Out-of-line constant pool on Arm: Stage 1 - Free up r7 for use as constant pool pointer register

src/arm/full-codegen-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 3948 matching lines @@
   __ AssertString(r0);
 
   __ ldr(r0, FieldMemOperand(r0, String::kHashFieldOffset));
   __ IndexFromHash(r0, r0);
 
   context()->Plug(r0);
 }
 
 
 void FullCodeGenerator::EmitFastAsciiArrayJoin(CallRuntime* expr) {
-  Label bailout, done, one_char_separator, long_separator,
-      non_trivial_array, not_size_one_array, loop,
+  Label bailout, pop_and_bailout, done, one_char_separator,
+      long_separator, non_trivial_array, not_size_one_array, loop,
       empty_separator_loop, one_char_separator_loop,
       one_char_separator_loop_entry, long_separator_loop;
   ZoneList<Expression*>* args = expr->arguments();
   ASSERT(args->length() == 2);
   VisitForStackValue(args->at(1));
   VisitForAccumulatorValue(args->at(0));
 
   // All aliases of the same register have disjoint lifetimes.
   Register array = r0;
   Register elements = no_reg;  // Will be r0.
   Register result = no_reg;  // Will be r0.
   Register separator = r1;
   Register array_length = r2;
   Register result_pos = no_reg;  // Will be r2
   Register string_length = r3;
   Register string = r4;
   Register element = r5;
   Register elements_end = r6;
-  Register scratch1 = r7;
-  Register scratch2 = r9;
+  Register scratch = r9;
 
   // Separator operand is on the stack.
   __ pop(separator);
 
   // Check that the array is a JSArray.
   __ JumpIfSmi(array, &bailout);
-  __ CompareObjectType(array, scratch1, scratch2, JS_ARRAY_TYPE);
+  __ CompareObjectType(array, scratch, array_length, JS_ARRAY_TYPE);
   __ b(ne, &bailout);
 
   // Check that the array has fast elements.
-  __ CheckFastElements(scratch1, scratch2, &bailout);
+  __ CheckFastElements(scratch, array_length, &bailout);
 
   // If the array has length zero, return the empty string.
   __ ldr(array_length, FieldMemOperand(array, JSArray::kLengthOffset));
   __ SmiUntag(array_length, SetCC);
   __ b(ne, &non_trivial_array);
   __ LoadRoot(r0, Heap::kempty_stringRootIndex);
   __ b(&done);
 
   __ bind(&non_trivial_array);
 
@@ skipping 16 matching lines @@
   //   string_length: Accumulated sum of string lengths (smi).
   //   element: Current array element.
   //   elements_end: Array end.
   if (generate_debug_code_) {
     __ cmp(array_length, Operand::Zero());
     __ Assert(gt, "No empty arrays here in EmitFastAsciiArrayJoin");
   }
   __ bind(&loop);
   __ ldr(string, MemOperand(element, kPointerSize, PostIndex));
   __ JumpIfSmi(string, &bailout);
-  __ ldr(scratch1, FieldMemOperand(string, HeapObject::kMapOffset));
-  __ ldrb(scratch1, FieldMemOperand(scratch1, Map::kInstanceTypeOffset));
-  __ JumpIfInstanceTypeIsNotSequentialAscii(scratch1, scratch2, &bailout);
-  __ ldr(scratch1, FieldMemOperand(string, SeqOneByteString::kLengthOffset));
-  __ add(string_length, string_length, Operand(scratch1), SetCC);
+  __ ldr(scratch, FieldMemOperand(string, HeapObject::kMapOffset));
+  __ ldrb(scratch, FieldMemOperand(scratch, Map::kInstanceTypeOffset));
+  __ JumpIfInstanceTypeIsNotSequentialAscii(scratch, scratch, &bailout);
+  __ ldr(scratch, FieldMemOperand(string, SeqOneByteString::kLengthOffset));
+  __ add(string_length, string_length, Operand(scratch), SetCC);
   __ b(vs, &bailout);
   __ cmp(element, elements_end);
   __ b(lt, &loop);
 
   // If array_length is 1, return elements[0], a string.
   __ cmp(array_length, Operand(1));
   __ b(ne, &not_size_one_array);
   __ ldr(r0, FieldMemOperand(elements, FixedArray::kHeaderSize));
   __ b(&done);
 
   __ bind(&not_size_one_array);
 
   // Live values in registers:
   //   separator: Separator string
   //   array_length: Length of the array.
   //   string_length: Sum of string lengths (smi).
   //   elements: FixedArray of strings.
 
   // Check that the separator is a flat ASCII string.
   __ JumpIfSmi(separator, &bailout);
-  __ ldr(scratch1, FieldMemOperand(separator, HeapObject::kMapOffset));
-  __ ldrb(scratch1, FieldMemOperand(scratch1, Map::kInstanceTypeOffset));
-  __ JumpIfInstanceTypeIsNotSequentialAscii(scratch1, scratch2, &bailout);
+  __ ldr(scratch, FieldMemOperand(separator, HeapObject::kMapOffset));
+  __ ldrb(scratch, FieldMemOperand(scratch, Map::kInstanceTypeOffset));
+  __ JumpIfInstanceTypeIsNotSequentialAscii(scratch, scratch, &bailout);
 
   // Add (separator length times array_length) - separator length to the
   // string_length to get the length of the result string. array_length is not
   // smi but the other values are, so the result is a smi
-  __ ldr(scratch1, FieldMemOperand(separator, SeqOneByteString::kLengthOffset));
-  __ sub(string_length, string_length, Operand(scratch1));
-  __ smull(scratch2, ip, array_length, scratch1);
+  __ ldr(scratch, FieldMemOperand(separator, SeqOneByteString::kLengthOffset));
+  __ sub(string_length, string_length, Operand(scratch));
+  __ smull(scratch, ip, array_length, scratch);
   // Check for smi overflow. No overflow if higher 33 bits of 64-bit result are
   // zero.
   __ cmp(ip, Operand::Zero());
   __ b(ne, &bailout);
-  __ tst(scratch2, Operand(0x80000000));
+  __ tst(scratch, Operand(0x80000000));
   __ b(ne, &bailout);
-  __ add(string_length, string_length, Operand(scratch2), SetCC);
+  __ add(string_length, string_length, Operand(scratch), SetCC);
   __ b(vs, &bailout);
   __ SmiUntag(string_length);
 
   // Get first element in the array to free up the elements register to be used
   // for the result.
   __ add(element,
          elements, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
   result = elements;  // End of live range for elements.
   elements = no_reg;
   // Live values in registers:
   //   element: First array element
   //   separator: Separator string
   //   string_length: Length of result string (not smi)
   //   array_length: Length of the array.
+  __ push(separator);    // Push separator to reuse register as a scratch.

[Rodolph Perfetta, 2013/07/30 15:19:08]

If the comment above is correct then r4 is available and you don't need to push
onto the stack.

[rmcilroy, 2013/07/30 17:12:37]

Nice catch! I spent ages looking for a free reg here, don't know how I missed
r4.

   __ AllocateAsciiString(result,
                          string_length,
-                         scratch1,
-                         scratch2,
+                         scratch,
+                         separator,
                          elements_end,
-                         &bailout);
+                         &pop_and_bailout);
+  __ pop(separator);
   // Prepare for looping. Set up elements_end to end of the array. Set
   // result_pos to the position of the result where to write the first
   // character.
   __ add(elements_end, element, Operand(array_length, LSL, kPointerSizeLog2));
   result_pos = array_length;  // End of live range for array_length.
   array_length = no_reg;
   __ add(result_pos,
          result,
          Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
 
   // Check the length of the separator.
-  __ ldr(scratch1, FieldMemOperand(separator, SeqOneByteString::kLengthOffset));
-  __ cmp(scratch1, Operand(Smi::FromInt(1)));
+  __ ldr(scratch, FieldMemOperand(separator, SeqOneByteString::kLengthOffset));
+  __ cmp(scratch, Operand(Smi::FromInt(1)));
   __ b(eq, &one_char_separator);
   __ b(gt, &long_separator);
 
   // Empty separator case
   __ bind(&empty_separator_loop);
   // Live values in registers:
   //   result_pos: the position to which we are currently copying characters.
   //   element: Current array element.
   //   elements_end: Array end.
 
   // Copy next array element to the result.
   __ ldr(string, MemOperand(element, kPointerSize, PostIndex));
   __ ldr(string_length, FieldMemOperand(string, String::kLengthOffset));
   __ SmiUntag(string_length);
   __ add(string,
          string,
          Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
-  __ CopyBytes(string, result_pos, string_length, scratch1);
+  __ CopyBytes(string, result_pos, string_length, scratch);
   __ cmp(element, elements_end);
   __ b(lt, &empty_separator_loop);  // End while (element < elements_end).
   ASSERT(result.is(r0));
   __ b(&done);
 
   // One-character separator case
   __ bind(&one_char_separator);
   // Replace separator with its ASCII character value.
   __ ldrb(separator, FieldMemOperand(separator, SeqOneByteString::kHeaderSize));
   // Jump into the loop after the code that copies the separator, so the first
@@ skipping 11 matching lines @@
   __ strb(separator, MemOperand(result_pos, 1, PostIndex));
 
   // Copy next array element to the result.
   __ bind(&one_char_separator_loop_entry);
   __ ldr(string, MemOperand(element, kPointerSize, PostIndex));
   __ ldr(string_length, FieldMemOperand(string, String::kLengthOffset));
   __ SmiUntag(string_length);
   __ add(string,
          string,
          Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
-  __ CopyBytes(string, result_pos, string_length, scratch1);
+  __ CopyBytes(string, result_pos, string_length, scratch);
   __ cmp(element, elements_end);
   __ b(lt, &one_char_separator_loop);  // End while (element < elements_end).
   ASSERT(result.is(r0));
   __ b(&done);
 
   // Long separator case (separator is more than one character). Entry is at the
   // label long_separator below.
   __ bind(&long_separator_loop);
   // Live values in registers:
   //   result_pos: the position to which we are currently copying characters.
   //   element: Current array element.
   //   elements_end: Array end.
   //   separator: Separator string.
 
   // Copy the separator to the result.
   __ ldr(string_length, FieldMemOperand(separator, String::kLengthOffset));
   __ SmiUntag(string_length);
   __ add(string,
          separator,
          Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
-  __ CopyBytes(string, result_pos, string_length, scratch1);
+  __ CopyBytes(string, result_pos, string_length, scratch);
 
   __ bind(&long_separator);
   __ ldr(string, MemOperand(element, kPointerSize, PostIndex));
   __ ldr(string_length, FieldMemOperand(string, String::kLengthOffset));
   __ SmiUntag(string_length);
   __ add(string,
          string,
          Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
-  __ CopyBytes(string, result_pos, string_length, scratch1);
+  __ CopyBytes(string, result_pos, string_length, scratch);
   __ cmp(element, elements_end);
   __ b(lt, &long_separator_loop);  // End while (element < elements_end).
   ASSERT(result.is(r0));
   __ b(&done);
 
+  __ bind(&pop_and_bailout);
+  __ Drop(1, al);
   __ bind(&bailout);
   __ LoadRoot(r0, Heap::kUndefinedValueRootIndex);
   __ bind(&done);
   context()->Plug(r0);
 }
 
 
 void FullCodeGenerator::VisitCallRuntime(CallRuntime* expr) {
   Handle<String> name = expr->name();
   if (name->length() > 0 && name->Get(0) == '_') {
@@ skipping 707 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM