREG1:%[0-9]+]]:fpr128 = INSERT_SUBREG [[DEF1]], [[COPY]], %subreg.dsub
+    ; CHECK: [[INSvi64lane:%[0-9]+]]:fpr128 = INSvi64lane [[INSERT_SUBREG1]], 1, [[INSERT_SUBREG]], 0
     ; CHECK: $q0 = COPY [[INSvi64lane]]
-    ; CHECK: RET_ReallyLR
+    ; CHECK: RET_ReallyLR implicit $q0
     %0:fpr(<4 x s16>) = COPY $d0
     %1:fpr(<4 x s16>) = COPY $d1
     %2:fpr(<8 x s16>) = G_CONCAT_VECTORS %0(<4 x s16>), %1(<4 x s16>)
     $q0 = COPY %2(<8 x s16>)
-    RET_ReallyLR
+    RET_ReallyLR implicit $q0
 
 ...

llvm/test/CodeGen/AArch64/GlobalISel/select-int-ext.mir

registers:
   - { id: 0, class: gpr }
   - { id: 1, class: gpr }
 
 body:             |
   bb.0:
     liveins: $w0
 
     ; CHECK-LABEL: name: anyext_s64_from_s32
-    ; CHECK: [[COPY:%[0-9]+]]:gpr32all = COPY $w0
-    ; CHECK: [[SUBREG_TO_REG:%[0-9]+]]:gpr64all = SUBREG_TO_REG 0, [[COPY]], %subreg.sub_32
-    ; CHECK: $x0 = COPY [[SUBREG_TO_REG]]
+    ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $w0
+    ; CHECK: [[DEF:%[0-9]+]]:gpr64all = IMPLICIT_DEF
+    ; CHECK: [[INSERT_SUBREG:%[0-9]+]]:gpr64all = INSERT_SUBREG [[DEF]], [[COPY]], %subreg.sub_32
+    ; CHECK: $x0 = COPY [[INSERT_SUBREG]]
     %0(s32) = COPY $w0
     %1(s64) = G_ANYEXT %0
     $x0 = COPY %1(s64)
 ...
 
 ---
 name:            anyext_s32_from_s8
 legalized:       true
 regBankSelected: true
 
 registers:
   - { id: 0, class: gpr }
   - { id: 1, class: gpr }
 
 body:             |
   bb.0:
     liveins: $w0
 
     ; CHECK-LABEL: name: anyext_s32_from_s8
     ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $w0
-    ; CHECK: [[COPY2:%[0-9]+]]:gpr32all = COPY [[COPY]]
-    ; CHECK: $w0 = COPY [[COPY2]]
+    ; CHECK: [[COPY1:%[0-9]+]]:gpr32all = COPY [[COPY]]
+    ; CHECK: $w0 = COPY [[COPY1]]
     %2:gpr(s32) = COPY $w0
     %0(s8) = G_TRUNC %2
     %1(s32) = G_ANYEXT %0
     $w0 = COPY %1(s32)
 ...
 
 ---
 name:            anyext_v8s16_from_v8s8

 
 body:             |
   bb.0:
     liveins: $w0
 
     ; CHECK-LABEL: name: zext_s16_from_s8
     ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $w0
     ; CHECK: [[UBFMWri:%[0-9]+]]:gpr32 = UBFMWri [[COPY]], 0, 7
-    ; CHECK: [[COPY2:%[0-9]+]]:gpr32all = COPY [[UBFMWri]]
-    ; CHECK: $w0 = COPY [[COPY2]]
+    ; CHECK: [[COPY1:%[0-9]+]]:gpr32all = COPY [[UBFMWri]]
+    ; CHECK: $w0 = COPY [[COPY1]]
     %2:gpr(s32) = COPY $w0
     %0(s8) = G_TRUNC %2
     %1(s16) = G_ZEXT %0
     %3:gpr(s32) = G_ANYEXT %1
     $w0 = COPY %3(s32)
 ...
 
 ---
registers:
   - { id: 1, class: gpr }
 
 body:             |
   bb.0:
     liveins: $w0
 
     ; CHECK-LABEL: name: sext_s64_from_s32
     ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $w0
-    ; CHECK: [[SUBREG_TO_REG:%[0-9]+]]:gpr64 = SUBREG_TO_REG 0, [[COPY]], %subreg.sub_32
-    ; CHECK: [[SBFMXri:%[0-9]+]]:gpr64 = SBFMXri [[SUBREG_TO_REG]], 0, 31
+    ; CHECK: [[DEF:%[0-9]+]]:gpr64all = IMPLICIT_DEF
+    ; CHECK: [[INSERT_SUBREG:%[0-9]+]]:gpr64 = INSERT_SUBREG [[DEF]], [[COPY]], %subreg.sub_32
+    ; CHECK: [[SBFMXri:%[0-9]+]]:gpr64 = SBFMXri [[INSERT_SUBREG]], 0, 31
     ; CHECK: $x0 = COPY [[SBFMXri]]
     %0(s32) = COPY $w0
     %1(s64) = G_SEXT %0
     $x0 = COPY %1(s64)
 ...
 
 ---
 name:            sext_s32_from_s16

 
 body:             |
   bb.0:
     liveins: $w0
 
     ; CHECK-LABEL: name: sext_s16_from_s8
     ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $w0
     ; CHECK: [[SBFMWri:%[0-9]+]]:gpr32 = SBFMWri [[COPY]], 0, 7
-    ; CHECK: [[COPY2:%[0-9]+]]:gpr32all = COPY [[SBFMWri]]
-    ; CHECK: $w0 = COPY [[COPY2]]
+    ; CHECK: [[COPY1:%[0-9]+]]:gpr32all = COPY [[SBFMWri]]
+    ; CHECK: $w0 = COPY [[COPY1]]
     %2:gpr(s32) = COPY $w0
     %0(s8) = G_TRUNC %2
     %1(s16) = G_SEXT %0
     %3:gpr(s32) = G_ANYEXT %1
     $w0 = COPY %3(s32)
 ...
 
 ---

llvm/test/CodeGen/X86/GlobalISel/select-copy.mir

 name:            test_copy6
 # ALL-LABEL: name:  test_copy6
 alignment:       4
 legalized:       true
 regBankSelected: true
 # ALL:      registers:
 # ALL-NEXT:   - { id: 0, class: gr32, preferred-register: '' }
 # ALL-NEXT:   - { id: 1, class: gr16, preferred-register: '' }
-# ALL-NEXT:   - { id: 2, class: gr32, preferred-register: '' }
+# ALL-NEXT:   - { id: 2, class: low32_addr_access_rbp, preferred-register: '' }
+# ALL-NEXT:   - { id: 3, class: low32_addr_access_rbp, preferred-register: '' }
 registers:
   - { id: 0, class: gpr, preferred-register: '' }
   - { id: 1, class: gpr, preferred-register: '' }
   - { id: 2, class: gpr, preferred-register: '' }
-# ALL           %0:gr32 = COPY $edx
-# ALL-NEXT      %1:gr16 = COPY %0.sub_16bit
-# ALL-NEXT      %2:gr32 = SUBREG_TO_REG 0, %1, %subreg.sub_16bit
-# ALL-NEXT      $eax = COPY %2
-# ALL-NEXT      RET 0, implicit $eax
+# ALL:         %0:gr32 = COPY $edx
+# ALL-NEXT:    %1:gr16 = COPY %0.sub_16bit
+# ALL-NEXT:    %3:low32_addr_access_rbp = IMPLICIT_DEF
+# ALL-NEXT:    %2:low32_addr_access_rbp = INSERT_SUBREG %3, %1, %subreg.sub_16bit
+# ALL-NEXT:    $eax = COPY %2
+# ALL-NEXT:    RET 0, implicit $eax
 body:             |
   bb.1 (%ir-block.0):
     liveins: $eax,$edx
 
     %0(s32) = COPY $edx
     %1(s16) = G_TRUNC %0(s32)
     %2(s32) = G_ANYEXT %1(s16)
     $eax = COPY %2(s32)
     RET 0, implicit $eax
 
 ...
-

llvm/test/CodeGen/X86/GlobalISel/select-ext-x86-64.mir

registers:
   - { id: 2, class: gpr }
 body:             |
   bb.1 (%ir-block.0):
     liveins: $edi
 
     ; ALL-LABEL: name: anyext_s64_from_s32
     ; ALL: [[COPY:%[0-9]+]]:gr64 = COPY $rdi
     ; ALL: [[COPY1:%[0-9]+]]:gr32 = COPY [[COPY]].sub_32bit
-    ; ALL: [[SUBREG_TO_REG:%[0-9]+]]:gr64 = SUBREG_TO_REG 0, [[COPY1]], %subreg.sub_32bit
-    ; ALL: $rax = COPY [[SUBREG_TO_REG]]
+    ; ALL: [[DEF:%[0-9]+]]:gr64 = IMPLICIT_DEF
+    ; ALL: [[INSERT_SUBREG:%[0-9]+]]:gr64 = INSERT_SUBREG [[DEF]], [[COPY1]], %subreg.sub_32bit
+    ; ALL: $rax = COPY [[INSERT_SUBREG]]
     ; ALL: RET 0, implicit $rax
     %0(s64) = COPY $rdi
     %1(s32) = G_TRUNC %0(s64)
     %2(s64) = G_ANYEXT %1(s32)
     $rax = COPY %2(s64)
     RET 0, implicit $rax
 ...

llvm/test/CodeGen/X86/GlobalISel/select-ext.mir

 name:            test_anyext_i16toi32
 # ALL-LABEL: name:  test_anyext_i16toi32
 alignment:       4
 legalized:       true
 regBankSelected: true
 # ALL:      registers:
 # ALL-NEXT:   - { id: 0, class: gr32, preferred-register: '' }
 # ALL-NEXT:   - { id: 1, class: gr16, preferred-register: '' }
-# ALL-NEXT:   - { id: 2, class: gr32, preferred-register: '' }
+# ALL-NEXT:   - { id: 2, class: low32_addr_access_rbp, preferred-register: '' }
+# ALL-NEXT:   - { id: 3, class: low32_addr_access_rbp, preferred-register: '' }
 registers:
   - { id: 0, class: gpr }
   - { id: 1, class: gpr }
   - { id: 2, class: gpr }
 # ALL:          %0:gr32 = COPY $edi
 # ALL-NEXT:     %1:gr16 = COPY %0.sub_16bit
-# ALL-NEXT:     %2:gr32 = SUBREG_TO_REG 0, %1, %subreg.sub_16bit
+# ALL-NEXT:     %3:low32_addr_access_rbp = IMPLICIT_DEF
+# ALL-NEXT:     %2:low32_addr_access_rbp = INSERT_SUBREG %3, %1, %subreg.sub_16bit
 # ALL-NEXT:     $eax = COPY %2
 # ALL-NEXT:     RET 0, implicit $eax
 body:             |
   bb.1 (%ir-block.0):
     liveins: $edi
 
     %0(s32) = COPY $edi
     %1(s16) = G_TRUNC %0(s32)
     %2(s32) = G_ANYEXT %1(s16)
     $eax = COPY %2(s32)
     RET 0, implicit $eax
 ...

llvm/test/CodeGen/X86/GlobalISel/x86_64-select-zext.mir

registers:
   - { id: 4, class: gpr }
 body:             |
   bb.1 (%ir-block.0):
     liveins: $edi
 
     ; CHECK-LABEL: name: zext_i1_to_i64
     ; CHECK: liveins: $edi
     ; CHECK: [[COPY:%[0-9]+]]:gr32 = COPY $edi
-    ; CHECK: [[SUBREG_TO_REG:%[0-9]+]]:gr64 = SUBREG_TO_REG 0, [[COPY]], %subreg.sub_32bit
-    ; CHECK: [[AND64ri8_:%[0-9]+]]:gr64 = AND64ri8 [[SUBREG_TO_REG]], 1, implicit-def $eflags
+    ; CHECK: [[DEF:%[0-9]+]]:gr64 = IMPLICIT_DEF
+    ; CHECK: [[INSERT_SUBREG:%[0-9]+]]:gr64 = INSERT_SUBREG [[DEF]], [[COPY]], %subreg.sub_32bit
+    ; CHECK: [[AND64ri8_:%[0-9]+]]:gr64 = AND64ri8 [[INSERT_SUBREG]], 1, implicit-def $eflags
     ; CHECK: $rax = COPY [[AND64ri8_]]
     ; CHECK: RET 0, implicit $rax
     %1:gpr(s32) = COPY $edi
     %3:gpr(s64) = G_CONSTANT i64 1
     %4:gpr(s64) = G_ANYEXT %1(s32)
     %2:gpr(s64) = G_AND %4, %3
     $rax = COPY %2(s64)
     RET 0, implicit $rax
registers:
   - { id: 4, class: gpr }
 body:             |
   bb.1 (%ir-block.0):
     liveins: $edi
 
     ; CHECK-LABEL: name: zext_i8_to_i64
     ; CHECK: liveins: $edi
     ; CHECK: [[COPY:%[0-9]+]]:gr32 = COPY $edi
-    ; CHECK: [[SUBREG_TO_REG:%[0-9]+]]:gr64 = SUBREG_TO_REG 0, [[COPY]], %subreg.sub_32bit
-    ; CHECK: [[AND64ri32_:%[0-9]+]]:gr64 = AND64ri32 [[SUBREG_TO_REG]], 255, implicit-def $eflags
+    ; CHECK: [[DEF:%[0-9]+]]:gr64 = IMPLICIT_DEF
+    ; CHECK: [[INSERT_SUBREG:%[0-9]+]]:gr64 = INSERT_SUBREG [[DEF]], [[COPY]], %subreg.sub_32bit
+    ; CHECK: [[AND64ri32_:%[0-9]+]]:gr64 = AND64ri32 [[INSERT_SUBREG]], 255, implicit-def $eflags
     ; CHECK: $rax = COPY [[AND64ri32_]]
     ; CHECK: RET 0, implicit $rax
     %1:gpr(s32) = COPY $edi
     %3:gpr(s64) = G_CONSTANT i64 255
     %4:gpr(s64) = G_ANYEXT %1(s32)
     %2:gpr(s64) = G_AND %4, %3
     $rax = COPY %2(s64)
     RET 0, implicit $rax
registers:
   - { id: 4, class: gpr }
 body:             |
   bb.1 (%ir-block.0):
     liveins: $edi
 
     ; CHECK-LABEL: name: zext_i16_to_i64
     ; CHECK: liveins: $edi
     ; CHECK: [[COPY:%[0-9]+]]:gr32 = COPY $edi
-    ; CHECK: [[SUBREG_TO_REG:%[0-9]+]]:gr64 = SUBREG_TO_REG 0, [[COPY]], %subreg.sub_32bit
-    ; CHECK: [[AND64ri32_:%[0-9]+]]:gr64 = AND64ri32 [[SUBREG_TO_REG]], 65535, implicit-def $eflags
+    ; CHECK: [[DEF:%[0-9]+]]:gr64 = IMPLICIT_DEF
+    ; CHECK: [[INSERT_SUBREG:%[0-9]+]]:gr64 = INSERT_SUBREG [[DEF]], [[COPY]], %subreg.sub_32bit
+    ; CHECK: [[AND64ri32_:%[0-9]+]]:gr64 = AND64ri32 [[INSERT_SUBREG]], 65535, implicit-def $eflags
     ; CHECK: $rax = COPY [[AND64ri32_]]
     ; CHECK: RET 0, implicit $rax
     %1:gpr(s32) = COPY $edi
     %3:gpr(s64) = G_CONSTANT i64 65535
     %4:gpr(s64) = G_ANYEXT %1(s32)
     %2:gpr(s64) = G_AND %4, %3
     $rax = COPY %2(s64)
     RET 0, implicit $rax

llvm/test/TableGen/GlobalISelEmitterInsertSubreg.td

+// RUN: llvm-tblgen %s -gen-global-isel -warn-on-skipped-patterns -I %p/../../include -I %p/Common -o - 2> %t.skipped | FileCheck %s --enable-var-scope
+// RUN: cat %t.skipped | FileCheck %s --check-prefix=SKIPPED
+
+include "llvm/Target/Target.td"
+include "GlobalISelEmitterCommon.td"
+
+// Boilerplate code for setting up some registers with subregs.
+class MyReg<string n, list<Register> subregs = []>
+  : Register<n> {
+  let SubRegs = subregs;
+}
+
+class MyClass<int size, list<ValueType> types, dag registers>
+  : RegisterClass<"Test", types, size, registers> {
+  let Size = size;
+}
+
+def sub0 : SubRegIndex<16>;
+def sub1 : SubRegIndex<16, 16>;
+def S0 : MyReg<"s0">;
+def S1 : MyReg<"s1">;
+def S2 : MyReg<"s14">;
+def S3 : MyReg<"s15">;
+def SRegs : MyClass<16, [i16], (sequence "S%u", 0, 3)>;
+
+let SubRegIndices = [sub0, sub1] in {
+def D0 : MyReg<"d0", [S0, S1]>;
+def E0 : MyReg<"e0", [S2, S3]>;
+}
+
+def DRegs : MyClass<32, [i32], (sequence "D%u", 0, 0)>;
+def ERegs : MyClass<32, [i32], (sequence "E%u", 0, 0)>;
+def SOP : RegisterOperand<SRegs>;
+def DOP : RegisterOperand<DRegs>;
+def SOME_INSN : I<(outs DRegs:$dst), (ins DOP:$src), []>;
+
+// We should skip cases where we don't have a given register class for the
+// subregister source.
+// SKIPPED: def : Pat<(i32 (anyext i16:$src)), (INSERT_SUBREG (i32 (IMPLICIT_DEF)), i16:$src, sub0)>;
+// SKIPPED: def : Pat<(i32 (anyext i16:$src)), (SOME_INSN (INSERT_SUBREG (i32 (IMPLICIT_DEF)), i16:$src, sub0))>;
+def : Pat<(i32 (anyext i16:$src)), (INSERT_SUBREG (i32 (IMPLICIT_DEF)), i16:$src, sub0)>;
+def : Pat<(i32 (anyext i16:$src)), (SOME_INSN (INSERT_SUBREG (i32 (IMPLICIT_DEF)), i16:$src, sub0))>;
+
+// Test that we import INSERT_SUBREG when its subregister source has a given
+// class.
+def : Pat<(i32 (anyext i16:$src)), (INSERT_SUBREG (i32 (IMPLICIT_DEF)), SOP:$src, sub0)>;
+// CHECK-LABEL:  (anyext:{ *:[i32] } i16:{ *:[i16] }:$src)  =>  (INSERT_SUBREG:{ *:[i32] } (IMPLICIT_DEF:{ *:[i32] }), SOP:{ *:[i16] }:$src, sub0:{ *:[i32] })
+// CHECK-NEXT:            GIR_MakeTempReg, /*TempRegID*/0, /*TypeID*/GILLT_s32,
+// CHECK-NEXT:            GIR_BuildMI, /*InsnID*/1, /*Opcode*/TargetOpcode::IMPLICIT_DEF,
+// CHECK-NEXT:            GIR_AddTempRegister, /*InsnID*/1, /*TempRegID*/0, /*TempRegFlags*/RegState::Define,
+// CHECK-NEXT:            GIR_ConstrainSelectedInstOperands, /*InsnID*/1,
+// CHECK-NEXT:            GIR_BuildMI, /*InsnID*/0, /*Opcode*/TargetOpcode::INSERT_SUBREG,
+// CHECK-NEXT:            GIR_Copy, /*NewInsnID*/0, /*OldInsnID*/0, /*OpIdx*/0, // dst
+// CHECK-NEXT:            GIR_AddTempRegister, /*InsnID*/0, /*TempRegID*/0, /*TempRegFlags*/0,
+// CHECK-NEXT:            GIR_Copy, /*NewInsnID*/0, /*OldInsnID*/0, /*OpIdx*/1, // src
+// CHECK-NEXT:            GIR_AddImm, /*InsnID*/0, /*Imm*/1,
+// CHECK-NEXT:            GIR_EraseFromParent, /*InsnID*/0,
+// CHECK-NEXT:            GIR_ConstrainOperandRC, /*InsnID*/0, /*Op*/0, /*RC DRegs*/1,
+// CHECK-NEXT:            GIR_ConstrainOperandRC, /*InsnID*/0, /*Op*/1, /*RC DRegs*/1,
+// CHECK-NEXT:            GIR_ConstrainOperandRC, /*InsnID*/0, /*Op*/2, /*RC SRegs*/0,
+
+
+// Test that we can import INSERT_SUBREG when it is a subinstruction of another
+// instruction.
+def : Pat<(i32 (anyext i16:$src)), (SOME_INSN (INSERT_SUBREG (i32 (IMPLICIT_DEF)), SOP:$src, sub0))>;
+// CHECK-LABEL:  (anyext:{ *:[i32] } i16:{ *:[i16] }:$src)  =>  (SOME_INSN:{ *:[i32] } (INSERT_SUBREG:{ *:[i32] } (IMPLICIT_DEF:{ *:[i32] }), SOP:{ *:[i16] }:$src, sub0:{ *:[i32] }))
+// CHECK-NEXT:            GIR_MakeTempReg, /*TempRegID*/0, /*TypeID*/GILLT_s32,
+// CHECK-NEXT:            GIR_MakeTempReg, /*TempRegID*/1, /*TypeID*/GILLT_s32,
+// CHECK-NEXT:            GIR_BuildMI, /*InsnID*/2, /*Opcode*/TargetOpcode::IMPLICIT_DEF,
+// CHECK-NEXT:            GIR_AddTempRegister, /*InsnID*/2, /*TempRegID*/1, /*TempRegFlags*/RegState::Define,
+// CHECK-NEXT:            GIR_ConstrainSelectedInstOperands, /*InsnID*/2,
+// CHECK-NEXT:            GIR_BuildMI, /*InsnID*/1, /*Opcode*/TargetOpcode::INSERT_SUBREG,
+// CHECK-NEXT:            GIR_AddTempRegister, /*InsnID*/1, /*TempRegID*/0, /*TempRegFlags*/RegState::Define,
+// CHECK-NEXT:            GIR_AddTempRegister, /*InsnID*/1, /*TempRegID*/1, /*TempRegFlags*/0,
+// CHECK-NEXT:            GIR_Copy, /*NewInsnID*/1, /*OldInsnID*/0, /*OpIdx*/1, // src
+// CHECK-NEXT:            GIR_AddImm, /*InsnID*/1, /*Imm*/1,
+// CHECK-NEXT:            GIR_ConstrainOperandRC, /*InsnID*/1, /*Op*/0, /*RC DRegs*/1,
+// CHECK-NEXT:            GIR_ConstrainOperandRC, /*InsnID*/1, /*Op*/1, /*RC DRegs*/1,
+// CHECK-NEXT:            GIR_ConstrainOperandRC, /*InsnID*/1, /*Op*/2, /*RC SRegs*/0,
+// CHECK-NEXT:            GIR_BuildMI, /*InsnID*/0, /*Opcode*/MyTarget::SOME_INSN,
+// 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,
+
+
+// Test that we correctly infer the super register class for INSERT_SUBREG when
+// we have COPY_TO_REGCLASS. We want to make sure we get an E register here,
+// not a D register.
+def : Pat<(i32 (anyext i16:$src)), (INSERT_SUBREG (i32 (COPY_TO_REGCLASS SOP:$src, ERegs)), SOP:$src, sub0)>;
+// CHECK-LABEL:  (anyext:{ *:[i32] } i16:{ *:[i16] }:$src)  =>  (INSERT_SUBREG:{ *:[i32] } (COPY_TO_REGCLASS:{ *:[i32] } SOP:{ *:[i16] }:$src, ERegs:{ *:[i32] }), SOP:{ *:[i16] }:$src, sub0:{ *:[i32] })
+// CHECK:                GIR_BuildMI, /*InsnID*/0, /*Opcode*/TargetOpcode::INSERT_SUBREG,
+// CHECK-DAG:            GIR_ConstrainOperandRC, /*InsnID*/0, /*Op*/0, /*RC ERegs*/2,
+// CHECK-NEXT:           GIR_ConstrainOperandRC, /*InsnID*/0, /*Op*/1, /*RC ERegs*/2,
+// CHECK-NEXT:           GIR_ConstrainOperandRC, /*InsnID*/0, /*Op*/2, /*RC SRegs*/0,
+
+// Test that we can import INSERT_SUBREG when its subregister source is defined
+// by a subinstruction.
+def SUBSOME_INSN : I<(outs SRegs:$dst), (ins SOP:$src), []>;
+def : Pat<(i32 (anyext i16:$src)), (INSERT_SUBREG (i32 (IMPLICIT_DEF)), (SUBSOME_INSN SOP:$src), sub0)>;
+// CHECK-LABEL:  (anyext:{ *:[i32] } i16:{ *:[i16] }:$src)  =>  (INSERT_SUBREG:{ *:[i32] } (IMPLICIT_DEF:{ *:[i32] }), (SUBSOME_INSN:{ *:[i16] } SOP:{ *:[i16] }:$src), sub0:{ *:[i32] })
+// CHECK-NEXT:          GIR_MakeTempReg, /*TempRegID*/0, /*TypeID*/GILLT_s32,
+// CHECK-NEXT:          GIR_MakeTempReg, /*TempRegID*/1, /*TypeID*/GILLT_s16,
+// CHECK-NEXT:          GIR_BuildMI, /*InsnID*/2, /*Opcode*/MyTarget::SUBSOME_INSN,
+// CHECK-NEXT:          GIR_AddTempRegister, /*InsnID*/2, /*TempRegID*/1, /*TempRegFlags*/RegState::Define,
+// CHECK-NEXT:          GIR_Copy, /*NewInsnID*/2, /*OldInsnID*/0, /*OpIdx*/1, // src
+// CHECK-NEXT:          GIR_ConstrainSelectedInstOperands, /*InsnID*/2,
+// CHECK-NEXT:          GIR_BuildMI, /*InsnID*/1, /*Opcode*/TargetOpcode::IMPLICIT_DEF,
+// CHECK-NEXT:          GIR_AddTempRegister, /*InsnID*/1, /*TempRegID*/0, /*TempRegFlags*/RegState::Define,
+// CHECK-NEXT:          GIR_ConstrainSelectedInstOperands, /*InsnID*/1,
+// CHECK-NEXT:          GIR_BuildMI, /*InsnID*/0, /*Opcode*/TargetOpcode::INSERT_SUBREG,
+// CHECK-NEXT:          GIR_Copy, /*NewInsnID*/0, /*OldInsnID*/0, /*OpIdx*/0, // dst
+// CHECK-NEXT:          GIR_AddTempRegister, /*InsnID*/0, /*TempRegID*/0, /*TempRegFlags*/0,
+// CHECK-NEXT:          GIR_AddTempRegister, /*InsnID*/0, /*TempRegID*/1, /*TempRegFlags*/0,
+// CHECK-NEXT:          GIR_AddImm, /*InsnID*/0, /*Imm*/1,
+// CHECK-NEXT:          GIR_EraseFromParent, /*InsnID*/0,
+// CHECK-NEXT:          GIR_ConstrainOperandRC, /*InsnID*/0, /*Op*/0, /*RC DRegs*/1,
+// CHECK-NEXT:          GIR_ConstrainOperandRC, /*InsnID*/0, /*Op*/1, /*RC DRegs*/1,
+// CHECK-NEXT:          GIR_ConstrainOperandRC, /*InsnID*/0, /*Op*/2, /*RC SRegs*/0,

llvm/utils/TableGen/CodeGenTarget.h

public:
 
   /// getAsmWriter - Return the AssemblyWriter definition for this target.
   ///
   Record *getAsmWriter() const;
 
   /// getRegBank - Return the register bank description.
   CodeGenRegBank &getRegBank() const;
 
+  /// Return the largest register class on \p RegBank which supports \p Ty and
+  /// covers \p SubIdx if it exists.
+  Optional<CodeGenRegisterClass *>
+  getSuperRegForSubReg(const ValueTypeByHwMode &Ty, CodeGenRegBank &RegBank,
+                       const CodeGenSubRegIndex *SubIdx) const;
+
   /// getRegisterByName - If there is a register with the specific AsmName,
   /// return it.
   const CodeGenRegister *getRegisterByName(StringRef Name) const;
 
   const std::vector<Record*> &getRegAltNameIndices() const {
     if (RegAltNameIndices.empty()) ReadRegAltNameIndices();
     return RegAltNameIndices;
   }

llvm/utils/TableGen/CodeGenTarget.cpp

 }
 
 CodeGenRegBank &CodeGenTarget::getRegBank() const {
   if (!RegBank)
     RegBank = std::make_unique<CodeGenRegBank>(Records, getHwModes());
   return *RegBank;
 }
 
+Optional<CodeGenRegisterClass *>
+CodeGenTarget::getSuperRegForSubReg(const ValueTypeByHwMode &ValueTy,
+                                    CodeGenRegBank &RegBank,
+                                    const CodeGenSubRegIndex *SubIdx) const {
+  std::vector<CodeGenRegisterClass *> Candidates;
+  auto &RegClasses = RegBank.getRegClasses();
+
+  // Try to find a register class which supports ValueTy, and also contains
+  // SubIdx.
+  for (CodeGenRegisterClass &RC : RegClasses) {
+    // Is there a subclass of this class which contains this subregister index?
+    CodeGenRegisterClass *SubClassWithSubReg = RC.getSubClassWithSubReg(SubIdx);
+    if (!SubClassWithSubReg)
+      continue;
+
+    // We have a class. Check if it supports this value type.
+    if (llvm::none_of(SubClassWithSubReg->VTs,
+                      [&ValueTy](const ValueTypeByHwMode &ClassVT) {
+                        return ClassVT == ValueTy;
+                      }))
+      continue;
+
+    // We have a register class which supports both the value type and
+    // subregister index. Remember it.
+    Candidates.push_back(SubClassWithSubReg);
+  }
+
+  // If we didn't find anything, we're done.
+  if (Candidates.empty())
+    return None;
+
+  // Find and return the largest of our candidate classes.
+  llvm::sort(Candidates,
+             [&](const CodeGenRegisterClass *A, const CodeGenRegisterClass *B) {
+               return A->getMembers().size() > B->getMembers().size();
+             });
+
+  return Candidates[0];
+}
+
 void CodeGenTarget::ReadRegAltNameIndices() const {
   RegAltNameIndices = Records.getAllDerivedDefinitions("RegAltNameIndex");
   llvm::sort(RegAltNameIndices, LessRecord());
 }
 
 /// getRegisterByName - If there is a register with the specific AsmName,
 /// return it.
 const CodeGenRegister *CodeGenTarget::getRegisterByName(StringRef Name) const {

llvm/utils/TableGen/GlobalISelEmitter.cpp

private:
   /// Otherwise, return an Error explaining why we don't support it.
   Expected<RuleMatcher> runOnPattern(const PatternToMatch &P);
 
   void declareSubtargetFeature(Record *Predicate);
 
   MatchTable buildMatchTable(MutableArrayRef<RuleMatcher> Rules, bool Optimize,
                              bool WithCoverage);
 
+  /// Infer a CodeGenRegisterClass for the type of \p SuperRegNode. The returned
+  /// CodeGenRegisterClass will support the CodeGenRegisterClass of
+  /// \p SubRegNode, and the subregister index defined by \p SubRegIdxNode.
+  /// If no register class is found, return None.
+  Optional<const CodeGenRegisterClass *>
+  inferSuperRegisterClass(const TypeSetByHwMode &Ty,
+                          TreePatternNode *SuperRegNode,
+                          TreePatternNode *SubRegIdxNode);
+
+  /// Return the CodeGenRegisterClass associated with \p Leaf if it has one.
+  Optional<const CodeGenRegisterClass *>
+  getRegClassFromLeaf(TreePatternNode *Leaf);
+
+  /// Return a CodeGenRegisterClass for \p N if one can be found. Return None
+  /// otherwise.
+  Optional<const CodeGenRegisterClass *>
+  inferRegClassFromPattern(TreePatternNode *N);
+
 public:
   /// Takes a sequence of \p Rules and group them based on the predicates
   /// they share. \p MatcherStorage is used as a memory container
   /// for the group that are created as part of this process.
   ///
   /// What this optimization does looks like if GroupT = GroupMatcher:
   /// Output without optimization:
   /// \verbatim
if (ChildRec->isSubClassOf("RegisterClass") ||
             DstChild->getName(), ChildRec->getValueAsDef("GIZeroRegister"));
         return InsertPt;
       }
 
       DstMIBuilder.addRenderer<CopyRenderer>(DstChild->getName());
       return InsertPt;
     }
 
+    if (ChildRec->isSubClassOf("SubRegIndex")) {
+      CodeGenSubRegIndex *SubIdx = CGRegs.getSubRegIdx(ChildRec);
+      DstMIBuilder.addRenderer<ImmRenderer>(SubIdx->EnumValue);
+      return InsertPt;
+    }
+
     if (ChildRec->isSubClassOf("ComplexPattern")) {
       const auto &ComplexPattern = ComplexPatternEquivs.find(ChildRec);
       if (ComplexPattern == ComplexPatternEquivs.end())
         return failedImport(
             "SelectionDAG ComplexPattern not mapped to GlobalISel");
 
       const OperandMatcher &OM = Rule.getOperandMatcher(DstChild->getName());
       DstMIBuilder.addRenderer<RenderComplexPatternOperand>(
GlobalISelEmitter::createAndImportSubInstructionRenderer(
   // Assign the result to TempReg.
   DstMIBuilder.addRenderer<TempRegRenderer>(TempRegID, true);
 
   InsertPtOrError =
       importExplicitUseRenderers(InsertPtOrError.get(), M, DstMIBuilder, Dst);
   if (auto Error = InsertPtOrError.takeError())
     return std::move(Error);
 
+  // We need to make sure that when we import an INSERT_SUBREG as a
+  // subinstruction that it ends up being constrained to the correct super
+  // register and subregister classes.
+  if (Target.getInstruction(Dst->getOperator()).TheDef->getName() ==
+      "INSERT_SUBREG") {
+    auto SubClass = inferRegClassFromPattern(Dst->getChild(1));
+    if (!SubClass)
+      return failedImport(
+          "Cannot infer register class from INSERT_SUBREG operand #1");
+    Optional<const CodeGenRegisterClass *> SuperClass = inferSuperRegisterClass(
+        Dst->getExtType(0), Dst->getChild(0), Dst->getChild(2));
+    if (!SuperClass)
+      return failedImport(
+          "Cannot infer register class for INSERT_SUBREG operand #0");
+    // The destination and the super register source of an INSERT_SUBREG must
+    // be the same register class.
+    M.insertAction<ConstrainOperandToRegClassAction>(
+        InsertPt, DstMIBuilder.getInsnID(), 0, **SuperClass);
+    M.insertAction<ConstrainOperandToRegClassAction>(
+        InsertPt, DstMIBuilder.getInsnID(), 1, **SuperClass);
+    M.insertAction<ConstrainOperandToRegClassAction>(
+        InsertPt, DstMIBuilder.getInsnID(), 2, **SubClass);
+    return InsertPtOrError.get();
+  }
+
   M.insertAction<ConstrainOperandsToDefinitionAction>(InsertPt,
                                                       DstMIBuilder.getInsnID());
   return InsertPtOrError.get();
 }
 
 Expected<action_iterator> GlobalISelEmitter::createInstructionRenderer(
     action_iterator InsertPt, RuleMatcher &M, const TreePatternNode *Dst) {
   Record *DstOp = Dst->getOperator();

 Error GlobalISelEmitter::importImplicitDefRenderers(
     BuildMIAction &DstMIBuilder,
     const std::vector<Record *> &ImplicitDefs) const {
   if (!ImplicitDefs.empty())
     return failedImport("Pattern defines a physical register");
   return Error::success();
 }
 
+Optional<const CodeGenRegisterClass *>
+GlobalISelEmitter::getRegClassFromLeaf(TreePatternNode *Leaf) {
+  assert(Leaf && "Expected node?");
+  assert(Leaf->isLeaf() && "Expected leaf?");
+  Record *RCRec = getInitValueAsRegClass(Leaf->getLeafValue());
+  if (!RCRec)
+    return None;
+  CodeGenRegisterClass *RC = CGRegs.getRegClass(RCRec);
+  if (!RC)
+    return None;
+  return RC;
+}
+
+Optional<const CodeGenRegisterClass *>
+GlobalISelEmitter::inferRegClassFromPattern(TreePatternNode *N) {
+  if (!N)
+    return None;
+
+  if (N->isLeaf())
+    return getRegClassFromLeaf(N);
+
+  // We don't have a leaf node, so we have to try and infer something. Check
+  // that we have an instruction that we an infer something from.
+
+  // Only handle things that produce a single type.
+  if (N->getNumTypes() != 1)
+    return None;
+  Record *OpRec = N->getOperator();
+
+  // We only want instructions.
+  if (!OpRec->isSubClassOf("Instruction"))
+    return None;
+
+  // Don't want to try and infer things when there could potentially be more
+  // than one candidate register class.
+  auto &Inst = Target.getInstruction(OpRec);
+  if (Inst.Operands.NumDefs > 1)
+    return None;
+
+  // Handle any special-case instructions which we can safely infer register
+  // classes from.
+  StringRef InstName = Inst.TheDef->getName();
+  if (InstName == "COPY_TO_REGCLASS") {
+    // If we have a COPY_TO_REGCLASS, then we need to handle it specially. It
+    // has the desired register class as the first child.
+    TreePatternNode *RCChild = N->getChild(1);
+    if (!RCChild->isLeaf())
+      return None;
+    return getRegClassFromLeaf(RCChild);
+  }
+
+  // Handle destination record types that we can safely infer a register class
+  // from.
+  const auto &DstIOperand = Inst.Operands[0];
+  Record *DstIOpRec = DstIOperand.Rec;
+  if (DstIOpRec->isSubClassOf("RegisterOperand")) {
+    DstIOpRec = DstIOpRec->getValueAsDef("RegClass");
+    const CodeGenRegisterClass &RC = Target.getRegisterClass(DstIOpRec);
+    return &RC;
+  }
+
+  if (DstIOpRec->isSubClassOf("RegisterClass")) {
+    const CodeGenRegisterClass &RC = Target.getRegisterClass(DstIOpRec);
+    return &RC;
+  }
+
+  return None;
+}
+
+Optional<const CodeGenRegisterClass *>
+GlobalISelEmitter::inferSuperRegisterClass(const TypeSetByHwMode &Ty,
+                                           TreePatternNode *SuperRegNode,
+                                           TreePatternNode *SubRegIdxNode) {
+  // Check if we already have a defined register class for the super register
+  // node. If we do, then we should preserve that rather than inferring anything
+  // from the subregister index node. We can assume that whoever wrote the
+  // pattern in the first place made sure that the super register and
+  // subregister are compatible.
+  if (Optional<const CodeGenRegisterClass *> SuperRegisterClass =
+          inferRegClassFromPattern(SuperRegNode))
+    return SuperRegisterClass;
+
+  // We need a ValueTypeByHwMode for getSuperRegForSubReg.
+  if (!Ty.isValueTypeByHwMode(false))
+    return None;
+
+  // We don't know anything about the super register. Try to use the subregister
+  // index to infer an appropriate register class.
+  if (!SubRegIdxNode->isLeaf())
+    return None;
+  DefInit *SubRegInit = dyn_cast<DefInit>(SubRegIdxNode->getLeafValue());
+  if (!SubRegInit)
+    return None;
+  CodeGenSubRegIndex *SubIdx = CGRegs.getSubRegIdx(SubRegInit->getDef());
+
+  // Use the information we found above to find a minimal register class which
+  // supports the subregister and type we want.
+  auto RC =
+      Target.getSuperRegForSubReg(Ty.getValueTypeByHwMode(), CGRegs, SubIdx);
+  return *RC;
+}
+
 Expected<RuleMatcher> GlobalISelEmitter::runOnPattern(const PatternToMatch &P) {
   // Keep track of the matchers and actions to emit.
   int Score = P.getPatternComplexity(CGP);
   RuleMatcher M(P.getSrcRecord()->getLoc());
   RuleMatcherScores[M.getRuleID()] = Score;
   M.addAction<DebugCommentAction>(llvm::to_string(*P.getSrcPattern()) +
                                   "  =>  " +
                                   llvm::to_string(*P.getDstPattern()));
if (DstI.TheDef->getName() == "COPY_TO_REGCLASS") {
       if (!Dst->getChild(0)->isLeaf())
         return failedImport("EXTRACT_SUBREG operand #0 isn't a leaf");
 
       // 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");
+    } else if (DstI.TheDef->getName() == "INSERT_SUBREG") {
+      auto MaybeSuperClass =
+          inferSuperRegisterClass(VTy, Dst->getChild(0), Dst->getChild(2));
+      if (!MaybeSuperClass)
         return failedImport(
-            "EXTRACT_SUBREG operand #0 isn't a register class");
+            "Cannot infer register class for INSERT_SUBREG operand #0");
+      // Move to the next pattern here, because the register class we found
+      // doesn't necessarily have a record associated with it. So, we can't
+      // set DstIOpRec using this.
+      OperandMatcher &OM = InsnMatcher.getOperand(OpIdx);
+      OM.setSymbolicName(DstIOperand.Name);
+      M.defineOperand(OM.getSymbolicName(), OM);
+      OM.addPredicate<RegisterBankOperandMatcher>(**MaybeSuperClass);
+      ++OpIdx;
+      continue;
     } else if (DstIOpRec->isSubClassOf("RegisterOperand"))
       DstIOpRec = DstIOpRec->getValueAsDef("RegClass");
     else if (!DstIOpRec->isSubClassOf("RegisterClass"))
       return failedImport("Dst MI def isn't a register class" +
                           to_string(*Dst));
 
     OperandMatcher &OM = InsnMatcher.getOperand(OpIdx);
     OM.setSymbolicName(DstIOperand.Name);
if (DstI.TheDef->getName() == "EXTRACT_SUBREG") {
     M.addAction<ConstrainOperandToRegClassAction>(0, 1, *SrcRCDstRCPair->first);
 
     // We're done with this pattern!  It's eligible for GISel emission; return
     // it.
     ++NumPatternImported;
     return std::move(M);
   }
 
+  if (DstI.TheDef->getName() == "INSERT_SUBREG") {
+    assert(Src->getExtTypes().size() == 1 &&
+           "Expected Src of INSERT_SUBREG to have one result type");
+    // We need to constrain the destination, a super regsister source, and a
+    // subregister source.
+    auto SubClass = inferRegClassFromPattern(Dst->getChild(1));
+    if (!SubClass)
+      return failedImport(
+          "Cannot infer register class from INSERT_SUBREG operand #1");
+    auto SuperClass = inferSuperRegisterClass(
+        Src->getExtType(0), Dst->getChild(0), Dst->getChild(2));
+    if (!SuperClass)
+      return failedImport(
+          "Cannot infer register class for INSERT_SUBREG operand #0");
+    M.addAction<ConstrainOperandToRegClassAction>(0, 0, **SuperClass);
+    M.addAction<ConstrainOperandToRegClassAction>(0, 1, **SuperClass);
+    M.addAction<ConstrainOperandToRegClassAction>(0, 2, **SubClass);
+    ++NumPatternImported;
+    return std::move(M);
+  }
+
   M.addAction<ConstrainOperandsToDefinitionAction>(0);
 
   // We're done with this pattern!  It's eligible for GISel emission; return it.
   ++NumPatternImported;
   return std::move(M);
 }
 
 // Emit imm predicate table and an enum to reference them with.