[llvm] [RISCV] Add an experimental pseudoinstruction to represent a rematerializable constant materialization sequence. (PR #69983)

[Philip Reames via llvm-commits]

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@@ -0,0 +1,155 @@
+//===-- RISCVPostRAExpandPseudoInsts.cpp - Expand pseudo instrs ----===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains a pass that expands the pseudo instruction pseudolisimm32
+// into target instructions. This pass should be run during the post-regalloc
+// passes, before post RA scheduling.
+//
+//===----------------------------------------------------------------------===//
+
+#include "MCTargetDesc/RISCVMatInt.h"
+#include "RISCV.h"
+#include "RISCVInstrInfo.h"
+#include "RISCVTargetMachine.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+
+using namespace llvm;
+
+#define RISCV_POST_RA_EXPAND_PSEUDO_NAME                                       \
+  "RISC-V post-regalloc pseudo instruction expansion pass"
+
+namespace {
+
+class RISCVPostRAExpandPseudo : public MachineFunctionPass {
+public:
+  const RISCVInstrInfo *TII;
+  static char ID;
+
+  RISCVPostRAExpandPseudo() : MachineFunctionPass(ID) {
+    initializeRISCVPostRAExpandPseudoPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  StringRef getPassName() const override {
+    return RISCV_POST_RA_EXPAND_PSEUDO_NAME;
+  }
+
+private:
+  bool expandMBB(MachineBasicBlock &MBB);
+  bool expandMI(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
+                MachineBasicBlock::iterator &NextMBBI);
+  bool expandMovImm(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI);
+};
+
+char RISCVPostRAExpandPseudo::ID = 0;
+
+bool RISCVPostRAExpandPseudo::runOnMachineFunction(MachineFunction &MF) {
+  TII = static_cast<const RISCVInstrInfo *>(MF.getSubtarget().getInstrInfo());
+  bool Modified = false;
+  for (auto &MBB : MF)
+    Modified |= expandMBB(MBB);
+  return Modified;
+}
+
+bool RISCVPostRAExpandPseudo::expandMBB(MachineBasicBlock &MBB) {
+  bool Modified = false;
+
+  MachineBasicBlock::iterator MBBI = MBB.begin(), E = MBB.end();
+  while (MBBI != E) {
+    MachineBasicBlock::iterator NMBBI = std::next(MBBI);
+    Modified |= expandMI(MBB, MBBI, NMBBI);
+    MBBI = NMBBI;
+  }
+
+  return Modified;
+}
+
+bool RISCVPostRAExpandPseudo::expandMI(MachineBasicBlock &MBB,
+                                       MachineBasicBlock::iterator MBBI,
+                                       MachineBasicBlock::iterator &NextMBBI) {
+  switch (MBBI->getOpcode()) {
+  case RISCV::PseudoMovImm:
+    return expandMovImm(MBB, MBBI);
+  default:
+    return false;
+  }
+}
+
+bool RISCVPostRAExpandPseudo::expandMovImm(MachineBasicBlock &MBB,
+                                           MachineBasicBlock::iterator MBBI) {
+  DebugLoc DL = MBBI->getDebugLoc();
+
+  int64_t Val = MBBI->getOperand(1).getImm();
+
+  RISCVMatInt::InstSeq Seq = RISCVMatInt::generateInstSeq(
+      Val, MBB.getParent()->getSubtarget().getFeatureBits());
+  assert(!Seq.empty());
+
+  Register SrcReg = RISCV::X0;
----------------
preames wrote:

This looks very close to RISCVInstrInfo::movImm, any chance we can common code?

https://github.com/llvm/llvm-project/pull/69983