[mips][microMIPS] Implement BGEZALS and BLTZALS instructions

[jkolek]

Summary

Implement microMIPS branch instructions BGEZALS and BLTZALS with short delay slot.

[dsanders]

LGTM with a nit

lib/Target/Mips/MicroMipsInstrInfo.td

119

Nit: It's not very clear what the zero refers to in 'BranchZeroLinkMM'. Would 'BranchCompareToZeroLinkMM' be better?

[jkolek]

The class 'BranchZeroLinkMM' has been renamed to 'BranchCompareToZeroLinkMM'.

Closed by commit rL217678 (authored by zjovanovic).

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

   switch (Opcode) {
     case Mips::JALS_MM:
     case Mips::JALRS_MM:
+    case Mips::BGEZALS_MM:
+    case Mips::BLTZALS_MM:
       return true;
     default:
       return false;

lib/Target/Mips/MicroMipsInstrInfo.td

   class JumpLinkRegMM<string opstr, RegisterOperand RO>:
     InstSE<(outs RO:$rd), (ins RO:$rs), !strconcat(opstr, "\t$rd, $rs"),
             [], IIBranch, FrmR>;
+
+  class BranchZeroLinkMM<string opstr, DAGOperand opnd, RegisterOperand RO> :
+    InstSE<(outs), (ins RO:$rs, opnd:$offset),
+           !strconcat(opstr, "\t$rs, $offset"), [], IIBranch, FrmI, opstr>;
 }
 
 def MFHI16_MM : MoveFromHILOMM<"mfhi", GPR32Opnd, AC0>, MFHILO_FM_MM16<0x10>;

   def BLTZAL_MM : MMRel, BGEZAL_FT<"bltzal", brtarget_mm, GPR32Opnd>,
                   BGEZAL_FM_MM<0x01>;
 
+  /// Branch Instructions - Short Delay Slot
+  def BGEZALS_MM : BranchZeroLinkMM<"bgezals", brtarget_mm, GPR32Opnd>,
+                   BGEZAL_FM_MM<0x13>;
+  def BLTZALS_MM : BranchZeroLinkMM<"bltzals", brtarget_mm, GPR32Opnd>,
+                   BGEZAL_FM_MM<0x11>;
+
   /// Control Instructions
   def SYNC_MM    : MMRel, SYNC_FT<"sync">, SYNC_FM_MM;
   def BREAK_MM   : MMRel, BRK_FT<"break">, BRK_FM_MM;

test/MC/Mips/micromips-branch-instructions.s

 # CHECK-EL: nop                  # encoding: [0x00,0x00,0x00,0x00]
 # CHECK-EL: bltz $6, 1332        # encoding: [0x06,0x40,0x9a,0x02]
 # CHECK-EL: nop                  # encoding: [0x00,0x00,0x00,0x00]
+# CHECK-EL: bgezals $6, 1332     # encoding: [0x66,0x42,0x9a,0x02]
+# CHECK-EL: move $zero, $zero    # encoding: [0x00,0x0c]
+# CHECK-EL: bltzals $6, 1332     # encoding: [0x26,0x42,0x9a,0x02]
+# CHECK-EL: move $zero, $zero    # encoding: [0x00,0x0c]
 #------------------------------------------------------------------------------
 # Big endian
 #------------------------------------------------------------------------------

 # CHECK-EB: nop                  # encoding: [0x00,0x00,0x00,0x00]
 # CHECK-EB: bltz $6, 1332        # encoding: [0x40,0x06,0x02,0x9a]
 # CHECK-EB: nop                  # encoding: [0x00,0x00,0x00,0x00]
+# CHECK-EB: bgezals $6, 1332     # encoding: [0x42,0x66,0x02,0x9a]
+# CHECK-EB: move $zero, $zero    # encoding: [0x0c,0x00]
+# CHECK-EB: bltzals $6, 1332     # encoding: [0x42,0x26,0x02,0x9a]
+# CHECK-EB: move $zero, $zero    # encoding: [0x0c,0x00]
 
      b      1332
      beq    $9,$6,1332

      bne    $9,$6,1332
      bal    1332
      bltz   $6,1332
+     bgezals $6,1332
+     bltzals $6,1332