Don't memset-zero the BacktrackingAllocator::vregs array of non-trivial VirtualRegister instances

2 files changed, 11 insertions, 15 deletions

diff --git a/js/src/jit/BacktrackingAllocator.cpp b/js/src/jit/BacktrackingAllocator.cpp
index 94ef25785..73aceeccb 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;
diff --git a/js/src/jit/BacktrackingAllocator.h b/js/src/jit/BacktrackingAllocator.h
index 6d14ffacd..9910498fb 100644
--- a/js/src/jit/BacktrackingAllocator.h
+++ b/js/src/jit/BacktrackingAllocator.h
@@ -478,34 +478,31 @@ class LiveBundle : public TempObject
 class VirtualRegister
 {
     // Instruction which defines this register.
-    LNode* ins_;
+    LNode* ins_ = nullptr;
 
     // Definition in the instruction for this register.
-    LDefinition* def_;
+    LDefinition* def_ = nullptr;
 
     // All live ranges for this register. These may overlap each other, and are
     // ordered by their start position.
     InlineForwardList<LiveRange::RegisterLink> ranges_;
 
     // Whether def_ is a temp or an output.
-    bool isTemp_;
+    bool isTemp_ = false;
 
     // Whether this vreg is an input for some phi. This use is not reflected in
     // any range on the vreg.
-    bool usedByPhi_;
+    bool usedByPhi_ = false;
 
     // If this register's definition is MUST_REUSE_INPUT, whether a copy must
     // be introduced before the definition that relaxes the policy.
-    bool mustCopyInput_;
+    bool mustCopyInput_ = false;
 
     void operator=(const VirtualRegister&) = delete;
     VirtualRegister(const VirtualRegister&) = delete;
 
   public:
-    explicit VirtualRegister()
-    {
-        // Note: This class is zeroed before it is constructed.
-    }
+    VirtualRegister() = default;
 
     void init(LNode* ins, LDefinition* def, bool isTemp) {
         MOZ_ASSERT(!ins_);