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

[via llvm-commits]

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@@ -28,13 +28,66 @@ static unsigned getLoadImmediateOpcode(unsigned RegBitWidth) {
 // Generates instruction to load an immediate value into a register.
 static MCInst loadImmediate(MCRegister Reg, unsigned RegBitWidth,
                             const APInt &Value) {
-  if (Value.getBitWidth() > RegBitWidth)
-    llvm_unreachable("Value must fit in the Register");
+  // 0 <= Value.getZExtValue() < 2**16
+  assert(Value.getZExtValue() < (1 << 16) &&
+         "Value must be in the range of the immediate opcode");
   return MCInstBuilder(getLoadImmediateOpcode(RegBitWidth))
       .addReg(Reg)
       .addImm(Value.getZExtValue());
 }
 
+static MCInst loadZPRImmediate(MCRegister Reg, unsigned RegBitWidth,
+                               const APInt &Value) {
+  // 0 <= Value.getZExtValue() < 2**13
+  assert(Value.getZExtValue() < (1 << 13) &&
+         "Value must be in the range of the immediate opcode");
+  // 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) {
+  // For PPR, we typically use PTRUE instruction to set predicate registers
+  return MCInstBuilder(AArch64::PTRUE_B)
+      .addReg(Reg)
+      .addImm(31); // All lanes true for 16 bits
+}
+
+// Fetch base-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) {
+  // -31 <= Value.getZExtValue() <= 31
+  assert(Value.getZExtValue() <= 31 &&
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lakshayk-nv wrote:

> Can this use a DUP_ZI and check the value is -128 to 127?
>>
Updated the `loadZPRImmediate()` to use `DUP_ZI_D` base instruction and range assert and corresponding disassembly check in test file.

> just check that the Value == 0
>>
Added assert for `Value == 0` and used `MOVID` base instruction for FPR64, thus check is in disassembly is for `0` only.

Thanks!

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