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      1 // Copyright 2013, ARM Limited
      2 // All rights reserved.
      3 //
      4 // Redistribution and use in source and binary forms, with or without
      5 // modification, are permitted provided that the following conditions are met:
      6 //
      7 //   * Redistributions of source code must retain the above copyright notice,
      8 //     this list of conditions and the following disclaimer.
      9 //   * Redistributions in binary form must reproduce the above copyright notice,
     10 //     this list of conditions and the following disclaimer in the documentation
     11 //     and/or other materials provided with the distribution.
     12 //   * Neither the name of ARM Limited nor the names of its contributors may be
     13 //     used to endorse or promote products derived from this software without
     14 //     specific prior written permission.
     15 //
     16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND
     17 // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     18 // WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     19 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
     20 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     21 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     22 // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
     23 // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     24 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     25 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26 
     27 #include "examples.h"
     28 
     29 #define BUF_SIZE (4096)
     30 #define __ masm->
     31 
     32 void GenerateSwapInt32(MacroAssembler* masm) {
     33   {
     34     // In this scope the register x2 will be used by the macro-assembler
     35     // as the stack pointer (via peek, poke, push, etc).
     36     const Register old_stack_pointer = __ StackPointer();
     37     __ Mov(x2, __ StackPointer());
     38     __ SetStackPointer(x2);
     39 
     40     // This call to Claim is not 16-byte aligned and would have failed
     41     // if the current stack pointer was sp.
     42     __ Claim(8);
     43 
     44     __ Poke(w0, 0);
     45     __ Poke(w1, 4);
     46     __ Peek(w1, 0);
     47     __ Peek(w0, 4);
     48 
     49     __ Drop(8);
     50 
     51     // Even if we didn't use the system stack pointer, sp might have been
     52     // modified because the ABI forbids access to memory below the stack
     53     // pointer.
     54     __ Mov(old_stack_pointer, __ StackPointer());
     55     __ SetStackPointer(old_stack_pointer);
     56   }
     57 
     58   // The stack pointer has now been switched back to sp.
     59   __ Ret();
     60 }
     61 
     62 
     63 #ifndef TEST_EXAMPLES
     64 int main(void) {
     65   // Create and initialize the assembler and the simulator.
     66   byte assm_buf[BUF_SIZE];
     67   MacroAssembler masm(assm_buf, BUF_SIZE);
     68   Decoder decoder;
     69   Simulator simulator(&decoder);
     70 
     71   // Generate the code for the example function.
     72   Label swap_int32;
     73   masm.Bind(&swap_int32);
     74   GenerateSwapInt32(&masm);
     75   masm.FinalizeCode();
     76 
     77   // Run the example function.
     78   simulator.set_wreg(0, 0x11111111);
     79   simulator.set_wreg(1, 0x22222222);
     80 
     81   printf("Before swap_int32:\n"
     82          "x0 = 0x%" PRIx32 "\n"
     83          "x1 = 0x%" PRIx32 "\n",
     84          simulator.wreg(0), simulator.wreg(1));
     85 
     86   simulator.RunFrom(swap_int32.target());
     87 
     88   printf("After swap_int32:\n"
     89          "x0 = 0x%" PRIx32 "\n"
     90          "x1 = 0x%" PRIx32 "\n",
     91          simulator.wreg(0), simulator.wreg(1));
     92 
     93   return 0;
     94 }
     95 #endif
     96