On Windows, most of Chromium builds with /O1 /Os (optimize for size), but some of it builds with /O2 /Ot (optimize for speed).

For this code:

  void f(int x, int y);
  void g(int x) {
    f(x, 1);
  }

clang -target i686-pc-win32 -Os generates:

00000000 <?g@@YAXH@Z>:
   0:	6a 01                	push   $0x1
   2:	ff 74 24 08          	pushl  0x8(%esp)
   6:	e8 00 00 00 00       	call   b <?g@@YAXH@Z+0xb>
   b:	83 c4 08             	add    $0x8,%esp
   e:	c3                      ret

but with -O2 it generates:

00000000 <?g@@YAXH@Z>:
   0:	83 ec 08             	sub    $0x8,%esp
   3:	8b 44 24 0c          	mov    0xc(%esp),%eax
   7:	89 04 24             	mov    %eax,(%esp)
   a:	c7 44 24 04 01 00 00 	movl   $0x1,0x4(%esp)
  11:	00 
  12:	e8 00 00 00 00       	call   17 <?g@@YAXH@Z+0x17>
  17:	83 c4 08             	add    $0x8,%esp
  1a:	c3                      ret


Is the -O2 version actually faster enough to justify the size increase here?