ARM: Add tests for CopyBytes.

src/arm/macro-assembler-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3168 matching lines @@
 
   int remain = field_count % (DwVfpRegister::kSizeInBytes / kPointerSize);
   if (remain != 0) {
     vldr(double_scratch.low(),
          FieldMemOperand(src, (field_count - 1) * kPointerSize));
     vstr(double_scratch.low(),
          FieldMemOperand(dst, (field_count - 1) * kPointerSize));
   }
 }
 
-
 void MacroAssembler::CopyBytes(Register src,
                                Register dst,
                                Register length,
                                Register scratch) {
-  Label align_loop, align_loop_1, word_loop, byte_loop, byte_loop_1, done;
+  Label word_loop, byte_loop, byte_loop_1, done;
+

[Benedikt Meurer, 2013/09/03 11:54:35]

Please add ASSERTs that src, dst, length and scratch are distinct registers.

+  cmp(length, Operand(8));
+  b(lt, &byte_loop);
 
   // Align src before copying in word size chunks.
-  bind(&align_loop);
-  cmp(length, Operand::Zero());
-  b(eq, &done);
-  bind(&align_loop_1);
   tst(src, Operand(kPointerSize - 1));

[Rodolph Perfetta, 2013/09/03 14:47:07]

This code could be improve further, see the tail end of the copy in
codegen-arm.cc:CreateMemCopyUint8Function.

   b(eq, &word_loop);
+
   ldrb(scratch, MemOperand(src, 1, PostIndex));
+  sub(length, length, Operand(1));
+  tst(src, Operand(kPointerSize - 1));
   strb(scratch, MemOperand(dst, 1, PostIndex));
-  sub(length, length, Operand(1), SetCC);
-  b(ne, &byte_loop_1);
+  b(eq, &word_loop);
+
+  ldrb(scratch, MemOperand(src, 1, PostIndex));
+  sub(length, length, Operand(1));
+  tst(src, Operand(kPointerSize - 1));
+  strb(scratch, MemOperand(dst, 1, PostIndex));
+  b(eq, &word_loop);
+
+  ldrb(scratch, MemOperand(src, 1, PostIndex));
+  sub(length, length, Operand(1));
+  strb(scratch, MemOperand(dst, 1, PostIndex));
 
   // Copy bytes in word size chunks.
   bind(&word_loop);
-  if (emit_debug_code()) {
-    tst(src, Operand(kPointerSize - 1));
-    Assert(eq, kExpectingAlignmentForCopyBytes);
-  }
-  cmp(length, Operand(kPointerSize));
-  b(lt, &byte_loop);
-  ldr(scratch, MemOperand(src, kPointerSize, PostIndex));
+
   if (CpuFeatures::IsSupported(UNALIGNED_ACCESSES)) {
+    ldr(scratch, MemOperand(src, kPointerSize, PostIndex));
+    sub(length, length, Operand(kPointerSize));
+    cmp(length, Operand(kPointerSize));
     str(scratch, MemOperand(dst, kPointerSize, PostIndex));
   } else {
+    if (emit_debug_code()) {
+      tst(src, Operand(kPointerSize - 1));
+      Assert(eq, kExpectingAlignmentForCopyBytes);
+    }
+    cmp(length, Operand(kPointerSize));
+    b(lt, &byte_loop);
+    ldr(scratch, MemOperand(src, kPointerSize, PostIndex));
+    sub(length, length, Operand(kPointerSize));
     strb(scratch, MemOperand(dst, 1, PostIndex));
     mov(scratch, Operand(scratch, LSR, 8));
     strb(scratch, MemOperand(dst, 1, PostIndex));
     mov(scratch, Operand(scratch, LSR, 8));
     strb(scratch, MemOperand(dst, 1, PostIndex));
     mov(scratch, Operand(scratch, LSR, 8));
     strb(scratch, MemOperand(dst, 1, PostIndex));
   }
-  sub(length, length, Operand(kPointerSize));
-  b(&word_loop);
+
+  b(ge, &word_loop);
 
   // Copy the last bytes if any left.
   bind(&byte_loop);

[Rodolph Perfetta, 2013/09/03 14:47:07]

here too you could avoid the small loop.

   cmp(length, Operand::Zero());
   b(eq, &done);
   bind(&byte_loop_1);
   ldrb(scratch, MemOperand(src, 1, PostIndex));
+  sub(length, length, Operand(1), SetCC);
   strb(scratch, MemOperand(dst, 1, PostIndex));
-  sub(length, length, Operand(1), SetCC);
   b(ne, &byte_loop_1);
   bind(&done);
 }
 
-
 void MacroAssembler::InitializeFieldsWithFiller(Register start_offset,
                                                 Register end_offset,
                                                 Register filler) {
   Label loop, entry;
   b(&entry);
   bind(&loop);
   str(filler, MemOperand(start_offset, kPointerSize, PostIndex));
   bind(&entry);
   cmp(start_offset, end_offset);
   b(lt, &loop);
@@ skipping 625 matching lines @@
 void CodePatcher::EmitCondition(Condition cond) {
   Instr instr = Assembler::instr_at(masm_.pc_);
   instr = (instr & ~kCondMask) | cond;
   masm_.emit(instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM