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digitalmars.D.learn - RDTSCP from dlang

reply kookman <thekookman gmail.com> writes:
I need to access the x86_64 RDTSCP assembly instruction from D.

I found this for C++:
http://stackoverflow.com/questions/14783782/which-inline-assembly-code-is-correct-for-rdtscp

Does anyone here know how (if?) I can do this from D?
Aug 29 2016
next sibling parent rikki cattermole <rikki cattermole.co.nz> writes:
On 30/08/2016 2:04 PM, kookman wrote:

 I need to access the x86_64 RDTSCP assembly instruction from D.

 I found this for C++:
 http://stackoverflow.com/questions/14783782/which-inline-assembly-code-is-correct-for-rdtscp


 Does anyone here know how (if?) I can do this from D?


It appears dmd's inline assembler does not support it.

So a workaround:

asm {
	// rdtscp
	db 0x0F;
	db 0x01;
	db 0xF9;
}

http://dlang.org/spec/iasm.html
Aug 29 2016
prev sibling parent reply Basile B. <b2.temp gmx.com> writes:
On Tuesday, 30 August 2016 at 02:04:55 UTC, kookman wrote:

 I need to access the x86_64 RDTSCP assembly instruction from D.

 I found this for C++:
 http://stackoverflow.com/questions/14783782/which-inline-assembly-code-is-correct-for-rdtscp

 Does anyone here know how (if?) I can do this from D?


ALternatively to Rikki K's solution, you can do this to mimic the 
rdtscp behavior:

asm
{
   cpuid;
   rdtsc;
   // store time in locals
}
// bench
{
   rdtsc;
   // store time in locals
}
// compute delta


explanations here:
- 
http://www.intel.com/content/dam/www/public/us/en/documents/white-papers/ia-32-ia-64-benchmark-code-execution-paper.pdf
- http://stackoverflow.com/a/14214220

But according to the first link, this solution, while better than 
rdtsc alone, is not as good as rdtscp.
Aug 30 2016
parent reply kookman <thekookman gmail.com> writes:
On Tuesday, 30 August 2016 at 09:04:41 UTC, Basile B. wrote:

 ALternatively to Rikki K's solution, you can do this to mimic 
 the rdtscp behavior:

 asm
 {
   cpuid;
   rdtsc;
   // store time in locals
 }
 // bench
 {
   rdtsc;
   // store time in locals
 }
 // compute delta


 explanations here:
 - 
 http://www.intel.com/content/dam/www/public/us/en/documents/white-papers/ia-32-ia-64-benchmark-code-execution-paper.pdf
 - http://stackoverflow.com/a/14214220

 But according to the first link, this solution, while better 
 than rdtsc alone, is not as good as rdtscp.


Indeed, I want to use rdtscp to get access to the core ID it 
makes available (to at least know when tsc is from different 
cores/packages). I guess in the meantime I can use Rikki's 
solution.

Sorry I'm a DMD asm newbie: DO i need to worry about which 
registers I clobber here? I couldn't find any info about this on 
the Inline Assembly doco page on dlang.org.
Aug 31 2016
next sibling parent reply rikki cattermole <rikki cattermole.co.nz> writes:
On 31/08/2016 7:34 PM, kookman wrote:

 On Tuesday, 30 August 2016 at 09:04:41 UTC, Basile B. wrote:

 ALternatively to Rikki K's solution, you can do this to mimic the
 rdtscp behavior:

 asm
 {
   cpuid;
   rdtsc;
   // store time in locals
 }
 // bench
 {
   rdtsc;
   // store time in locals
 }
 // compute delta


 explanations here:
 -
 http://www.intel.com/content/dam/www/public/us/en/documents/white-papers/ia-32-ia-64-benchmark-code-execution-paper.pdf

 - http://stackoverflow.com/a/14214220

 But according to the first link, this solution, while better than
 rdtsc alone, is not as good as rdtscp.


 Indeed, I want to use rdtscp to get access to the core ID it makes
 available (to at least know when tsc is from different cores/packages).
 I guess in the meantime I can use Rikki's solution.

 Sorry I'm a DMD asm newbie: DO i need to worry about which registers I
 clobber here? I couldn't find any info about this on the Inline Assembly
 doco page on dlang.org.


http://dlang.org/spec/abi.html#register_conventions
Aug 31 2016
parent reply kookman <thekookman gmail.com> writes:
On Wednesday, 31 August 2016 at 07:36:16 UTC, rikki cattermole 
wrote:


 http://dlang.org/spec/abi.html#register_conventions


That link talks about for functions defined extern(C) and 
extern(D), and gives specific info for win32.

I'm using linux x86_64, does that mean I can assume standard 
x86_64 ABI? ie even if the function is not extern?
Aug 31 2016
parent rikki cattermole <rikki cattermole.co.nz> writes:
On 31/08/2016 7:49 PM, kookman wrote:

 On Wednesday, 31 August 2016 at 07:36:16 UTC, rikki cattermole wrote:


 http://dlang.org/spec/abi.html#register_conventions


 That link talks about for functions defined extern(C) and extern(D), and
 gives specific info for win32.

 I'm using linux x86_64, does that mean I can assume standard x86_64 ABI?
 ie even if the function is not extern?


That link describes extern(D) for x86(_64) for all platforms. Keep in 
mind if a function body does not have an extern(X) supplied, the default 
is extern(D).

C is listed there as we have first class C interaction via extern(C).

The listing of DLL's on that page really should be changed to dynamic 
libraries. Since that covers linuxes.
Aug 31 2016
prev sibling parent reply Basile B. <b2.temp gmx.com> writes:
On Wednesday, 31 August 2016 at 07:34:14 UTC, kookman wrote:

 On Tuesday, 30 August 2016 at 09:04:41 UTC, Basile B. wrote:
 Indeed, I want to use rdtscp to get access to the core ID it 
 makes available (to at least know when tsc is from different 
 cores/packages). I guess in the meantime I can use Rikki's 
 solution.

 Sorry [...]


Never mind, I know Rikki's solution is better but since I've read 
a bit of doc and found this alternative I've just posted the 
alternative.

By the way maybe someone could post an ER in bugzilla to get 
RDTSCP available in iasm w/o using the byte code trick.
Aug 31 2016
parent kookman <thekookman gmail.com> writes:
On Wednesday, 31 August 2016 at 08:23:57 UTC, Basile B. wrote:


 By the way maybe someone could post an ER in bugzilla to get 
 RDTSCP available in iasm w/o using the byte code trick.


Someone beat me to it, but see here:
https://issues.dlang.org/show_bug.cgi?id=16449
Aug 31 2016