[GlobalIsel] Add llvm.invariant.start and llvm.invariant.end

[paquette]

Summary

Port over the implementation in SelectionDAGBuilder.cpp into the IRTranslator and update the arm64-irtranslator test.

These were causing fallbacks in CTMark/Bullet (-Rpass-missed=gisel-select), and this patch fixes that.

[dsanders]

LGTM

[paquette]

Thanks! Committed in r343885. (https://reviews.llvm.org/rL343885)

lib/CodeGen/GlobalISel/IRTranslator.cpp

case Intrinsic::ctlz: {
     return true;
   }
   case Intrinsic::ctpop: {
     MIRBuilder.buildInstr(TargetOpcode::G_CTPOP)
         .addDef(getOrCreateVReg(CI))
         .addUse(getOrCreateVReg(*CI.getArgOperand(0)));
     return true;
   }
+  case Intrinsic::invariant_start: {
+    LLT PtrTy = getLLTForType(*CI.getArgOperand(0)->getType(), *DL);
+    unsigned Undef = MRI->createGenericVirtualRegister(PtrTy);
+    MIRBuilder.buildUndef(Undef);
+    return true;
+  }
+  case Intrinsic::invariant_end:
+    return true;
   }
   return false;
 }
 
 bool IRTranslator::translateInlineAsm(const CallInst &CI,
                                       MachineIRBuilder &MIRBuilder) {
   const InlineAsm &IA = cast<InlineAsm>(*CI.getCalledValue());
   if (!IA.getConstraintString().empty())

test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll

 ; CHECK-LABEL: name: test_blockaddress
 ; CHECK: [[BADDR:%[0-9]+]]:_(p0) = G_BLOCK_ADDR blockaddress(@test_blockaddress, %ir-block.block)
 ; CHECK: G_STORE [[BADDR]](p0)
   store i8* blockaddress(@test_blockaddress, %block), i8** @addr
   indirectbr i8* blockaddress(@test_blockaddress, %block), [label %block]
 block:
   ret void
 }
+
+%t = type { i32 }
+declare {}* @llvm.invariant.start.p0i8(i64, i8* nocapture) readonly nounwind
+declare void @llvm.invariant.end.p0i8({}*, i64, i8* nocapture) nounwind
+define void @test_invariant_intrin() {
+; CHECK-LABEL: name: test_invariant_intrin
+; CHECK: %{{[0-9]+}}:_(s64) = G_IMPLICIT_DEF
+; CHECK-NEXT: RET_ReallyLR
+  %x = alloca %t
+  %y = bitcast %t* %x to i8*
+  %inv = call {}* @llvm.invariant.start.p0i8(i64 8, i8* %y)
+  call void @llvm.invariant.end.p0i8({}* %inv, i64 8, i8* %y)
+  ret void
+}