[PATCH] ARM IAS: support GNU extension for ldrd, strd

[Saleem Abdulrasool]

Hi rengolin, t.p.northover,

The GNU assembler has an extension that allows for the elision of the paired
register (dt2) for the LDRD and STRD mnemonics.  Add support for this in the
assembly parser.  Canonicalise the usage during the instruction parsing from
the specified version.



http://llvm-reviews.chandlerc.com/D2512

Files:
  lib/Target/ARM/ARMInstrInfo.td
  lib/Target/ARM/AsmParser/ARMAsmParser.cpp
  test/MC/ARM/arm-memory-instructions.s

Index: lib/Target/ARM/ARMInstrInfo.td
===================================================================
--- lib/Target/ARM/ARMInstrInfo.td
+++ lib/Target/ARM/ARMInstrInfo.td
@@ -2278,6 +2278,11 @@
   def LDRD : AI3ld<0b1101, 0, (outs GPR:$Rt, GPR:$Rt2), (ins addrmode3:$addr),
                    LdMiscFrm, IIC_iLoad_d_r, "ldrd", "\t$Rt, $Rt2, $addr", []>,
              Requires<[IsARM, HasV5TE]>;
+
+  let isAsmParserOnly = 1 in
+    def LDRD_PAIR : AI3ld<0b1101, 0, (outs GPRPairOp:$Rt), (ins addrmode3:$addr),
+                          LdMiscFrm, IIC_iLoad_d_r, "ldrd", "\t$Rt, $addr", []>,
+                    Requires<[IsARM, HasV5TE]>;
 }
 
 def LDA : AIldracq<0b00, (outs GPR:$Rt), (ins addr_offset_none:$addr),
@@ -2533,13 +2538,21 @@
                [(truncstorei16 GPR:$Rt, addrmode3:$addr)]>;
 
 // Store doubleword
-let mayStore = 1, neverHasSideEffects = 1, hasExtraSrcRegAllocReq = 1 in
+let mayStore = 1, neverHasSideEffects = 1, hasExtraSrcRegAllocReq = 1 in {
   def STRD : AI3str<0b1111, (outs), (ins GPR:$Rt, GPR:$Rt2, addrmode3:$addr),
                     StMiscFrm, IIC_iStore_d_r, "strd", "\t$Rt, $Rt2, $addr", []>,
              Requires<[IsARM, HasV5TE]> {
     let Inst{21} = 0;
   }
 
+  let isAsmParserOnly = 1 in
+    def STRD_PAIR : AI3str<0b1111, (outs), (ins GPRPairOp:$Rt, addrmode3:$addr),
+                           StMiscFrm, IIC_iStore_d_r, "strd", "\t$Rt, $addr", []>,
+                    Requires<[IsARM, HasV5TE]> {
+      let Inst{21} = 0;
+    }
+}
+
 // Indexed stores
 multiclass AI2_stridx<bit isByte, string opc,
                       InstrItinClass iii, InstrItinClass iir> {
Index: lib/Target/ARM/AsmParser/ARMAsmParser.cpp
===================================================================
--- lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -5391,6 +5391,18 @@
     }
   }
 
+  if ((Mnemonic == "ldrd" || Mnemonic == "strd") && !isThumb() &&
+      Operands.size() == 4) {
+    ARMOperand *Op = static_cast<ARMOperand *>(Operands[2]);
+    assert(Op->isReg() && "expected register argument");
+    assert(MRI->getMatchingSuperReg(Op->getReg(), ARM::gsub_0,
+                                    &MRI->getRegClass(ARM::GPRPairRegClassID))
+           && "expected register pair");
+    Operands.insert(Operands.begin() + 3,
+                    ARMOperand::CreateReg(Op->getReg() + 1, Op->getStartLoc(),
+                                          Op->getEndLoc()));
+  }
+
   // FIXME: As said above, this is all a pretty gross hack.  This instruction
   // does not fit with other "subs" and tblgen.
   // Adjust operands of B9.3.19 SUBS PC, LR, #imm (Thumb2) system instruction
@@ -8654,6 +8666,11 @@
         return Match_Success;
     }
     break;
+  case MCK_GPRPair:
+    if (Op->isReg() &&
+        MRI->getRegClass(ARM::GPRRegClassID).contains(Op->getReg()))
+      return Match_Success;
+    break;
   }
   return Match_InvalidOperand;
 }
Index: test/MC/ARM/arm-memory-instructions.s
===================================================================
--- test/MC/ARM/arm-memory-instructions.s
+++ test/MC/ARM/arm-memory-instructions.s
@@ -485,3 +485,14 @@
 @ CHECK: strht	r8, [r1], #-25          @ encoding: [0xb9,0x81,0x61,0xe0]
 @ CHECK: strht	r5, [r3], r4            @ encoding: [0xb4,0x50,0xa3,0xe0]
 @ CHECK: strht	r6, [r8], -r0           @ encoding: [0xb0,0x60,0x28,0xe0]
+
+ at ------------------------------------------------------------------------------
+@ GNU Assembler Compatibility
+ at ------------------------------------------------------------------------------
+
+	ldrd r0, [sp]
+	strd r0, [sp]
+
+@ CHECK: ldrd r0, r1, [sp]              @ encoding: [0xd0,0x00,0xcd,0xe1]
+@ CHECK: strd r0, r1, [sp]              @ encoding: [0xf0,0x00,0xcd,0xe1]
+
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