Add "add immediate" instruction to the ARM integrated assembler.

src/IceAssemblerARM32.cpp

 //===- subzero/src/IceAssemblerARM32.cpp - Assembler for ARM32 --*- C++ -*-===//
 //
 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // Modified by the Subzero authors.
 //
 //===----------------------------------------------------------------------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
 /// This file implements the Assembler class for ARM32.
 ///
 //===----------------------------------------------------------------------===//
 
 #include "IceAssemblerARM32.h"
 
-namespace Ice {
+namespace {
+
+using namespace Ice;
 
 // The following define individual bits.
 static constexpr uint32_t B0 = 1;
 static constexpr uint32_t B2 = 1 << 2;
 static constexpr uint32_t B3 = 1 << 3;
 static constexpr uint32_t B4 = 1 << 4;
 static constexpr uint32_t B5 = 1 << 5;
 static constexpr uint32_t B6 = 1 << 6;
 static constexpr uint32_t B21 = 1 << 21;
 static constexpr uint32_t B24 = 1 << 24;
 
 // Constants used for the decoding or encoding of the individual fields of
 // instructions. Based on ARM section A5.1.
 static constexpr uint32_t kConditionShift = 28;
 static constexpr uint32_t kOpcodeShift = 21;
 static constexpr uint32_t kRdShift = 12;
 static constexpr uint32_t kRmShift = 0;
 static constexpr uint32_t kRnShift = 16;
 static constexpr uint32_t kSShift = 20;
 static constexpr uint32_t kTypeShift = 25;
 
 // Immediate instruction fields encoding.
 static constexpr uint32_t kImmed8Bits = 8;
 static constexpr uint32_t kImmed8Shift = 0;
 static constexpr uint32_t kRotateBits = 4;
 static constexpr uint32_t kRotateShift = 8;
 
-// Types of instructions.
-static constexpr uint32_t kInstTypeImmediate = 1;
-
 inline uint32_t encodeBool(bool b) { return b ? 1 : 0; }
 
 inline uint32_t encodeGPRRegister(RegARM32::GPRRegister Rn) {
   return static_cast<uint32_t>(Rn);
 }
 
 inline bool isGPRRegisterDefined(RegARM32::GPRRegister R) {
   return R != RegARM32::Encoded_Not_GPR;
 }
 
 inline bool isGPRRegisterDefined(uint32_t R) {
   return R != encodeGPRRegister(RegARM32::Encoded_Not_GPR);
 }
 
 inline bool isConditionDefined(CondARM32::Cond Cond) {
   return Cond != CondARM32::kNone;
 }
 
 inline uint32_t encodeCondition(CondARM32::Cond Cond) {
   return static_cast<uint32_t>(Cond);
 }
 
-// Converts rotated immediate into imm12.
-inline uint32_t encodeImm12FromFlexImm(const OperandARM32FlexImm &FlexImm) {
-  uint32_t Immed8 = FlexImm.getImm();
-  uint32_t Rotate = FlexImm.getRotateAmt();
-  assert((Rotate < (1 << kRotateBits)) && (Immed8 < (1 << kImmed8Bits)));
-  return (Rotate << kRotateShift) | (Immed8 << kImmed8Shift);
+// The way an operand was decoded in function decode below.
+enum DecodedResult {
+  CantDecode = 0, // I.e. will fail in test.
+  DecodedAsRegister,
+  DecodedAsRotatedImm8
+};
+
+DecodedResult decode(const Ice::Operand *Operand, uint32_t &Value) {

[Jim Stichnoth, 2015/10/13 21:28:52]

Can you use Operand instead of Ice::Operand?

Also, maybe rename the arg Opnd instead of Operand to avoid a name conflict.

[Karl, 2015/10/13 21:39:25]

Done.

+  if (const auto *Var = llvm::dyn_cast<Variable>(Operand)) {
+    if (Var->hasReg()) {
+      Value = Var->getRegNum();
+      return DecodedAsRegister;
+    }
+  } else if (const auto *FlexImm =
+                 llvm::dyn_cast<OperandARM32FlexImm>(Operand)) {
+    uint32_t Immed8 = FlexImm->getImm();
+    uint32_t Rotate = FlexImm->getRotateAmt();
+    assert((Rotate < (1 << kRotateBits)) && (Immed8 < (1 << kImmed8Bits)));
+    Value = (Rotate << kRotateShift) | (Immed8 << kImmed8Shift);
+    return DecodedAsRotatedImm8;
+  }
+  return CantDecode;
 }
 
+} // end of anonymous namespace
+
+namespace Ice {
+
 Label *ARM32::AssemblerARM32::getOrCreateLabel(SizeT Number,
                                                LabelVector &Labels) {
   Label *L = nullptr;
   if (Number == Labels.size()) {
     L = new (this->allocate<Label>()) Label();
     Labels.push_back(L);
     return L;
   }
   if (Number > Labels.size()) {
     Labels.resize(Number + 1);
@@ skipping 17 matching lines @@
   }
   // TODO(kschimpf) Decide if we have near jumps.
   label->bindTo(bound);
 }
 
 void ARM32::AssemblerARM32::emitType01(CondARM32::Cond Cond, uint32_t Type,
                                        uint32_t Opcode, bool SetCc, uint32_t Rn,
                                        uint32_t Rd, uint32_t Imm12) {
   assert(isGPRRegisterDefined(Rd));
   assert(Cond != CondARM32::kNone);
+  AssemblerBuffer::EnsureCapacity ensured(&Buffer);
   uint32_t Encoding = encodeCondition(Cond) << kConditionShift |
                       (Type << kTypeShift) | (Opcode << kOpcodeShift) |
                       (encodeBool(SetCc) << kSShift) | (Rn << kRnShift) |
                       (Rd << kRdShift) | Imm12;
   emitInst(Encoding);
 }
 
+void ARM32::AssemblerARM32::add(const Operand *OpRd, const Operand *OpRn,
+                                const Operand *OpSrc1, bool SetFlags,
+                                CondARM32::Cond Cond) {
+  // Note: Loop is used so that we can short circuit using break;
+  do {
+    uint32_t Rd;
+    if (decode(OpRd, Rd) != DecodedAsRegister)
+      break;
+    uint32_t Rn;
+    if (decode(OpRn, Rn) != DecodedAsRegister)
+      break;
+    uint32_t Src1Value;
+    // TODO(kschimpf) Other possible decodings of add.
+    if (decode(OpSrc1, Src1Value) == DecodedAsRotatedImm8) {
+      // ADD (Immediate): See ARM section A8.8.5, rule A1.
+      // cccc0010100snnnnddddiiiiiiiiiiii where cccc=Cond, dddd=Rd, nnnn=Rn,
+      // s=SetFlags and iiiiiiiiiiii=Src1Value
+      if (!isConditionDefined(Cond) || (Rd == RegARM32::Reg_pc && SetFlags) ||
+          (Rn == RegARM32::Reg_lr) || (Rn == RegARM32::Reg_pc && SetFlags))
+        // Conditions of rule violated.
+        break;
+      uint32_t Add = B2; // 0100
+      uint32_t InstType = 1;
+      emitType01(Cond, InstType, Add, SetFlags, Rn, Rd, Src1Value);
+      return;
+    }
+  } while (0);
+  UnimplementedError(Ctx->getFlags());
+}
+
 void ARM32::AssemblerARM32::bkpt(uint16_t imm16) {
   AssemblerBuffer::EnsureCapacity ensured(&Buffer);
   uint32_t Encoding = (CondARM32::AL << kConditionShift) | B24 | B21 |
                       ((imm16 >> 4) << 8) | B6 | B5 | B4 | (imm16 & 0xf);
   emitInst(Encoding);
 }
 
 void ARM32::AssemblerARM32::bx(RegARM32::GPRRegister Rm, CondARM32::Cond Cond) {
   // cccc000100101111111111110001mmmm where mmmm=rm and cccc=Cond.
   // (ARM section A8.8.27, encoding A1).
   assert(isGPRRegisterDefined(Rm));
   assert(isConditionDefined(Cond));
   AssemblerBuffer::EnsureCapacity ensured(&Buffer);
   uint32_t Encoding = (encodeCondition(Cond) << kConditionShift) | B24 | B21 |
                       (0xfff << 8) | B4 | (encodeGPRRegister(Rm) << kRmShift);
   emitInst(Encoding);
 }
 
-void ARM32::AssemblerARM32::mov(RegARM32::GPRRegister Rd,
-                                const OperandARM32FlexImm &FlexImm,
+void ARM32::AssemblerARM32::mov(const Operand *OpRd, const Operand *OpSrc,
                                 CondARM32::Cond Cond) {
-  // cccc0011101s0000ddddiiiiiiiiiiii (ARM section A8.8.102, encoding A1)
-  assert(isConditionDefined(Cond));
-  AssemblerBuffer::EnsureCapacity ensured(&Buffer);
-  bool SetCc = false; // Note: We don't use movs in this assembler.
-  uint32_t Rn = 0;
-  uint32_t Mov = B3 | B2 | B0; // 1101.
-  emitType01(Cond, kInstTypeImmediate, Mov, SetCc, Rn, encodeGPRRegister(Rd),
-             encodeImm12FromFlexImm(FlexImm));
+  // Note: Loop is used so that we can short ciruit using break;
+  do {
+    uint32_t Rd;
+    if (decode(OpRd, Rd) != DecodedAsRegister)
+      break;
+    uint32_t Src;
+    // TODO(kschimpf) Handle other forms of mov.
+    if (decode(OpSrc, Src) == DecodedAsRotatedImm8) {
+      // cccc0011101s0000ddddiiiiiiiiiiii (ARM section A8.8.102, encoding A1)
+      // Note: We don't use movs in this assembler.
+      constexpr bool SetFlags = false;
+      if (!isConditionDefined(Cond) || (Rd == RegARM32::Reg_pc && SetFlags))
+        // Conditions of rule violated.
+        break;
+      uint32_t Rn = 0;
+      uint32_t Mov = B3 | B2 | B0; // 1101.
+      uint32_t InstType = 1;
+      emitType01(Cond, InstType, Mov, SetFlags, Rn, Rd, Src);
+      return;
+    }
+  } while (0);
+  UnimplementedError(Ctx->getFlags());
 }
 
 } // end of namespace Ice