[GISel: Add support for CSEing SrcOps which are immediates

[aditya_nandakumar]

Summary

This came up in attempting to CSE a target pseudo opcode.

[arsenm]

Couldn't you test this with a G_EXTRACT?

[aditya_nandakumar]

Add G_EXTRACT to CSEConfigFull, and add unit test.

llvm/lib/CodeGen/GlobalISel/CSEInfo.cpp

bool CSEConfigFull::shouldCSEOpc(unsigned Opc) {
   case TargetOpcode::G_FCONSTANT:
   case TargetOpcode::G_IMPLICIT_DEF:
   case TargetOpcode::G_ZEXT:
   case TargetOpcode::G_SEXT:
   case TargetOpcode::G_ANYEXT:
   case TargetOpcode::G_UNMERGE_VALUES:
   case TargetOpcode::G_TRUNC:
   case TargetOpcode::G_PTR_ADD:
+  case TargetOpcode::G_EXTRACT:
     return true;
   }
   return false;
 }
 
 bool CSEConfigConstantOnly::shouldCSEOpc(unsigned Opc) {
   return Opc == TargetOpcode::G_CONSTANT || Opc == TargetOpcode::G_IMPLICIT_DEF;
 }

llvm/lib/CodeGen/GlobalISel/CSEMIRBuilder.cpp

default:
     B.addNodeIDRegType(Op.getLLTTy(*getMRI()));
     break;
   }
 }
 
 void CSEMIRBuilder::profileSrcOp(const SrcOp &Op,
                                  GISelInstProfileBuilder &B) const {
   switch (Op.getSrcOpKind()) {
+  case SrcOp::SrcType::Ty_Imm:
+    B.addNodeIDImmediate(static_cast<int64_t>(Op.getImm()));
+    break;
   case SrcOp::SrcType::Ty_Predicate:
     B.addNodeIDImmediate(static_cast<int64_t>(Op.getPredicate()));
     break;
   default:
     B.addNodeIDRegType(Op.getReg());
     break;
   }
 }

llvm/unittests/CodeGen/GlobalISel/CSETest.cpp

TEST_F(AArch64GISelMITest, TestCSE) {
   RegularBuilder.setInsertPt(*EntryMBB, EntryMBB->begin());
   auto NonCSEFMul = RegularBuilder.buildInstr(TargetOpcode::G_AND)
                         .addDef(MRI->createGenericVirtualRegister(s32))
                         .addUse(Copies[0])
                         .addUse(Copies[1]);
   auto CSEFMul =
       CSEB.buildInstr(TargetOpcode::G_AND, {s32}, {Copies[0], Copies[1]});
   EXPECT_EQ(&*CSEFMul, &*NonCSEFMul);
+
+  auto ExtractMIB = CSEB.buildInstr(TargetOpcode::G_EXTRACT, {s16},
+                                    {Copies[0], static_cast<uint64_t>(0)});
+  auto ExtractMIB1 = CSEB.buildInstr(TargetOpcode::G_EXTRACT, {s16},
+                                     {Copies[0], static_cast<uint64_t>(0)});
+  auto ExtractMIB2 = CSEB.buildInstr(TargetOpcode::G_EXTRACT, {s16},
+                                     {Copies[0], static_cast<uint64_t>(1)});
+  EXPECT_EQ(&*ExtractMIB, &*ExtractMIB1);
+  EXPECT_NE(&*ExtractMIB, &*ExtractMIB2);
 }
 
 TEST_F(AArch64GISelMITest, TestCSEConstantConfig) {
   setUp();
   if (!TM)
     return;
 
   LLT s16{LLT::scalar(16)};