Bug 1025475: SIMD x86-x64: Implement SIMD constructors; r=sunfish
Bug 1025475: SIMD: Introduce SimdConstant; r=sunfish
Bug 1025475: SIMD x86-x64: Implement SIMD constants; r=sunfish
Bug 1025475: SIMD: Fold SIMD created values into SimdConstants; r=sunfish