ARM: Add tests for CopyBytes.

src/arm/macro-assembler-arm.cc

Index: src/arm/macro-assembler-arm.cc
diff --git a/src/arm/macro-assembler-arm.cc b/src/arm/macro-assembler-arm.cc
index 7628f23a5be9f137b24bc184bc7c2ba664f8ef5c..e1ff88e93f1bb8ca64809357203f0dfa23c7d17e 100644
--- a/src/arm/macro-assembler-arm.cc
+++ b/src/arm/macro-assembler-arm.cc
@@ -3186,37 +3186,52 @@ void MacroAssembler::CopyFields(Register dst,
   }
 }
 
-
 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));
+  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));
-  sub(length, length, Operand(1), SetCC);
-  b(ne, &byte_loop_1);
 
   // 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));
@@ -3225,8 +3240,8 @@ void MacroAssembler::CopyBytes(Register src,
     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.

@@ -3234,13 +3249,12 @@ void MacroAssembler::CopyBytes(Register src,
   b(eq, &done);
   bind(&byte_loop_1);
   ldrb(scratch, MemOperand(src, 1, PostIndex));
-  strb(scratch, MemOperand(dst, 1, PostIndex));
   sub(length, length, Operand(1), SetCC);
+  strb(scratch, MemOperand(dst, 1, PostIndex));
   b(ne, &byte_loop_1);
   bind(&done);
 }
 
-
 void MacroAssembler::InitializeFieldsWithFiller(Register start_offset,
                                                 Register end_offset,
                                                 Register filler) {