[Issue 22583] Corrupted function parameters

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22583

hsteoh at qfbox.info changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hsteoh at qfbox.info

--- Comment #3 from hsteoh at qfbox.info ---
Disassembly of _Dmain:

0000000000029a50 <_Dmain>:
   29a50:       55                      push   %rbp
   29a51:       48 89 e5                mov    %rsp,%rbp
   29a54:       48 83 ec 40             sub    $0x40,%rsp
   29a58:       c7 45 f0 00 00 00 00    movl   $0x0,-0x10(%rbp)
   29a5f:       c7 45 f4 00 00 00 00    movl   $0x0,-0xc(%rbp)
   29a66:       c7 45 f8 00 00 80 43    movl   $0x43800000,-0x8(%rbp)
   29a6d:       c7 45 fc 00 00 80 43    movl   $0x43800000,-0x4(%rbp)
   29a74:       0f 10 45 f0             movups -0x10(%rbp),%xmm0
   29a78:       0f 29 45 e0             movaps %xmm0,-0x20(%rbp)
   29a7c:       f2 0f 10 45 e0          movsd  -0x20(%rbp),%xmm0
   29a81:       f2 0f 10 4d e8          movsd  -0x18(%rbp),%xmm1  ;<---- this
looks wrong
   29a86:       31 c0                   xor    %eax,%eax
   29a88:       48 89 e0                mov    %rsp,%rax
   29a8b:       c7 40 10 00 00 00 00    movl   $0x0,0x10(%rax)
   29a92:       c7 40 08 00 00 80 3f    movl   $0x3f800000,0x8(%rax)
   29a99:       c7 00 00 00 80 3f       movl   $0x3f800000,(%rax)
   29a9f:       31 c0                   xor    %eax,%eax
   29aa1:       89 c7                   mov    %eax,%edi
   29aa3:       f3 0f 10 1d 55 a5 05    movss  0x5a555(%rip),%xmm3        #
84000 <_fini+0xc24>
   29aaa:       00 
   29aab:       0f 57 ed                xorps  %xmm5,%xmm5
   29aae:       f3 0f 10 3d 4e a5 05    movss  0x5a54e(%rip),%xmm7        #
84004 <_fini+0xc28>
   29ab5:       00 
   29ab6:       0f 28 d3                movaps %xmm3,%xmm2
   29ab9:       0f 28 e5                movaps %xmm5,%xmm4
   29abc:       0f 28 f7                movaps %xmm7,%xmm6
   29abf:       e8 0c 00 00 00          call   29ad0
<_D4test4drawFPvSQo5RectffffffffffZv>
   29ac4:       31 c0                   xor    %eax,%eax
   29ac6:       48 83 c4 40             add    $0x40,%rsp
   29aca:       5d                      pop    %rbp
   29acb:       c3                      ret
------

Something is fishy with the codegen here.

- The start of the function loads 4 float values (0, 0, 256f (==0x43800000),
256f) onto the stack locations (rbp-10), (rbp-0c), (rbp-8), (rbp-4): this is
the initialization of the temporary Rectf.
- Immediately after that, it loads (rbp-10) into xmm0, copies xmm0 to (rbp-20),
then (rbp-20) back to xmm0.  Not sure what's the point of this, but it seems to
have something to do with data alignment.
- Then it loads (rbp-18) into xmm1: this looks wrong, (rbp-18) has never been
initialized up to this point, so this loads a garbage value into xmm1 (this
line is marked "this looks wrong" in the listing above).  This appears to be
the reason assert(region.y == 0) fails.

Not sure what exactly is going on with the codegen here, but this appears to be
the point where the bug happens.

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