[LLVMdev] Is va_arg deprecated?

[Neal N. Wang]

Thanks David, I don't want my pass to get any surprise when some front-ends
emit va_arg.  Can you please point out the link of your beta versions?
Thanks, Neal.

On Mon, Jul 19, 2010 at 2:18 PM, David Meyer <pdox at google.com> wrote:

> 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 can point you to the
> (public) repository where we have the beta versions.
>
> - David M
>
>
> On Mon, Jul 19, 2010 at 11:57 AM, Neal  N. Wang <neal.wang at gmail.com>
> wrote:
> > 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 c code
> > #include<stdarg.h>
> > #include<stdio.h>
> > #include<stdlib.h>
> >
> > void printValue(char * fmt, ...) {
> >   va_list args;
> >   va_start(args, fmt);
> >   int i;
> >   double d;
> >   i = va_arg(args, int);
> >   d = va_arg(args, double);
> >   va_end(args);
> > }
> >
> > the generated llvm instructions:
> > ; ModuleID = 'i.bc'
> > target datalayout =
> >
> "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
> > target triple = "i386-pc-linux-gnu"
> >
> > define void @printValue(i8* %fmt, ...) nounwind {
> > entry:
> >   %fmt_addr = alloca i8*                          ; <i8**> [#uses=1]
> >   %args.2 = alloca i8*                            ; <i8**> [#uses=3]
> >   %args.0 = alloca i8*                            ; <i8**> [#uses=3]
> >   %args = alloca i8*                              ; <i8**> [#uses=6]
> >   %i = alloca i32                                 ; <i32*> [#uses=1]
> >   %d = alloca double, align 8                     ; <double*> [#uses=1]
> >   %"alloca point" = bitcast i32 0 to i32          ; <i32> [#uses=0]
> >   store i8* %fmt, i8** %fmt_addr
> >   %args1 = bitcast i8** %args to i8*              ; <i8*> [#uses=1]
> >   call void @llvm.va_start(i8* %args1)
> >   %0 = load i8** %args, align 4                   ; <i8*> [#uses=1]
> >   store i8* %0, i8** %args.0, align 4
> >   %1 = load i8** %args.0, align 4                 ; <i8*> [#uses=1]
> >   %2 = getelementptr inbounds i8* %1, i64 4       ; <i8*> [#uses=1]
> >   store i8* %2, i8** %args, align 4
> >   %3 = load i8** %args.0, align 4                 ; <i8*> [#uses=1]
> >   %4 = bitcast i8* %3 to i32*                     ; <i32*> [#uses=1]
> >   %5 = load i32* %4, align 4                      ; <i32> [#uses=1]
> >   store i32 %5, i32* %i, align 4
> >   %6 = load i8** %args, align 4                   ; <i8*> [#uses=1]
> >   store i8* %6, i8** %args.2, align 4
> >   %7 = load i8** %args.2, align 4                 ; <i8*> [#uses=1]
> >   %8 = getelementptr inbounds i8* %7, i64 8       ; <i8*> [#uses=1]
> >   store i8* %8, i8** %args, align 4
> >   %9 = load i8** %args.2, align 4                 ; <i8*> [#uses=1]
> >   %10 = bitcast i8* %9 to double*                 ; <double*> [#uses=1]
> >   %11 = load double* %10, align 4                 ; <double> [#uses=1]
> >   store double %11, double* %d, align 8
> >   %args2 = bitcast i8** %args to i8*              ; <i8*> [#uses=1]
> >   call void @llvm.va_end(i8* %args2)
> >   br label %return
> >
> > return:                                           ; preds = %entry
> >   ret void
> > }
> >
> > declare void @llvm.va_start(i8*) nounwind
> >
> > declare void @llvm.va_end(i8*) nounwind
> >
> >
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >
> >
>
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