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Use immediate add when possible in space allocator

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Save one instruction in allocating new space by using an immediate add if
possible to calculate the new top of heap.

BUG=

Review URL: https://chromiumcodereview.appspot.com/11091068
Patch from Anthony Berent <aberent@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12718 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
danno@chromium.org 2012-10-12 14:06:03 +00:00
parent c969afe137
commit bf83c5fe32
1 changed files with 12 additions and 2 deletions
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14
src/arm/macro-assembler-arm.cc
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@ -1570,7 +1570,11 @@ void MacroAssembler::AllocateInNewSpace(int object_size,
Register topaddr = scratch1;
Register obj_size_reg = scratch2;
mov(topaddr, Operand(new_space_allocation_top));
mov(obj_size_reg, Operand(object_size));
Operand obj_size_operand = Operand(object_size);
if (!obj_size_operand.is_single_instruction(this)) {
// We are about to steal IP, so we need to load this value first
mov(obj_size_reg, obj_size_operand);
}
// This code stores a temporary value in ip. This is OK, as the code below
// does not need ip for implicit literal generation.
@ -1592,7 +1596,13 @@ void MacroAssembler::AllocateInNewSpace(int object_size,
// Calculate new top and bail out if new space is exhausted. Use result
// to calculate the new top.
add(scratch2, result, Operand(obj_size_reg), SetCC);
if (obj_size_operand.is_single_instruction(this)) {
// We can add the size as an immediate
add(scratch2, result, obj_size_operand, SetCC);
} else {
// Doesn't fit in an immediate, we have to use the register
add(scratch2, result, obj_size_reg, SetCC);
}
b(cs, gc_required);
cmp(scratch2, Operand(ip));
b(hi, gc_required);