// dmd -betterC extern(C) void main(int argc, char** argv) { int[4] arr = 1; } Results in: bugs/smallarray.d:(.text.main[main]+0x1f): undefined reference to `_memset32' That is a meager four 32-bit stores. It's an unnecessary pessimization to defer this to a *function call*, source of which may or may not be visible to the compiler, implementation of which would have branches. Compiler should just emit the four stores here. This is not just for ints, other built-in types should also benefit. Upper bound for avoiding the function call may be up to 512 bits worth of stores (to correspond to current SIMD widths).
With the current master, Look Ma, no memset32!! _D4testQfFZv: 0000: 55 push RBP 0001: 48 8B EC mov RBP,RSP 0004: 48 83 EC 10 sub RSP,010h 0008: 48 B8 01 00 00 00 01 00 00 00 mov RAX,0100000001h 0012: 48 89 45 F0 mov -010h[RBP],RAX 0016: 48 89 45 F8 mov -8[RBP],RAX 001a: C9 leave 001b: C3 ret