void Thumb2Assembler::EmitLoadStore()

in compiler/utils/arm/assembler_thumb2.cc [2322:2482]
133 lines of code
43 McCabe index (conditional complexity)

void Thumb2Assembler::EmitLoadStore(Condition cond,
                                    bool load,
                                    bool byte,
                                    bool half,
                                    bool is_signed,
                                    Register rd,
                                    const Address& ad) {
  CHECK_NE(rd, kNoRegister);
  CheckCondition(cond);
  bool must_be_32bit = force_32bit_;
  if (IsHighRegister(rd)) {
    must_be_32bit = true;
  }

  Register rn = ad.GetRegister();
  if (IsHighRegister(rn) && rn != SP && rn != PC) {
    must_be_32bit = true;
  }

  if (is_signed || ad.GetOffset() < 0 || ad.GetMode() != Address::Offset) {
    must_be_32bit = true;
  }

  if (ad.IsImmediate()) {
    // Immediate offset
    int32_t offset = ad.GetOffset();

    // The 16 bit SP relative instruction can only have a 10 bit offset.
    if (rn == SP && offset >= (1 << 10)) {
      must_be_32bit = true;
    }

    if (byte) {
      // 5 bit offset, no shift.
      if (offset >= (1 << 5)) {
        must_be_32bit = true;
      }
    } else if (half) {
      // 6 bit offset, shifted by 1.
      if (offset >= (1 << 6)) {
        must_be_32bit = true;
      }
    } else {
      // 7 bit offset, shifted by 2.
      if (offset >= (1 << 7)) {
        must_be_32bit = true;
      }
    }

    if (must_be_32bit) {
      int32_t encoding = B31 | B30 | B29 | B28 | B27 |
          (load ? B20 : 0) |
          (is_signed ? B24 : 0) |
          static_cast<uint32_t>(rd) << 12 |
          ad.encodingThumb(true) |
          (byte ? 0 : half ? B21 : B22);
      Emit32(encoding);
    } else {
      // 16 bit thumb1.
      uint8_t opA = 0;
      bool sp_relative = false;

      if (byte) {
        opA = 7U /* 0b0111 */;
      } else if (half) {
        opA = 8U /* 0b1000 */;
      } else {
        if (rn == SP) {
          opA = 9U /* 0b1001 */;
          sp_relative = true;
        } else {
          opA = 6U /* 0b0110 */;
        }
      }
      int16_t encoding = opA << 12 |
          (load ? B11 : 0);

      CHECK_GE(offset, 0);
      if (sp_relative) {
        // SP relative, 10 bit offset.
        CHECK_LT(offset, (1 << 10));
        CHECK_ALIGNED(offset, 4);
        encoding |= rd << 8 | offset >> 2;
      } else {
        // No SP relative.  The offset is shifted right depending on
        // the size of the load/store.
        encoding |= static_cast<uint32_t>(rd);

        if (byte) {
          // 5 bit offset, no shift.
          CHECK_LT(offset, (1 << 5));
        } else if (half) {
          // 6 bit offset, shifted by 1.
          CHECK_LT(offset, (1 << 6));
          CHECK_ALIGNED(offset, 2);
          offset >>= 1;
        } else {
          // 7 bit offset, shifted by 2.
          CHECK_LT(offset, (1 << 7));
          CHECK_ALIGNED(offset, 4);
          offset >>= 2;
        }
        encoding |= rn << 3 | offset  << 6;
      }

      Emit16(encoding);
    }
  } else {
    // Register shift.
    if (ad.GetRegister() == PC) {
       // PC relative literal encoding.
      int32_t offset = ad.GetOffset();
      if (must_be_32bit || offset < 0 || offset >= (1 << 10) || !load) {
        int32_t up = B23;
        if (offset < 0) {
          offset = -offset;
          up = 0;
        }
        CHECK_LT(offset, (1 << 12));
        int32_t encoding = 0x1f << 27 | 0xf << 16 | B22 | (load ? B20 : 0) |
            offset | up |
            static_cast<uint32_t>(rd) << 12;
        Emit32(encoding);
      } else {
        // 16 bit literal load.
        CHECK_GE(offset, 0);
        CHECK_LT(offset, (1 << 10));
        int32_t encoding = B14 | (load ? B11 : 0) | static_cast<uint32_t>(rd) << 8 | offset >> 2;
        Emit16(encoding);
      }
    } else {
      if (ad.GetShiftCount() != 0) {
        // If there is a shift count this must be 32 bit.
        must_be_32bit = true;
      } else if (IsHighRegister(ad.GetRegisterOffset())) {
        must_be_32bit = true;
      }

      if (must_be_32bit) {
        int32_t encoding = 0x1f << 27 | (load ? B20 : 0) | static_cast<uint32_t>(rd) << 12 |
            ad.encodingThumb(true);
        if (half) {
          encoding |= B21;
        } else if (!byte) {
          encoding |= B22;
        }
        Emit32(encoding);
      } else {
        // 16 bit register offset.
        int32_t encoding = B14 | B12 | (load ? B11 : 0) | static_cast<uint32_t>(rd) |
            ad.encodingThumb(false);
        if (byte) {
          encoding |= B10;
        } else if (half) {
          encoding |= B9;
        }
        Emit16(encoding);
      }
    }
  }
}