DMD Issue with Asm Generation?

[user001 via Digitalmars-d]

There seems to be some invalid code generation for std.format for 
type of "real". Relavant links:


https://github.com/D-Programming-Language/phobos/blob/master/std/format.d#L1713
https://github.com/D-Programming-Language/phobos/blob/master/std/math.d#L5118


movabs rbx,7FF0| <-- problem, should 
be 0x7FFF

and rax,rbx|
cmp rax,rbx|
jne test.7FF6FF4762E4  |
mov rdx,qword ptr ss:[rbp-230] |
movabs rcx,F   |
test rdx,rcx   |
je test.7FF6FF4762E4   |
lea rax,qword ptr ds:[7FF6FF4C5C02]| ;7FF6FF4C5C02:"nan"
mov qword ptr ss:[rbp-2C8],rax |
mov qword ptr ss:[rbp-2D0],3   |
jmp test.7FF6FF476335  |
mov rsi,qword ptr ss:[rbp-230] |
movabs rax,7FFF|
and rsi,rax|
cmp rsi,rbx|
jne test.7FF6FF476335  |
fld tword ptr ss:[rbp-228] |
fldz   |
fcompi st1 |
fstp st0   |
ja test.7FF6FF47631B   |
jp test.7FF6FF47631B   |
lea rdx,qword ptr ds:[7FF6FF4C5C06]| ;7FF6FF4C5C06:"inf"
mov ebx,3  |
jmp test.7FF6FF476327  | ;format.d:1495
lea rdx,qword ptr ds:[7FF6FF4C5C0A]| ;7FF6FF4C5C0A:"-inf"

Seems to compile fine with DMD at least with simpler code with 
just an if statement. Also this issue doesn't exist for 32-bit 
x86.

Re: DMD Issue with Asm Generation?

[user001 via Digitalmars-d]

Disregard all that above, looks like someone used a "double" 
which uses 0x7FF0 to check if infinite. Not sure why the code 
runs fine on x86 though, different library maybe?


https://github.com/D-Programming-Language/phobos/blob/master/std/format.d#L1709

Re: DMD Issue with Asm Generation?

[jkpl via Digitalmars-d]

On Saturday, 13 February 2016 at 20:50:22 UTC, user001 wrote:
Disregard all that above, looks like someone used a "double" 
which uses 0x7FF0 to check if infinite. Not sure why the code 
runs fine on x86 though, different library maybe?


https://github.com/D-Programming-Language/phobos/blob/master/std/format.d#L1709


yes the line you highlight is for DMD64 (windows of course), 
which explains well why x86 is OK since it uses the C runtime 
library by DigitalMars (aka snn.lib). Now I'm not quite sure if 
it should be


T tval = val;

because of the comment just after:


convert early to get "inf" in case of overflow