1 files changed, 28 insertions, 16 deletions

diff --git a/js/src/jit/BacktrackingAllocator.cpp b/js/src/jit/BacktrackingAllocator.cpp
index 94ef25785..645aefc4f 100644
--- a/js/src/jit/BacktrackingAllocator.cpp
+++ b/js/src/jit/BacktrackingAllocator.cpp
@@ -378,7 +378,6 @@ BacktrackingAllocator::init()
     size_t numVregs = graph.numVirtualRegisters();
     if (!vregs.init(mir->alloc(), numVregs))
         return false;
-    memset(&vregs[0], 0, sizeof(VirtualRegister) * numVregs);
     for (uint32_t i = 0; i < numVregs; i++)
         new(&vregs[i]) VirtualRegister();
 
@@ -1101,9 +1100,9 @@ BacktrackingAllocator::mergeAndQueueRegisters()
             if (iter->isParameter()) {
                 for (size_t i = 0; i < iter->numDefs(); i++) {
                     DebugOnly<bool> found = false;
-                    VirtualRegister &paramVreg = vreg(iter->getDef(i));
+                    VirtualRegister& paramVreg = vreg(iter->getDef(i));
                     for (; original < paramVreg.vreg(); original++) {
-                        VirtualRegister &originalVreg = vregs[original];
+                        VirtualRegister& originalVreg = vregs[original];
                         if (*originalVreg.def()->output() == *iter->getDef(i)->output()) {
                             MOZ_ASSERT(originalVreg.ins()->isParameter());
                             if (!tryMergeBundles(originalVreg.firstBundle(), paramVreg.firstBundle()))
@@ -1136,7 +1135,7 @@ BacktrackingAllocator::mergeAndQueueRegisters()
         LBlock* block = graph.getBlock(i);
         for (size_t j = 0; j < block->numPhis(); j++) {
             LPhi* phi = block->getPhi(j);
-            VirtualRegister &outputVreg = vreg(phi->getDef(0));
+            VirtualRegister& outputVreg = vreg(phi->getDef(0));
             for (size_t k = 0, kend = phi->numOperands(); k < kend; k++) {
                 VirtualRegister& inputVreg = vreg(phi->getOperand(k)->toUse());
                 if (!tryMergeBundles(inputVreg.firstBundle(), outputVreg.firstBundle()))
@@ -1334,7 +1333,7 @@ BacktrackingAllocator::computeRequirement(LiveBundle* bundle,
 
     for (LiveRange::BundleLinkIterator iter = bundle->rangesBegin(); iter; iter++) {
         LiveRange* range = LiveRange::get(*iter);
-        VirtualRegister &reg = vregs[range->vreg()];
+        VirtualRegister& reg = vregs[range->vreg()];
 
         if (range->hasDefinition()) {
             // Deal with any definition constraints/hints.
@@ -1396,7 +1395,7 @@ BacktrackingAllocator::tryAllocateRegister(PhysicalRegister& r, LiveBundle* bund
 
     for (LiveRange::BundleLinkIterator iter = bundle->rangesBegin(); iter; iter++) {
         LiveRange* range = LiveRange::get(*iter);
-        VirtualRegister &reg = vregs[range->vreg()];
+        VirtualRegister& reg = vregs[range->vreg()];
 
         if (!reg.isCompatible(r.reg))
             return true;
@@ -1737,6 +1736,18 @@ BacktrackingAllocator::deadRange(LiveRange* range)
 }
 
 bool
+BacktrackingAllocator::moveAtEdge(LBlock* predecessor, LBlock* successor, LiveRange* from,
+                                  LiveRange* to, LDefinition::Type type)
+{
+    if (successor->mir()->numPredecessors() > 1) {
+        MOZ_ASSERT(predecessor->mir()->numSuccessors() == 1);
+        return moveAtExit(predecessor, from, to, type);
+    }
+
+    return moveAtEntry(successor, from, to, type);
+}
+
+bool
 BacktrackingAllocator::resolveControlFlow()
 {
     // Add moves to handle changing assignments for vregs over their lifetime.
@@ -1844,10 +1855,15 @@ BacktrackingAllocator::resolveControlFlow()
                 LiveRange* from = vreg(input).rangeFor(exitOf(predecessor), /* preferRegister = */ true);
                 MOZ_ASSERT(from);
 
-                if (!alloc().ensureBallast())
+                if (!alloc().ensureBallast()) {
                     return false;
-                if (!moveAtExit(predecessor, from, to, def->type()))
+                }
+
+                // Note: we have to use moveAtEdge both here and below (for edge
+                // resolution) to avoid conflicting moves. See bug 1493900.
+                if (!moveAtEdge(predecessor, successor, from, to, def->type())) {
                     return false;
+                }
             }
         }
     }
@@ -1876,16 +1892,12 @@ BacktrackingAllocator::resolveControlFlow()
                     if (targetRange->covers(exitOf(predecessor)))
                         continue;
 
-                    if (!alloc().ensureBallast())
+                    if (!alloc().ensureBallast()) {
                         return false;
+                    }
                     LiveRange* from = reg.rangeFor(exitOf(predecessor), true);
-                    if (successor->mir()->numPredecessors() > 1) {
-                        MOZ_ASSERT(predecessor->mir()->numSuccessors() == 1);
-                        if (!moveAtExit(predecessor, from, targetRange, reg.type()))
-                            return false;
-                    } else {
-                        if (!moveAtEntry(successor, from, targetRange, reg.type()))
-                            return false;
+                    if (!moveAtEdge(predecessor, successor, from, targetRange, reg.type())) {
+                        return false;
                     }
                 }
             }