[turbofan] mark Float64(Max|Min) as associative and commutative.

Now that -0.0 and 0.0 are ordered by Float64Max and Float64Min, these
two operator are both associative and commutative for all numbers. The
operators would not be associative and commutative for NaNs, but
neither JavaScript nor WebAssembly distinguish between NaNs nowadays.

R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2263163002
Cr-Commit-Position: refs/heads/master@{#38791}

src/compiler/machine-operator.cc

@@ -183,8 +183,8 @@ MachineRepresentation AtomicStoreRepresentationOf(Operator const* op) {
   V(Float64Log1p, Operator::kNoProperties, 1, 0, 1)                          \
   V(Float64Log2, Operator::kNoProperties, 1, 0, 1)                           \
   V(Float64Log10, Operator::kNoProperties, 1, 0, 1)                          \
-  V(Float64Max, Operator::kNoProperties, 2, 0, 1)                            \
-  V(Float64Min, Operator::kNoProperties, 2, 0, 1)                            \
+  V(Float64Max, Operator::kAssociative | Operator::kCommutative, 2, 0, 1)    \
+  V(Float64Min, Operator::kAssociative | Operator::kCommutative, 2, 0, 1)    \
   V(Float64Neg, Operator::kNoProperties, 1, 0, 1)                            \
   V(Float64Add, Operator::kCommutative, 2, 0, 1)                             \
   V(Float64Sub, Operator::kNoProperties, 2, 0, 1)                            \