similar to: [LLVMdev] Var Args on X86-64

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,

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

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

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,

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

On Tue, 3 Apr 2007, Nicolas Geoffray wrote: > A VAARG call requires a lot of computation. Typically the C code for > va_arg(ap, int) If you use va_arg in C, are you seeing llvm.vaarg in the output .ll file? -Chris > is: > > int va_arg_gpr(ap_list ap) { > int idx = ap->gpr; > if (idx < 8) { > ap->gpr = idx + 1; > return

Hi everyone, I'm implementing varags handling for PPC32 with the ELF ABI. It is largely more complicated than the Macho ABI or x86 because it manipulates a struct instead of a direct pointer in the stack. You can find the layout of the va_list struct at the end of this mail. A VAARG call requires a lot of computation. Typically the C code for va_arg(ap, int) is: int va_arg_gpr(ap_list

When I use clang on an x86-64 to spit out the LLVM, like this clang -O -S -emit-llvm varargstest.c where varargstest.c looks like this int add_em_up(int count, ...) { va_list ap; int i, sum; va_start(ap, count); sum = 0; for (i = 0; i < count; i++) sum += va_arg(ap, int); va_end(ap); return sum; } I see LLVM that looks like it's been customized for the x86-64, versus

Hi Chris, Chris Lattner wrote: > On Tue, 3 Apr 2007, Nicolas Geoffray wrote: > >> A VAARG call requires a lot of computation. Typically the C code for >> va_arg(ap, int) >> > > If you use va_arg in C, are you seeing llvm.vaarg in the output .ll file? > I'm guessing that if you're asking, then no llvm.vaarg is generated. I can not test it on my

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

# 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

I'm generating code for a target that only supports i32 natively. My front end is generating VAARG for accessing varargs parameters. The problem is that I get an assert when I compile this: #include <stdarg.h> int main(va_list ap) { typedef double type; type tmp; tmp = va_arg(ap, type); } Bitcode: ; ModuleID = 't0056.bc' target datalayout =

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 David, I'm working on source to source transformations and instrumentation. A flag to disable 'va_arg' lowering in LLVM FEs will be very useful. Have you sent your modifications upstream to LLVM? If not, could you please share link to your public repository. Thanks, Sergey Yakoushkin On Mon, Jul 19, 2010 at 11:18 PM, David Meyer <pdox at google.com> wrote: > Neal, >

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

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

I tried to compile on Windows ( using the win32/llvm.sln in MSVC Express 2008 ) the new 2.3 branch and here are the results: 1. I needed to copy the file Configure.exe.embed.manifest to Configure.exe.intermediate.manifest . This is a bug from the previous llvm release (2.2) 2. I copied the file SimplifyLibCalls.cpp from lib/Transforms/Scalar to lib/Transforms/IPO. I think the position of

Sergey, Here's a patch on llvm-gcc which adds a flag "-fuse-llvm-va-arg". (Note that this patch won't ever be part of llvm-gcc upstream. It will most likely be deprecated by later changes.) - pdox -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20110220/f814866f/attachment.html>

Have these changes made it to mainline? Is there a way to get a patch for the backend, which does the actual lowering? Thanks, Arushi On Sun, Feb 20, 2011 at 1:54 PM, David Meyer <pdox at google.com> wrote: > Sergey, > Here's a patch on llvm-gcc which adds a flag "-fuse-llvm-va-arg". > (Note that this patch won't ever be part of llvm-gcc upstream. It will most