[llvm] [RISCV] Macro-fusion support for veyron-v1 CPU. (PR #70012)

[Craig Topper via llvm-commits]

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@@ -18,6 +18,101 @@
 
 using namespace llvm;
 
+static bool checkRegisters(Register FirstDest, const MachineInstr &SecondMI) {
+  if (!SecondMI.getOperand(1).isReg())
+    return false;
+
+  if (SecondMI.getOperand(1).getReg() != FirstDest)
+    return false;
+
+  // If the input is virtual make sure this is the only user.
+  if (FirstDest.isVirtual()) {
+    auto &MRI = SecondMI.getMF()->getRegInfo();
+    return MRI.hasOneNonDBGUse(FirstDest);
+  }
+
+  return SecondMI.getOperand(0).getReg() == FirstDest;
+}
+
+// Fuse load with add:
+// add rd, rs1, rs2
+// ld rd, 0(rd)
+static bool isLDADD(const MachineInstr *FirstMI, const MachineInstr &SecondMI) {
+  if (SecondMI.getOpcode() != RISCV::LD)
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topperc wrote:

@mgudim Is this fusion reall restricted to just 64-bit load?

https://github.com/llvm/llvm-project/pull/70012