[RISCV][NFC] Add generateMCInstSeq in RISCVMatInt (llvm#84462)

This allows to avoid duplicating the code handling the instructions
outputted by `generateInstSeq` when emitting `MCInst`s.

Author: Zeavee

llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp

@@ -3081,34 +3081,11 @@ void RISCVAsmParser::emitToStreamer(MCStreamer &S, const MCInst &Inst) {
 
 void RISCVAsmParser::emitLoadImm(MCRegister DestReg, int64_t Value,
                                  MCStreamer &Out) {
-  RISCVMatInt::InstSeq Seq = RISCVMatInt::generateInstSeq(Value, getSTI());
-
-  MCRegister SrcReg = RISCV::X0;
-  for (const RISCVMatInt::Inst &Inst : Seq) {
-    switch (Inst.getOpndKind()) {
-    case RISCVMatInt::Imm:
-      emitToStreamer(Out,
-                     MCInstBuilder(Inst.getOpcode()).addReg(DestReg).addImm(Inst.getImm()));
-      break;
-    case RISCVMatInt::RegX0:
-      emitToStreamer(
-          Out, MCInstBuilder(Inst.getOpcode()).addReg(DestReg).addReg(SrcReg).addReg(
-                   RISCV::X0));
-      break;
-    case RISCVMatInt::RegReg:
-      emitToStreamer(
-          Out, MCInstBuilder(Inst.getOpcode()).addReg(DestReg).addReg(SrcReg).addReg(
-                   SrcReg));
-      break;
-    case RISCVMatInt::RegImm:
-      emitToStreamer(
-          Out, MCInstBuilder(Inst.getOpcode()).addReg(DestReg).addReg(SrcReg).addImm(
-                   Inst.getImm()));
-      break;
-    }
+  SmallVector<MCInst, 8> Seq;
+  RISCVMatInt::generateMCInstSeq(Value, getSTI(), DestReg, Seq);
 
-    // Only the first instruction has X0 as its source.
-    SrcReg = DestReg;
+  for (MCInst &Inst : Seq) {
+    emitToStreamer(Out, Inst);
   }
 }
 

llvm/lib/Target/RISCV/MCTargetDesc/RISCVMatInt.cpp

@@ -9,6 +9,7 @@
 #include "RISCVMatInt.h"
 #include "MCTargetDesc/RISCVMCTargetDesc.h"
 #include "llvm/ADT/APInt.h"
+#include "llvm/MC/MCInstBuilder.h"
 #include "llvm/Support/MathExtras.h"
 using namespace llvm;
 
@@ -436,6 +437,43 @@ InstSeq generateInstSeq(int64_t Val, const MCSubtargetInfo &STI) {
   return Res;
 }
 
+void generateMCInstSeq(int64_t Val, const MCSubtargetInfo &STI,
+                       MCRegister DestReg, SmallVectorImpl<MCInst> &Insts) {
+  RISCVMatInt::InstSeq Seq = RISCVMatInt::generateInstSeq(Val, STI);
+
+  MCRegister SrcReg = RISCV::X0;
+  for (RISCVMatInt::Inst &Inst : Seq) {
+    switch (Inst.getOpndKind()) {
+    case RISCVMatInt::Imm:
+      Insts.push_back(MCInstBuilder(Inst.getOpcode())
+                          .addReg(DestReg)
+                          .addImm(Inst.getImm()));
+      break;
+    case RISCVMatInt::RegX0:
+      Insts.push_back(MCInstBuilder(Inst.getOpcode())
+                          .addReg(DestReg)
+                          .addReg(SrcReg)
+                          .addReg(RISCV::X0));
+      break;
+    case RISCVMatInt::RegReg:
+      Insts.push_back(MCInstBuilder(Inst.getOpcode())
+                          .addReg(DestReg)
+                          .addReg(SrcReg)
+                          .addReg(SrcReg));
+      break;
+    case RISCVMatInt::RegImm:
+      Insts.push_back(MCInstBuilder(Inst.getOpcode())
+                          .addReg(DestReg)
+                          .addReg(SrcReg)
+                          .addImm(Inst.getImm()));
+      break;
+    }
+
+    // Only the first instruction has X0 as its source.
+    SrcReg = DestReg;
+  }
+}
+
 InstSeq generateTwoRegInstSeq(int64_t Val, const MCSubtargetInfo &STI,
                               unsigned &ShiftAmt, unsigned &AddOpc) {
   int64_t LoVal = SignExtend64<32>(Val);

llvm/lib/Target/RISCV/MCTargetDesc/RISCVMatInt.h

@@ -10,6 +10,7 @@
 #define LLVM_LIB_TARGET_RISCV_MCTARGETDESC_MATINT_H
 
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/MC/MCRegister.h"
 #include "llvm/MC/MCSubtargetInfo.h"
 #include <cstdint>
 
@@ -48,6 +49,10 @@ using InstSeq = SmallVector<Inst, 8>;
 // instruction selection.
 InstSeq generateInstSeq(int64_t Val, const MCSubtargetInfo &STI);
 
+// Helper to generate the generateInstSeq instruction sequence using MCInsts
+void generateMCInstSeq(int64_t Val, const MCSubtargetInfo &STI,
+                       MCRegister DestReg, SmallVectorImpl<MCInst> &Insts);
+
 // Helper to generate an instruction sequence that can materialize the given
 // immediate value into a register using an additional temporary register. This
 // handles cases where the constant can be generated by (ADD (SLLI X, C), X) or