Reviewers: Michael Starzinger,
Description:
ARM microoptimizations to megamorphic stub probing.
Please review this at https://chromiumcodereview.appspot.com/9323002/
SVN Base: http://v8.googlecode.com/svn/branches/bleeding_edge/
Affected files:
M src/arm/stub-cache-arm.cc
M src/objects.h
M src/stub-cache.h
Index: src/arm/stub-cache-arm.cc
===================================================================
--- src/arm/stub-cache-arm.cc (revision 10584)
+++ src/arm/stub-cache-arm.cc (working copy)
@@ -45,6 +45,7 @@
StubCache::Table table,
Register name,
Register offset,
+ int offset_shift_bits,
Register scratch,
Register scratch2) {
ExternalReference
key_offset(isolate->stub_cache()->key_reference(table));
@@ -63,23 +64,26 @@
// Check that the key in the entry matches the name.
__ mov(offsets_base_addr, Operand(key_offset));
- __ ldr(ip, MemOperand(offsets_base_addr, offset, LSL, 1));
+ __ ldr(ip, MemOperand(offsets_base_addr, offset, LSL, 1 +
offset_shift_bits));
__ cmp(name, ip);
__ b(ne, &miss);
// Get the code entry from the cache.
__ add(offsets_base_addr, offsets_base_addr,
Operand(value_off_addr - key_off_addr));
- __ ldr(scratch2, MemOperand(offsets_base_addr, offset, LSL, 1));
+ __ ldr(scratch2,
+ MemOperand(offsets_base_addr, offset, LSL, 1 +
offset_shift_bits));
// Check that the flags match what we're looking for.
__ ldr(scratch2, FieldMemOperand(scratch2, Code::kFlagsOffset));
__ bic(scratch2, scratch2, Operand(Code::kFlagsNotUsedInLookup));
- __ cmp(scratch2, Operand(flags));
+ // Using cmn and the negative instead of cmp means we can use movw.
+ __ cmn(scratch2, Operand(-flags));
__ b(ne, &miss);
// Re-load code entry from cache.
- __ ldr(offset, MemOperand(offsets_base_addr, offset, LSL, 1));
+ __ ldr(offset,
+ MemOperand(offsets_base_addr, offset, LSL, 1 +
offset_shift_bits));
// Jump to the first instruction in the code stub.
__ add(offset, offset, Operand(Code::kHeaderSize - kHeapObjectTag));
@@ -189,23 +193,39 @@
__ ldr(scratch, FieldMemOperand(name, String::kHashFieldOffset));
__ ldr(ip, FieldMemOperand(receiver, HeapObject::kMapOffset));
__ add(scratch, scratch, Operand(ip));
- __ eor(scratch, scratch, Operand(flags));
- __ and_(scratch,
- scratch,
- Operand((kPrimaryTableSize - 1) << kHeapObjectTagSize));
+ uint32_t mask = (kPrimaryTableSize - 1) << kHeapObjectTagSize;
+ // Mask down the eor argument to the minimum to keep the immediate
+ // ARM-encodable.
+ __ eor(scratch, scratch, Operand(flags & mask));
+ // Prefer ubfx to and_ here because the mask is not ARM-encodable.
+ __ Ubfx(scratch, scratch, kHeapObjectTagSize, kPrimaryTableBits);
// Probe the primary table.
- ProbeTable(isolate, masm, flags, kPrimary, name, scratch, extra, extra2);
+ ProbeTable(isolate,
+ masm,
+ flags,
+ kPrimary,
+ name,
+ scratch,
+ kHeapObjectTagSize,
+ extra,
+ extra2);
// Primary miss: Compute hash for secondary probe.
- __ sub(scratch, scratch, Operand(name));
+ __ rsb(scratch, name, Operand(scratch, LSL, kHeapObjectTagSize));
__ add(scratch, scratch, Operand(flags));
- __ and_(scratch,
- scratch,
- Operand((kSecondaryTableSize - 1) << kHeapObjectTagSize));
+ __ Ubfx(scratch, scratch, kHeapObjectTagSize, kSecondaryTableBits);
// Probe the secondary table.
- ProbeTable(isolate, masm, flags, kSecondary, name, scratch, extra,
extra2);
+ ProbeTable(isolate,
+ masm,
+ flags,
+ kSecondary,
+ name,
+ scratch,
+ kHeapObjectTagSize,
+ extra,
+ extra2);
// Cache miss: Fall-through and let caller handle the miss by
// entering the runtime system.
Index: src/objects.h
===================================================================
--- src/objects.h (revision 10584)
+++ src/objects.h (working copy)
@@ -4364,8 +4364,8 @@
// Flags layout. BitField<type, shift, size>.
class ICStateField: public BitField<InlineCacheState, 0, 3> {};
class TypeField: public BitField<PropertyType, 3, 4> {};
- class KindField: public BitField<Kind, 7, 4> {};
- class CacheHolderField: public BitField<InlineCacheHolderFlag, 11, 1> {};
+ class CacheHolderField: public BitField<InlineCacheHolderFlag, 7, 1> {};
+ class KindField: public BitField<Kind, 8, 4> {};
class ExtraICStateField: public BitField<ExtraICState, 12, 2> {};
class IsPregeneratedField: public BitField<bool, 14, 1> {};
@@ -4373,6 +4373,7 @@
static const int kArgumentsCountShift = 15;
static const int kArgumentsCountMask = ~((1 << kArgumentsCountShift) -
1);
+ // This constant should be encodable in an ARM instruction.
static const int kFlagsNotUsedInLookup =
TypeField::kMask | CacheHolderField::kMask;
Index: src/stub-cache.h
===================================================================
--- src/stub-cache.h (revision 10584)
+++ src/stub-cache.h (working copy)
@@ -343,8 +343,10 @@
reinterpret_cast<Address>(table) + (offset << shift_amount));
}
- static const int kPrimaryTableSize = 2048;
- static const int kSecondaryTableSize = 512;
+ static const int kPrimaryTableBits = 11;
+ static const int kPrimaryTableSize = (1 << kPrimaryTableBits);
+ static const int kSecondaryTableBits = 9;
+ static const int kSecondaryTableSize = (1 << kSecondaryTableBits);
Entry primary_[kPrimaryTableSize];
Entry secondary_[kSecondaryTableSize];
--
v8-dev mailing list
[email protected]
http://groups.google.com/group/v8-dev
