[llvm] [RISCV][GISEL] legalize, regbankselect, and instruction-select for G_… (PR #73061)

[Craig Topper via llvm-commits]

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@@ -564,11 +571,52 @@ bool RISCVInstructionSelector::select(MachineInstr &MI) {
     return selectSelect(MI, MIB, MRI);
   case TargetOpcode::G_FCMP:
     return selectFPCompare(MI, MIB, MRI);
+  case TargetOpcode::G_MERGE_VALUES:
+    return selectMergeValues(MI, MIB, MRI);
+  case TargetOpcode::G_UNMERGE_VALUES:
+    return selectUnmergeValues(MI, MIB, MRI);
   default:
     return false;
   }
 }
 
+bool RISCVInstructionSelector::selectMergeValues(
+    MachineInstr &MI, MachineIRBuilder &MIB, MachineRegisterInfo &MRI) const {
+  assert(MI.getOpcode() == TargetOpcode::G_MERGE_VALUES);
+
+  // Build a F64 Pair from operands
+  if (MI.getNumOperands() != 3)
+    return false;
+  Register Dst = MI.getOperand(0).getReg();
+  Register Lo = MI.getOperand(1).getReg();
+  Register Hi = MI.getOperand(2).getReg();
+  if (!isRegInFprb(Dst, MRI) || !(isRegInGprb(Lo, MRI) && isRegInGprb(Hi, MRI)))
+    return false;
+  MachineInstr *Result =
+      MIB.buildInstr(RISCV::BuildPairF64Pseudo, {Dst}, {Lo, Hi});
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topperc wrote:

Can this be setDesc?

https://github.com/llvm/llvm-project/pull/73061