On 03/29/2012 03:05 AM, Stephan Bergmann wrote:
> Hi all,
>
> In LibreOffice's ever-beloved low-level code to synthesize calls to
> C++ virtual functions, I'm having the following problem (on Linux
> x86_64). The function callVirtualMethod at
> <http://cgit.freedesktop.org/libreoffice/core/tree/bridges/source/cpp_uno/gcc3_linux_x86-64/uno2cpp.cxx?id=571876c1234ae55aab0198c7e2caf9049fcd230e#n61>
> effectively does the following:
Quoting:
asm volatile (
// Fill the xmm registers
"movq %6, %%rax\n\t"
"movsd (%%rax), %%xmm0\n\t"
"movsd 8(%%rax), %%xmm1\n\t"
"movsd 16(%%rax), %%xmm2\n\t"
"movsd 24(%%rax), %%xmm3\n\t"
"movsd 32(%%rax), %%xmm4\n\t"
"movsd 40(%%rax), %%xmm5\n\t"
"movsd 48(%%rax), %%xmm6\n\t"
"movsd 56(%%rax), %%xmm7\n\t"
// Fill the general purpose registers
"movq %5, %%rax\n\t"
"movq (%%rax), %%rdi\n\t"
"movq 8(%%rax), %%rsi\n\t"
"movq 16(%%rax), %%rdx\n\t"
"movq 24(%%rax), %%rcx\n\t"
"movq 32(%%rax), %%r8\n\t"
"movq 40(%%rax), %%r9\n\t"
// Perform the call
"movq %4, %%r11\n\t"
"movq %7, %%rax\n\t"
"call *%%r11\n\t"
// Fill the return values
"movq %%rax, %0\n\t"
"movq %%rdx, %1\n\t"
"movsd %%xmm0, %2\n\t"
"movsd %%xmm1, %3\n\t"
: "=m" ( rax ), "=m" ( rdx ), "=m" ( xmm0 ), "=m" ( xmm1 )
: "m" ( pMethod ), "m" ( pGPR ), "m" ( pFPR ), "m" ( nFPR )
: "rax", "rdi", "rsi", "rdx", "rcx", "r8", "r9", "r11"
);
Semi-off-topic, I think this asm can be better done with only the
call inside the asm, and the rest handled by the compiler.
{
register sal_uInt64 hard_r8 __asm__("rax"); // etc
register double hard_xmm0 __asm__("xmm0"); // etc
hard_rdi = pGPR[0]; //etc
hard_xmm0 = pFPR[0]; //etc
hard_rax = nFPR;
asm volatile ("call *%[method]"
: "+r"(hard_rax), //etc
"+x"(hard_xmm0), //etc
: "g" [method] (pMethod)
: "memory");
rax = hard_rax;
rdx = hard_rdx;
xmm0 = hard_xmm0;
xmm1 = hard_xmm1;
}
Of course, there's still the problem of getting the unwind data correct at
the point of the asm. I commented about that in the PR you filed.
r~
