search for: va_args

# The future of the va_arg instruction ## Summary LLVM IR currently defines a va_arg instruction, which can be used to access a vararg. Few Clang targets make use of it, and it has a number of limitations. This RFC hopes to promote discussion on its future - how 'smart' should va_arg be? Should we be aiming to transition all targets and LLVM frontends to using it? ## Background on va_arg

On 9 August 2017 at 19:38, Friedman, Eli <efriedma at codeaurora.org> wrote: > On 8/9/2017 9:11 AM, Alex Bradbury via llvm-dev wrote: >> >> Option 3: Teach va_arg to handle aggregates >> * In this option, va_arg might reasonably be expected to handle a >> struct, >> but would not be expected to have detailed ABI-specific knowledge. e.g. >> it

Hi everyone, I'm interested in variadic functions and how llvm handles them. I discovered that the Clang frontend is doing a great job at lowering the va_arg (precisely __builtin_va_arg) function into target dependent code. I have also seen the va_arg function that exist at IR level. I found some information about va_arg (IR one) that currently does not support all platform. But since 2009,

Hi! I am trying to implement va_arg() on ppc32. Everything went smooth, except implementing va_arg() of 64bit int. Since i64 is not a legal type on ppc32 DAGTypeLegalizer::ExpandRes_VAARG() splits the va_arg(i64) into two i32 va_args. The problem with ppc32 va_arg is that it needs special "alignment" of its gpr pointer when the argument is i64. Ie. I need to know if I am lowering va_arg of i64. I tried to tackle this by providing custom lowering for va_arg(i64) that just aligns stuff properly. I do this by adding I...

Hi folk, I'm writing a set of small C code to verify whether my pass handle some instruction correctly. One of the instruction I want to test is "va_arg", but compiling my variadic function does not generate any va_arg instruction. Is va_arg deprecated? Will va_arg instruction ever be generated by any front-end? The source code and llvm instructions are appended as follows. the

Hi everyone, I'm interested in variadic functions and how llvm handles them. I discovered that the Clang frontend is doing a great job at lowering the va_arg (precisely __builtin_va_arg) function into target dependent code. I have also seen the va_arg function that exist at IR level. I found some information about va_arg (IR one) that currently does not support all platform. But since 2009,

To get clang to emit va_arg instructions for va_arg() calls, as opposed to manually lowering it in the frontend, same as the llvm-gcc patch sent earlier does. ~Will On Wed, Aug 17, 2011 at 2:41 PM, Eric Christopher <echristo at apple.com> wrote: > > On Aug 17, 2011, at 11:53 AM, Will Dietz wrote: > >> FWIW, attached is a similar patch that adds a -falways-use-llvm-vaarg

I should have been more specific: "Why do we want this as an option? Do we want it on all the time? Why or why not?" -eric On Aug 17, 2011, at 3:02 PM, Will Dietz wrote: > To get clang to emit va_arg instructions for va_arg() calls, as > opposed to manually lowering it in the frontend, same as the llvm-gcc > patch sent earlier does. > > ~Will > > On Wed, Aug

Neal, FYI, my group has added a flag to llvm-gcc for emitting the va_arg instruction (instead of lowering in the front-end), and we also have an implementation of the VAARG instruction for X86-64. (which is currently not implemented in the LLVM backend). Both of these things will be sent upstream to LLVM soon, pending some more testing and review. If you are dire need of these features now, I

Oh, sorry about that, and thanks for the clarification as to what you were looking for. Here you go: ** Why do we want this option? ** Presently clang will manually lower va_arg() in the frontend to the equivalent (relatively complicated!) IR, as opposed to making use of the LLVM va_arg instruction directly. IR that contains the va_arg instruction is much easier to analyze because it is

Dear all, Is there a way to have llvm-gcc output the llvm va_arg intrinsic? As far as I understand, llvm-gcc directly lowers va_arg in the frontend using the TARGET_GIMPLIFY_VA_ARG target hook. I am aware that va_arg segfaults on x86-64 (http://llvm.org/bugs/show_bug.cgi?id=1740) and that llvm-gcc avoids this issue by always lowering calls to va_arg

Hi all, I am currently writing an obfuscation pass (on LLVM 3.3 code base) that works at IR level and that implement procedures fusion. For this, I am heavily relying on the va_arg intrinsic. My code is functional when compiled with no optimization (-O0), but I experience strange behavior when compiling with -O2 or -O3. I am currently using the libgmp and OpenSSL libraries test suites. I know

...on Sparc processors (specifically, LEON, but I suspect but can't verify that it also happens on all Sparc processors). The problem is, or appears to be with using double values in Sparc (32 bit). Specifically, double values are not being loaded into registers correctly within a function using va_args. Only half the value is loaded (i.e. 32, rather than 64 bits of the value). What I have also found is that the failure does not happen in all circumstances. The simplest situation I've been able to re-create that avoids the problem is to put a store and subsequent load instruction around the v...

/* * Copyright (c) 1983, 1995, 1996 Eric P. Allman * Copyright (c) 1988, 1993 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of

I would like to be able to instrument va_arg, but when I generate a bc file for a test case using: llvm-gcc -O3 -emit-llvm vararg.c -c -o vararg.bc I do not see va_arg. Instead, it seems the args are accessed through %struct.__va_list_tag, which makes things a bit trickier to instrument. Is there a way to force llvm-gcc to use va_arg? Perhaps there is some documentation about va_list_tag or

For the variadic function error with AMD64 abi and windows calling convention on 64bits x86, I find it has been tracked in Bug 20847 (https://llvm.org/bugs/show_bug.cgi?id=20847) (http://reviews.llvm.org/D1622#inline-9345). Do we still plan to fix it? You know, I meet exactly same va_arg mistake with llvm3.7 when I enable the Uefi firmware (http://www.uefi.org/) build with clang. The ms_abi is

Provide a full-fledged example of working variable arguments on X86_64, since it's easily the most popular platform. Cc: Reid Kleckner <rnk at google.com> Signed-off-by: Ramkumar Ramachandra <artagnon at gmail.com> --- docs/LangRef.rst | 44 ++++++++++++++++++++++++++++++-------------- 1 file changed, 30 insertions(+), 14 deletions(-) diff --git a/docs/LangRef.rst

hi,      I am porting llvm to our embedded cpu. By my abi, long long type is aligned by 8 bytes. But now llvm-gcc frontend follows x86 abi, generate word-alignment LLVM-IR for va_arg().    In some degree, llvm-gcc frontend depends on targets. The best solution is llvm-gcc can create va_arg node, I can lower it at the backend.    Who can give a temporary solution to make frontend can create 8

FWIW, attached is a similar patch that adds a -falways-use-llvm-vaarg flag to Clang. Applies against mainline. (As discussed, va_arg isn't really supported well so this probably doesn't work well on anything other than simple code, YMMV, etc) ~Will On Thu, May 12, 2011 at 12:29 PM, Arushi Aggarwal <arushi987 at gmail.com> wrote: > Have these changes made it to mainline? Is

On Aug 17, 2011, at 11:53 AM, Will Dietz wrote: > FWIW, attached is a similar patch that adds a -falways-use-llvm-vaarg > flag to Clang. > > Applies against mainline. > > (As discussed, va_arg isn't really supported well so this probably > doesn't work well on anything other than simple code, YMMV, etc) > > ~Will > > On Thu, May 12, 2011 at 12:29 PM,