[llvm] Adding support in llvm-exegesis for Aarch64 for handling FPR64/128, PPR16 and ZPR128 reg class. (PR #127564)

[David Green via llvm-commits]

================
@@ -35,6 +35,48 @@ static MCInst loadImmediate(MCRegister Reg, unsigned RegBitWidth,
       .addImm(Value.getZExtValue());
 }
 
+static MCInst loadZPRImmediate(MCRegister Reg, unsigned RegBitWidth,
+                               const APInt &Value) {
+  if (Value.getBitWidth() > RegBitWidth)
+    llvm_unreachable("Value must fit in the ZPR Register");
+  // For ZPR, we typically use DUPM instruction to load immediate values
+  return MCInstBuilder(AArch64::DUPM_ZI)
+      .addReg(Reg)
+      .addImm(Value.getZExtValue());
+}
+
+static MCInst loadPPRImmediate(MCRegister Reg, unsigned RegBitWidth,
+                               const APInt &Value) {
+  if (Value.getBitWidth() > RegBitWidth)
+    llvm_unreachable("Value must fit in the PPR Register");
+  // For PPR, we typically use PTRUE instruction to set predicate registers
+  return MCInstBuilder(AArch64::PTRUE_B)
+      .addReg(Reg)
+      .addImm(31); // All lanes true
+}
+
+// Generates instruction to load an FP immediate value into a register.
+static unsigned getLoadFPImmediateOpcode(unsigned RegBitWidth) {
+  switch (RegBitWidth) {
+  case 64:
+    return AArch64::FMOVDi; 
+  case 128:
+    return AArch64::MOVIv2d_ns;
+  }
+  llvm_unreachable("Invalid Value Width");
+}
+
+
+// Generates instruction to load an FP immediate value into a register.
+static MCInst loadFPImmediate(MCRegister Reg, unsigned RegBitWidth,
+                            const APInt &Value) {
+  if (Value.getBitWidth() > RegBitWidth)
+    llvm_unreachable("Value must fit in the FP Register");
+  return MCInstBuilder(getLoadFPImmediateOpcode(RegBitWidth))
----------------
davemgreen wrote:

For the adds with immediates - They can work through OPERAND_IMMEDIATE but that isn't set for a lot of operands. 1ae4726ba24de0b23a312b53fa9993ad9d5d166c was related once upon a time. Ideally tablegen would understand the valid ranges for the immediate operands so that it could generate valid values (and then that would be useful elsewhere in checking that the instructions are valid).

https://github.com/llvm/llvm-project/pull/127564