ARM refactoring assembly parsing of memory address operands.

Memory operand parsing is a bit haphazzard at the moment, in no small part
due to the even more haphazzard representations of memory operands in the .td
files. Start cleaning that all up, at least a bit.

The addressing modes in the .td files will be being simplified to not be
so monolithic, especially with regards to immediate vs. register offsets
and post-indexed addressing. addrmode3 is on its way with this patch, for
example.

This patch is foundational to enable going back to smaller incremental patches
for the individual memory referencing instructions themselves. It does just
enough to get the basics in place and handle the "make check" regression tests
we already have.

Follow-up work will be fleshing out the details and adding more robust test
cases for the individual instructions, starting with ARM mode and moving from
there into Thumb and Thumb2.

llvm-svn: 136845

1 files changed, 23 insertions, 14 deletions

diff --git a/llvm/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp b/llvm/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp
index 8b22786843f..26716763cf4 100644
--- a/llvm/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp
+++ b/llvm/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp
@@ -1393,7 +1393,7 @@ static bool DisassembleLdStFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
     if (Opcode == ARM::LDRBi12 || Opcode == ARM::LDRi12 ||
         Opcode == ARM::STRBi12 || Opcode == ARM::STRi12) {
       // Disassemble the 12-bit immediate offset, which is the second operand in
-      // $addrmode_imm12 => (ops GPR:$base, i32imm:$offsimm).    
+      // $addrmode_imm12 => (ops GPR:$base, i32imm:$offsimm).
       int Offset = AddrOpcode == ARM_AM::add ? 1 * Imm12 : -1 * Imm12;
       MI.addOperand(MCOperand::CreateImm(Offset));
     } else {
@@ -1512,34 +1512,43 @@ static bool DisassembleLdStMiscFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
 
   // For reg/reg form, base reg is followed by +/- reg.
   // For immediate form, it is followed by +/- imm8.
-  // See also ARMAddressingModes.h (Addressing Mode #3).
   if (OpIdx + 1 >= NumOps)
     return false;
 
-  assert((OpInfo[OpIdx].RegClass == ARM::GPRRegClassID) &&
-         (OpInfo[OpIdx+1].RegClass < 0) &&
-         "Expect 1 reg operand followed by 1 imm operand");
-
-  ARM_AM::AddrOpc AddrOpcode = getUBit(insn) ? ARM_AM::add : ARM_AM::sub;
   unsigned IndexMode =
-                 (MCID.TSFlags & ARMII::IndexModeMask) >> ARMII::IndexModeShift;
+    (MCID.TSFlags & ARMII::IndexModeMask) >> ARMII::IndexModeShift;
+  ARM_AM::AddrOpc AddrOpcode = getUBit(insn) ? ARM_AM::add : ARM_AM::sub;
   if (getAM3IBit(insn) == 1) {
-    MI.addOperand(MCOperand::CreateReg(0));
+    // FIXME: Conditional while in the midst of refactoring addrmode3. Will
+    // go away entirely when the rest are converted.
+    if (Opcode != ARM::STRHTi && Opcode != ARM::LDRSBTi &&
+        Opcode != ARM::LDRHTi && Opcode != ARM::LDRSHTi) {
+      MI.addOperand(MCOperand::CreateReg(0));
+      ++OpIdx;
+    }
 
-    // Disassemble the 8-bit immediate offset.
+    // Disassemble the 8-bit immediate offset (postidx_imm8).
     unsigned Imm4H = (insn >> ARMII::ImmHiShift) & 0xF;
     unsigned Imm4L = insn & 0xF;
-    unsigned Offset = ARM_AM::getAM3Opc(AddrOpcode, (Imm4H << 4) | Imm4L,
-                                        IndexMode);
+    unsigned Offset;
+    // FIXME: Remove the 'else' once done w/ addrmode3 refactor.
+    if (Opcode == ARM::STRHTi || Opcode == ARM::LDRSBTi ||
+        Opcode == ARM::LDRHTi || Opcode == ARM::LDRSHTi)
+      Offset = (Imm4H << 4) | Imm4L | (getUBit(insn) << 8);
+    else
+      Offset = ARM_AM::getAM3Opc(AddrOpcode, (Imm4H << 4) | Imm4L,
+                                 IndexMode);
+
     MI.addOperand(MCOperand::CreateImm(Offset));
+    ++OpIdx;
   } else {
     // Disassemble the offset reg (Rm).
+    unsigned Offset = ARM_AM::getAM3Opc(AddrOpcode, 0);
     MI.addOperand(MCOperand::CreateReg(getRegisterEnum(B, ARM::GPRRegClassID,
                                                        decodeRm(insn))));
-    unsigned Offset = ARM_AM::getAM3Opc(AddrOpcode, 0, IndexMode);
     MI.addOperand(MCOperand::CreateImm(Offset));
+    OpIdx += 2;
   }
-  OpIdx += 2;
 
   return true;
 }