Title: [134182] trunk/Source/_javascript_Core
- Revision
- 134182
- Author
- [email protected]
- Date
- 2012-11-11 18:08:06 -0800 (Sun, 11 Nov 2012)
Log Message
DFG register allocation should be greedy rather than round-robin
https://bugs.webkit.org/show_bug.cgi?id=101870
Reviewed by Geoffrey Garen.
This simplifies the code, reduces some code duplication, and shows some slight
performance improvements in a few places, likely due to the fact that lower-numered
registers also typically have smaller encodings.
* dfg/DFGRegisterBank.h:
(JSC::DFG::RegisterBank::RegisterBank):
(JSC::DFG::RegisterBank::tryAllocate):
(JSC::DFG::RegisterBank::allocate):
(JSC::DFG::RegisterBank::allocateInternal):
(RegisterBank):
Modified Paths
Diff
Modified: trunk/Source/_javascript_Core/ChangeLog (134181 => 134182)
--- trunk/Source/_javascript_Core/ChangeLog 2012-11-12 01:41:50 UTC (rev 134181)
+++ trunk/Source/_javascript_Core/ChangeLog 2012-11-12 02:08:06 UTC (rev 134182)
@@ -1,3 +1,21 @@
+2012-11-11 Filip Pizlo <[email protected]>
+
+ DFG register allocation should be greedy rather than round-robin
+ https://bugs.webkit.org/show_bug.cgi?id=101870
+
+ Reviewed by Geoffrey Garen.
+
+ This simplifies the code, reduces some code duplication, and shows some slight
+ performance improvements in a few places, likely due to the fact that lower-numered
+ registers also typically have smaller encodings.
+
+ * dfg/DFGRegisterBank.h:
+ (JSC::DFG::RegisterBank::RegisterBank):
+ (JSC::DFG::RegisterBank::tryAllocate):
+ (JSC::DFG::RegisterBank::allocate):
+ (JSC::DFG::RegisterBank::allocateInternal):
+ (RegisterBank):
+
2012-11-11 Kenichi Ishibashi <[email protected]>
WTFString::utf8() should have a mode of conversion to use replacement character
Modified: trunk/Source/_javascript_Core/dfg/DFGRegisterBank.h (134181 => 134182)
--- trunk/Source/_javascript_Core/dfg/DFGRegisterBank.h 2012-11-12 01:41:50 UTC (rev 134181)
+++ trunk/Source/_javascript_Core/dfg/DFGRegisterBank.h 2012-11-12 02:08:06 UTC (rev 134182)
@@ -75,7 +75,6 @@
public:
RegisterBank()
- : m_lastAllocated(NUM_REGS - 1)
{
}
@@ -86,15 +85,10 @@
{
VirtualRegister ignored;
- for (uint32_t i = m_lastAllocated + 1; i < NUM_REGS; ++i) {
+ for (uint32_t i = 0; i < NUM_REGS; ++i) {
if (!m_data[i].lockCount && m_data[i].name == InvalidVirtualRegister)
return allocateInternal(i, ignored);
}
- // Loop over the remaining entries.
- for (uint32_t i = 0; i <= m_lastAllocated; ++i) {
- if (!m_data[i].lockCount && m_data[i].name == InvalidVirtualRegister)
- return allocateInternal(i, ignored);
- }
return (RegID)-1;
}
@@ -115,9 +109,6 @@
uint32_t currentLowest = NUM_REGS;
SpillHint currentSpillOrder = SpillHintInvalid;
- // Scan through all register, starting at the last allocated & looping around.
- ASSERT(m_lastAllocated < NUM_REGS);
-
// This loop is broken into two halves, looping from the last allocated
// register (the register returned last time this method was called) to
// the maximum register value, then from 0 to the last allocated.
@@ -125,7 +116,7 @@
// thrash, and minimize time spent scanning locked registers in allocation.
// If a unlocked and unnamed register is found return it immediately.
// Otherwise, find the first unlocked register with the lowest spillOrder.
- for (uint32_t i = m_lastAllocated + 1; i < NUM_REGS; ++i) {
+ for (uint32_t i = 0 ; i < NUM_REGS; ++i) {
// (1) If the current register is locked, it is not a candidate.
if (m_data[i].lockCount)
continue;
@@ -140,18 +131,6 @@
currentLowest = i;
}
}
- // Loop over the remaining entries.
- for (uint32_t i = 0; i <= m_lastAllocated; ++i) {
- if (m_data[i].lockCount)
- continue;
- SpillHint spillOrder = m_data[i].spillOrder;
- if (spillOrder == SpillHintInvalid)
- return allocateInternal(i, spillMe);
- if (spillOrder < currentSpillOrder) {
- currentSpillOrder = spillOrder;
- currentLowest = i;
- }
- }
// Deadlock check - this could only occur is all registers are locked!
ASSERT(currentLowest != NUM_REGS && currentSpillOrder != SpillHintInvalid);
@@ -354,7 +333,6 @@
// Mark the register as locked (with a lock count of 1).
m_data[i].lockCount = 1;
- m_lastAllocated = i;
return BankInfo::toRegister(i);
}
@@ -378,8 +356,6 @@
// Holds the current status of all registers.
MapEntry m_data[NUM_REGS];
- // Used to to implement a simple round-robin like allocation scheme.
- uint32_t m_lastAllocated;
};
} } // namespace JSC::DFG
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