Micro-optimize a hot spot in LinearScan; this partially addresses Bug 741317. r=jandem

js/src/ion/LIR.h

@@ -164,6 +164,9 @@ class LAllocation : public TempObject
     bool isRegister() const {
         return isGeneralReg() || isFloatReg();
     }
+    bool isRegister(bool needFloat) const {
+        return needFloat ? isFloatReg() : isGeneralReg();
+    }
     bool isMemory() const {
         return isStackSlot() || isArgument();
     }

js/src/ion/LinearScan.cpp

@@ -906,21 +906,22 @@ LinearScanAllocator::findBestFreeRegister(CodePosition *freeUntil)
     // Compute free-until positions for all registers
     CodePosition freeUntilPos[AnyRegister::Total];
     bool needFloat = vregs[current->vreg()].isDouble();
-    for (AnyRegisterIterator regs(allRegisters_); regs.more(); regs++) {
-        AnyRegister reg = *regs;
-        if (reg.isFloat() == needFloat)
-            freeUntilPos[reg.code()] = CodePosition::MAX;
+    for (RegisterSet regs(allRegisters_); !regs.empty(needFloat); ) {
+        AnyRegister reg = regs.takeAny(needFloat);
+        freeUntilPos[reg.code()] = CodePosition::MAX;
     }
     for (IntervalIterator i(active.begin()); i != active.end(); i++) {
-        if (i->getAllocation()->isRegister()) {
-            AnyRegister reg = i->getAllocation()->toRegister();
+        LAllocation *alloc = i->getAllocation();
+        if (alloc->isRegister(needFloat)) {
+            AnyRegister reg = alloc->toRegister();
             IonSpew(IonSpew_RegAlloc, "   Register %s not free", reg.name());
             freeUntilPos[reg.code()] = CodePosition::MIN;
         }
     }
     for (IntervalIterator i(inactive.begin()); i != inactive.end(); i++) {
-        if (i->getAllocation()->isRegister()) {
-            AnyRegister reg = i->getAllocation()->toRegister();
+        LAllocation *alloc = i->getAllocation();
+        if (alloc->isRegister(needFloat)) {
+            AnyRegister reg = alloc->toRegister();
             CodePosition pos = current->intersect(*i);
             if (pos != CodePosition::MIN && pos < freeUntilPos[reg.code()]) {
                 freeUntilPos[reg.code()] = pos;
@@ -948,8 +949,9 @@ LinearScanAllocator::findBestFreeRegister(CodePosition *freeUntil)
         // As an optimization, use the allocation from the previous interval if
         // it is available.
         LiveInterval *previous = vregs[current->vreg()].getInterval(current->index() - 1);
-        if (previous->getAllocation()->isRegister()) {
-            AnyRegister prevReg = previous->getAllocation()->toRegister();
+        LAllocation *alloc = previous->getAllocation();
+        if (alloc->isRegister(needFloat)) {
+            AnyRegister prevReg = alloc->toRegister();
             if (freeUntilPos[prevReg.code()] != CodePosition::MIN)
                 bestCode = prevReg.code();
         }
@@ -999,14 +1001,14 @@ LinearScanAllocator::findBestBlockedRegister(CodePosition *nextUsed)
     // Compute next-used positions for all registers
     CodePosition nextUsePos[AnyRegister::Total];
     bool needFloat = vregs[current->vreg()].isDouble();
-    for (AnyRegisterIterator regs(allRegisters_); regs.more(); regs++) {
-        AnyRegister reg = *regs;
-        if (reg.isFloat() == needFloat)
-            nextUsePos[reg.code()] = CodePosition::MAX;
+    for (RegisterSet regs(allRegisters_); !regs.empty(needFloat); ) {
+        AnyRegister reg = regs.takeAny(needFloat);
+        nextUsePos[reg.code()] = CodePosition::MAX;
     }
     for (IntervalIterator i(active.begin()); i != active.end(); i++) {
-        if (i->getAllocation()->isRegister()) {
-            AnyRegister reg = i->getAllocation()->toRegister();
+        LAllocation *alloc = i->getAllocation();
+        if (alloc->isRegister(needFloat)) {
+            AnyRegister reg = alloc->toRegister();
             if (i->start().ins() == current->start().ins()) {
                 nextUsePos[reg.code()] = CodePosition::MIN;
                 IonSpew(IonSpew_RegAlloc, "   Disqualifying %s due to recency", reg.name());
@@ -1018,8 +1020,9 @@ LinearScanAllocator::findBestBlockedRegister(CodePosition *nextUsed)
         }
     }
     for (IntervalIterator i(inactive.begin()); i != inactive.end(); i++) {
-        if (i->getAllocation()->isRegister()) {
-            AnyRegister reg = i->getAllocation()->toRegister();
+        LAllocation *alloc = i->getAllocation();
+        if (alloc->isRegister(needFloat)) {
+            AnyRegister reg = alloc->toRegister();
             CodePosition pos = i->nextUsePosAfter(current->start());
             if (pos < nextUsePos[reg.code()]) {
                 nextUsePos[reg.code()] = pos;