From: erik.corry@gmail.com Date: Mon, 6 Dec 2010 09:59:08 +0000 (+0000) Subject: Improve code generated for AllocInNewSpace. This is a commit of http://codereview... X-Git-Tag: upstream/4.7.83~20883 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=bca83462d892c25dbf1e48f183c2170a707c317a;p=platform%2Fupstream%2Fv8.git Improve code generated for AllocInNewSpace. This is a commit of codereview.chromium.org/5512004 for Rodolph Perfetta. git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5917 ce2b1a6d-e550-0410-aec6-3dcde31c8c00 --- diff --git a/src/arm/macro-assembler-arm.cc b/src/arm/macro-assembler-arm.cc index ea85c79..afd7e2c 100644 --- a/src/arm/macro-assembler-arm.cc +++ b/src/arm/macro-assembler-arm.cc @@ -920,6 +920,7 @@ void MacroAssembler::AllocateInNewSpace(int object_size, } ASSERT(!result.is(scratch1)); + ASSERT(!result.is(scratch2)); ASSERT(!scratch1.is(scratch2)); // Make object size into bytes. @@ -928,38 +929,55 @@ void MacroAssembler::AllocateInNewSpace(int object_size, } ASSERT_EQ(0, object_size & kObjectAlignmentMask); - // Load address of new object into result and allocation top address into - // scratch1. + // Check relative positions of allocation top and limit addresses. + // The values must be adjacent in memory to allow the use of LDM. + // Also, assert that the registers are numbered such that the values + // are loaded in the correct order. ExternalReference new_space_allocation_top = ExternalReference::new_space_allocation_top_address(); - mov(scratch1, Operand(new_space_allocation_top)); + ExternalReference new_space_allocation_limit = + ExternalReference::new_space_allocation_limit_address(); + intptr_t top = + reinterpret_cast(new_space_allocation_top.address()); + intptr_t limit = + reinterpret_cast(new_space_allocation_limit.address()); + ASSERT((limit - top) == kPointerSize); + ASSERT(result.code() < ip.code()); + + // Set up allocation top address and object size registers. + Register topaddr = scratch1; + Register obj_size_reg = scratch2; + mov(topaddr, Operand(new_space_allocation_top)); + mov(obj_size_reg, Operand(object_size)); + + // This code stores a temporary value in ip. This is OK, as the code below + // does not need ip for implicit literal generation. if ((flags & RESULT_CONTAINS_TOP) == 0) { - ldr(result, MemOperand(scratch1)); - } else if (FLAG_debug_code) { - // Assert that result actually contains top on entry. scratch2 is used - // immediately below so this use of scratch2 does not cause difference with - // respect to register content between debug and release mode. - ldr(scratch2, MemOperand(scratch1)); - cmp(result, scratch2); - Check(eq, "Unexpected allocation top"); + // Load allocation top into result and allocation limit into ip. + ldm(ia, topaddr, result.bit() | ip.bit()); + } else { + if (FLAG_debug_code) { + // Assert that result actually contains top on entry. ip is used + // immediately below so this use of ip does not cause difference with + // respect to register content between debug and release mode. + ldr(ip, MemOperand(topaddr)); + cmp(result, ip); + Check(eq, "Unexpected allocation top"); + } + // Load allocation limit into ip. Result already contains allocation top. + ldr(ip, MemOperand(topaddr, limit - top)); } // Calculate new top and bail out if new space is exhausted. Use result // to calculate the new top. - ExternalReference new_space_allocation_limit = - ExternalReference::new_space_allocation_limit_address(); - mov(scratch2, Operand(new_space_allocation_limit)); - ldr(scratch2, MemOperand(scratch2)); - add(result, result, Operand(object_size)); - cmp(result, Operand(scratch2)); + add(scratch2, result, Operand(obj_size_reg)); + cmp(scratch2, Operand(ip)); b(hi, gc_required); - str(result, MemOperand(scratch1)); + str(scratch2, MemOperand(topaddr)); - // Tag and adjust back to start of new object. + // Tag object if requested. if ((flags & TAG_OBJECT) != 0) { - sub(result, result, Operand(object_size - kHeapObjectTag)); - } else { - sub(result, result, Operand(object_size)); + add(result, result, Operand(kHeapObjectTag)); } } @@ -982,52 +1000,63 @@ void MacroAssembler::AllocateInNewSpace(Register object_size, } ASSERT(!result.is(scratch1)); + ASSERT(!result.is(scratch2)); ASSERT(!scratch1.is(scratch2)); - // Load address of new object into result and allocation top address into - // scratch1. + // Check relative positions of allocation top and limit addresses. + // The values must be adjacent in memory to allow the use of LDM. + // Also, assert that the registers are numbered such that the values + // are loaded in the correct order. ExternalReference new_space_allocation_top = ExternalReference::new_space_allocation_top_address(); - mov(scratch1, Operand(new_space_allocation_top)); + ExternalReference new_space_allocation_limit = + ExternalReference::new_space_allocation_limit_address(); + intptr_t top = + reinterpret_cast(new_space_allocation_top.address()); + intptr_t limit = + reinterpret_cast(new_space_allocation_limit.address()); + ASSERT((limit - top) == kPointerSize); + ASSERT(result.code() < ip.code()); + + // Set up allocation top address. + Register topaddr = scratch1; + mov(topaddr, Operand(new_space_allocation_top)); + + // This code stores a temporary value in ip. This is OK, as the code below + // does not need ip for implicit literal generation. if ((flags & RESULT_CONTAINS_TOP) == 0) { - ldr(result, MemOperand(scratch1)); - } else if (FLAG_debug_code) { - // Assert that result actually contains top on entry. scratch2 is used - // immediately below so this use of scratch2 does not cause difference with - // respect to register content between debug and release mode. - ldr(scratch2, MemOperand(scratch1)); - cmp(result, scratch2); - Check(eq, "Unexpected allocation top"); + // Load allocation top into result and allocation limit into ip. + ldm(ia, topaddr, result.bit() | ip.bit()); + } else { + if (FLAG_debug_code) { + // Assert that result actually contains top on entry. ip is used + // immediately below so this use of ip does not cause difference with + // respect to register content between debug and release mode. + ldr(ip, MemOperand(topaddr)); + cmp(result, ip); + Check(eq, "Unexpected allocation top"); + } + // Load allocation limit into ip. Result already contains allocation top. + ldr(ip, MemOperand(topaddr, limit - top)); } // Calculate new top and bail out if new space is exhausted. Use result - // to calculate the new top. Object size is in words so a shift is required to - // get the number of bytes - ExternalReference new_space_allocation_limit = - ExternalReference::new_space_allocation_limit_address(); - mov(scratch2, Operand(new_space_allocation_limit)); - ldr(scratch2, MemOperand(scratch2)); + // to calculate the new top. Object size may be in words so a shift is + // required to get the number of bytes. if ((flags & SIZE_IN_WORDS) != 0) { - add(result, result, Operand(object_size, LSL, kPointerSizeLog2)); + add(scratch2, result, Operand(object_size, LSL, kPointerSizeLog2)); } else { - add(result, result, Operand(object_size)); + add(scratch2, result, Operand(object_size)); } - cmp(result, Operand(scratch2)); + cmp(scratch2, Operand(ip)); b(hi, gc_required); // Update allocation top. result temporarily holds the new top. if (FLAG_debug_code) { - tst(result, Operand(kObjectAlignmentMask)); + tst(scratch2, Operand(kObjectAlignmentMask)); Check(eq, "Unaligned allocation in new space"); } - str(result, MemOperand(scratch1)); - - // Adjust back to start of new object. - if ((flags & SIZE_IN_WORDS) != 0) { - sub(result, result, Operand(object_size, LSL, kPointerSizeLog2)); - } else { - sub(result, result, Operand(object_size)); - } + str(scratch2, MemOperand(topaddr)); // Tag object if requested. if ((flags & TAG_OBJECT) != 0) {