[mips][microMIPSr6] Implement disassembler support

[jkolek]

Summary

This patch implements disassembler support for microMIPS32r6.

[dsanders]

lib/Target/Mips/Disassembler/MipsDisassembler.cpp

34–35 ↗

(On Diff #22370)

I'd prefer not to cache flag values from MCSubtargetInfo. Could you do this the way hasMips32r6() does it instead?

I'd appreciate it if you could switch IsMicroMips to that style too (in a separate patch)

[dsanders]

LGTM

[dsanders]

Sorry, I think I missed something.

lib/Target/Mips/Disassembler/MipsDisassembler.cpp

828 ↗

(On Diff #22572)

Do we need both here? I'd expect IsMicroMips to be true when hasMicroMips32r6() is true. It may be better to move the hasMicroMips32r6() check to the else on line 849.

llvm/trunk/lib/Target/Mips/Disassembler/MipsDisassembler.cpp

if (Result != MCDisassembler::Fail) {
       Size = 2;
       return Result;
     }
 
     Result = readInstruction32(Bytes, Address, Size, Insn, IsBigEndian, true);
     if (Result == MCDisassembler::Fail)
       return MCDisassembler::Fail;
 
+    if (hasMips32r6()) {
+      DEBUG(dbgs() << "Trying MicroMips32r632 table (32-bit instructions):\n");
+      // Calling the auto-generated decoder function.
+      Result = decodeInstruction(DecoderTableMicroMips32r632, Instr, Insn, Address,
+                                 this, STI);
+    } else {
       DEBUG(dbgs() << "Trying MicroMips32 table (32-bit instructions):\n");
       // Calling the auto-generated decoder function.
       Result = decodeInstruction(DecoderTableMicroMips32, Instr, Insn, Address,
                                  this, STI);
+    }
     if (Result != MCDisassembler::Fail) {
       Size = 4;
       return Result;
     }
     return MCDisassembler::Fail;
   }
 
   Result = readInstruction32(Bytes, Address, Size, Insn, IsBigEndian, false);

llvm/trunk/lib/Target/Mips/MicroMips32r6InstrInfo.td

 class BC_MMR6_DESC : BC_MMR6_DESC_BASE<"bc", brtarget26>;
 
 //===----------------------------------------------------------------------===//
 //
 // Instruction Definitions
 //
 //===----------------------------------------------------------------------===//
 
+let DecoderNamespace = "MicroMips32r6" in {
 def BALC_MMR6 : R6MMR6Rel, BALC_MMR6_ENC, BALC_MMR6_DESC, ISA_MICROMIPS32R6;
 def BC_MMR6 : R6MMR6Rel, BC_MMR6_ENC, BC_MMR6_DESC, ISA_MICROMIPS32R6;
+}

llvm/trunk/test/MC/Disassembler/Mips/micromips32r6.txt

+# RUN: llvm-mc --disassemble %s -triple=mips-unknown-linux -mcpu=mips32r6 -mattr=micromips | FileCheck %s
+
+# CHECK: balc 14572256
+0xb4 0x37 0x96 0xb8
+
+# CHECK: bc 14572256
+0x94 0x37 0x96 0xb8