[Bug target/44532] x86-64 unnecessary parameter extension

[steven at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44532

Steven Bosscher  changed:

   What|Removed |Added

 Status|NEW |RESOLVED
   Last reconfirmed|2010-06-14 11:30:39 |2019-3-4
 CC||steven at gcc dot gnu.org
 Resolution|--- |WONTFIX

--- Comment #4 from Steven Bosscher  ---
GCC trunk today:"

f1(short, int):
movswl  %di, %eax
imull   %esi, %eax
ret
f2(unsigned short, int):
movzwl  %di, %eax
imull   %esi, %eax
ret


clang trunk:
f1(short, int):# @f1(short, int)
movl%edi, %eax
imull   %esi, %eax
retq
f2(unsigned short, int):# @f2(unsigned short,
int)
movl%edi, %eax
imull   %esi, %eax
retq


icc 19.0.1:
f1(short, int):
movswq%di, %rax #3.12
imull %esi, %eax#3.16
ret #3.16
f2(unsigned short, int):
movzwl%di, %eax #7.1
imull %esi, %eax#8.16
ret  


Given the comments from H.J. and the icc output, let's WONTFIX this one.

[Bug target/44532] x86-64 unnecessary parameter extension

[jakub at gcc dot gnu dot org]

--- Comment #1 from jakub at gcc dot gnu dot org  2010-06-14 08:01 ---
  tempreg = convert_to_mode (data-nominal_mode, tempreg, unsignedp);

  if (GET_CODE (tempreg) == SUBREG
   GET_MODE (tempreg) == data-nominal_mode
   REG_P (SUBREG_REG (tempreg))
   data-nominal_mode == data-passed_mode
   GET_MODE (SUBREG_REG (tempreg)) == GET_MODE (data-entry_parm)
   GET_MODE_SIZE (GET_MODE (tempreg))
  GET_MODE_SIZE (GET_MODE (data-entry_parm)))
{
  /* The argument is already sign/zero extended, so note it
 into the subreg.  */
  SUBREG_PROMOTED_VAR_P (tempreg) = 1;
  SUBREG_PROMOTED_UNSIGNED_SET (tempreg, unsignedp);
}

For x86_64 and short/char, all the conditions above are true except that
nominal_mode (HImode) != passed_mode (SImode).


-- 

jakub at gcc dot gnu dot org changed:

   What|Removed |Added

 CC||hubicka at gcc dot gnu dot
   ||org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44532

[Bug target/44532] x86-64 unnecessary parameter extension

[rguenth at gcc dot gnu dot org]

--- Comment #2 from rguenth at gcc dot gnu dot org  2010-06-14 11:30 ---
Confirmed.


-- 

rguenth at gcc dot gnu dot org changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
 Ever Confirmed|0   |1
 GCC target triplet||x86-64-*-*, i?86-*-*
   Keywords||missed-optimization
   Last reconfirmed|-00-00 00:00:00 |2010-06-14 11:30:39
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44532

[Bug target/44532] x86-64 unnecessary parameter extension

[hjl dot tools at gmail dot com]

--- Comment #3 from hjl dot tools at gmail dot com  2010-06-15 00:57 ---
We should consider:

1. The x86-64 psABI doesn't say how char/short should be extended
as function parameters.
2. Gcc may not touch upper bits, PR 42324.
3. Gcc never depends on the upper bits which are properly extended
in function parameters.
4. Icc may not touch the upper bits in function parameters on stack.
5. For a function without proper prototype, caller may not properly
extend function parameters.

I think the current way is safer.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44532