Displaying 6 results from an estimated 6 matches for "divq".
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2017 Oct 19
2
Why x86_64 divq is not used for 128-bit by 64-bit division?
Hi there,
Let's have this C code:
unsigned long div(unsigned __int128 n, unsigned long d)
{
return n / d;
}
I would assume that the divq is the perfect match here. But the compiler
generates the
code that calls the __udivti3 procedure which performs 128-bit by 128-bit
division.
Why is divq not used here?
- Paweł
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2010 Mar 25
0
Blackfin inline assembly for fixed math
..."R0 = %1;\n\t"
"R1 = %2;\n\t"
//"R0 = R0 + R1;\n\t"
"R0 <<= 1;\n\t"
"DIVS (R0, R1);\n\t"
"LOOP divide%= LC0 = P0;\n\t"
"LOOP_BEGIN divide%=;\n\t"
"DIVQ (R0, R1);\n\t"
"LOOP_END divide%=;\n\t"
"R0 = R0.L;\n\t"
"%0 = R0;\n\t"
: "=m" (res)
: "m" (a), "m" (bb)
: "P0", "R0", "R1", "cc");
return res;
}
#undef D...
2016 Dec 10
2
Interest in integrating a linux perf JITEventListener?
Hi,
Under linux a large portion of the profiling these days happens with
perf, but there's no support for it from LLVM's JITs.
For a while perf could associate address+size to symbols by writing a
/tmp/perf-$pid.map file:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/tools/perf/Documentation/jit-interface.txt
A year or so perf also gained the ability to actually
2017 Feb 02
0
Interest in integrating a linux perf JITEventListener?
...30:│ addq $0x2,-0x18(%rbp)
4.03 │1 35:│ mov -0x10(%rbp),%rax
0.06 │ │ shr %rax
│ │ cmp %rax,-0x18(%rbp)
│ └──jae e
│ if (num % i == 0)
3.74 │ mov -0x10(%rbp),%rax
0.09 │ xor %edx,%edx
91.82 │ divq -0x18(%rbp)
│ test %rdx,%rdx
0.23 │ ↑ jne 30
0.03 │2 51: movb $0x0,-0x1(%rbp)
│1 55: mov -0x1(%rbp),%al
│ pop %rbp
│ ← retq
(the missing colors make it harder to see what's going on)
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2018 Mar 26
0
Interest in integrating a linux perf JITEventListener?
...3 │1 35:│ mov -0x10(%rbp),%rax
> 0.06 │ │ shr %rax
> │ │ cmp %rax,-0x18(%rbp)
> │ └──jae e
> │ if (num % i == 0)
> 3.74 │ mov -0x10(%rbp),%rax
> 0.09 │ xor %edx,%edx
> 91.82 │ divq -0x18(%rbp)
> │ test %rdx,%rdx
> 0.23 │ ↑ jne 30
> 0.03 │2 51: movb $0x0,-0x1(%rbp)
> │1 55: mov -0x1(%rbp),%al
> │ pop %rbp
> │ ← retq
>
> (the missing colors make it harder to see what's going...
2016 Dec 29
1
Interest in integrating a linux perf JITEventListener?
Having something like this available in tree would definitely be
useful. For simplicity, why don't we start with support for the second
style? This is the long term useful one and would be a good starting
point for getting the code in tree. Can you give a pointer to the patch
so that I can assess the rough complexity? If it's simple enough, I'd
be happy to help get it reviewed