And are such intrinsics, as memset, memcpy, memmove replaced by standard library calls? This is said in sources, that it looks for such functions in global symbol table. 2017-07-11 20:16 GMT+02:00 Friedman, Eli <efriedma at codeaurora.org>:> On 7/11/2017 10:26 AM, Anastasiya Ruzhanskaya via llvm-dev wrote: > >> Hello, >> I would like to find out a detail about intrinsics functions. When I use >> memset form a standard library it is always converted to llvm's memset, >> however the usage of some others as sqrt, pow, sin do not lead to the same. >> How can I get the same effect? >> > > For math functions in particular, the intrinsics don't really match the > semantics of the actual C library functions, so clang doesn't normally > convert them. (If you use -ffast-math, clang will convert them anyway.) > This is an area which could probably be improved, but it's complicated > because we depend on the host's libm. > > Why there is no overall LLVM pass like IntrinsicLowerinPass.cpp (it has >> only some specific ones)? There is only a function that does this. >> > > Some intrinsics expose functionality which can't be expressed using IR > instructions. > > -Eli > > -- > Employee of Qualcomm Innovation Center, Inc. > Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux > Foundation Collaborative Project > >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20170711/cd8888f7/attachment.html>
On 7/11/2017 11:19 AM, Anastasiya Ruzhanskaya wrote:> And are such intrinsics, as memset, memcpy, memmove replaced by > standard library calls? This is said in sources, that it looks for > such functions in global symbol table. >The backend will sometimes generate a call to the C library memset, memcpy, or memmove to lower a call to the LLVM intrinsics with the same name. Depending on the target/optimization flags/length of the operation, in some cases it will generate inline code, or generate a call to a function with a different name. -Eli -- Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20170711/f495eb62/attachment.html>
great, thank you!
Still, I have tried fast option:
clang -S -O3 -mllvm -ffast-math -emit-llvm sqrt.c -o sqrt.s
and also with specifying this option in opt (not in clang) - it stays the
same sqrt.
#include <stdlib.h>
#include <stdio.h>
int main() {
int a;
scanf("%d", &a);
double b = sqrt(a);
int c = (b > 10) ? 1 : 0;
return c;
}
2017-07-11 20:33 GMT+02:00 Friedman, Eli <efriedma at codeaurora.org>:
> On 7/11/2017 11:19 AM, Anastasiya Ruzhanskaya wrote:
>
> And are such intrinsics, as memset, memcpy, memmove replaced by standard
> library calls? This is said in sources, that it looks for such functions in
> global symbol table.
>
>
> The backend will sometimes generate a call to the C library memset,
> memcpy, or memmove to lower a call to the LLVM intrinsics with the same
> name. Depending on the target/optimization flags/length of the operation,
> in some cases it will generate inline code, or generate a call to a
> function with a different name.
>
> -Eli
>
> --
> Employee of Qualcomm Innovation Center, Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux
Foundation Collaborative Project
>
>
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