Bug 1264948 - MBasicBlock::addPredecessor, check for OOMs when allocating Phi nodes. r=h4writer

js/src/jit/MIR.h

@@ -7548,6 +7548,9 @@ class MPhi final
     static MPhi* New(TempAllocator& alloc, MIRType resultType = MIRType::Value) {
         return new(alloc) MPhi(alloc, resultType);
     }
+    static MPhi* New(TempAllocator::Fallible alloc, MIRType resultType = MIRType::Value) {
+        return new(alloc) MPhi(alloc.alloc, resultType);
+    }
 
     void removeOperand(size_t index);
     void removeAllOperands();

js/src/jit/MIRGraph.cpp

@@ -1193,9 +1193,11 @@ MBasicBlock::addPredecessorPopN(TempAllocator& alloc, MBasicBlock* pred, uint32_
                 // Otherwise, create a new phi node.
                 MPhi* phi;
                 if (mine->type() == other->type())
-                    phi = MPhi::New(alloc, mine->type());
+                    phi = MPhi::New(alloc.fallible(), mine->type());
                 else
-                    phi = MPhi::New(alloc);
+                    phi = MPhi::New(alloc.fallible());
+                if (!phi)
+                    return false;
                 addPhi(phi);
 
                 // Prime the phi for each predecessor, so input(x) comes from