http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59405
Bug ID: 59405
Summary: Incorrect FP<->MMX transition during call/ret
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: kirill.yukhin at intel dot com
Hello,
Attached test reproduces the error:
$ gcc -m32 -mmmx 1.c
$ ./a.out
Aborted (core dumped)
Disassembly of the foo is:
foo32x2_be:
.LFB0:
pushl %ebp # 22 *pushsi2 [length = 1]
movl %esp, %ebp # 23 *movsi_internal/1 [length = 2]
subl $16, %esp # 24 pro_epilogue_adjust_stack_si_add/1
[length = 3]
movq %mm0, -8(%ebp) # 3 *movv2sf_internal/9 [length = 4]
movl -4(%ebp), %eax # 7 *movsf_internal/4 [length = 3]
movl %eax, -12(%ebp) # 14 *movsf_internal/5 [length = 3]
flds -12(%ebp) # 21 *movsf_internal/1 [length = 3]
leave # 27 leave [length = 1]
ret # 28 simple_return_internal [length = 1]
We're passing v2sf vector using MMX register, which aliased to x87 stack.
Then we're trying to load FP to it, which leds to NaN.
As far as I understand, we need `emms' instruction between last MMX use and
before first x87 use.
Reproduces everywhere, up to 4.7.2 (may be earlier, I have no such).
