Hello, LLVMers!
How can I force a front end to generate VAARG for accessing varargs parameters?
I compile a simple C-code:
#include <stdarg.h>
int FnVarArgs(int a, …)
{
int i,tmp=0;
va_list ptArgument;
va_start(ptArgument,a);
for(i=0;i<9;i++)
tmp+= va_arg(ptArgument,int);
return tmp;
}
And then have this bytecode:
; ModuleID = ‘main.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”
target triple = “i386-pc-linux-gnu”
define i32 @FnVarArgs(i32 %a, …) nounwind {
bb2.thread:
%ptArgument = alloca i8*, align 4 ; <i8**> [#uses=3]
%ptArgument1 = bitcast i8** %ptArgument to i8* ; <i8*> [#uses=1]
call void @llvm.va_start(i8* %ptArgument1)
br label %bb2
bb2: ; preds = %bb2, %bb2.thread
%i.0.reg2mem.0 = phi i32 [ 0, %bb2.thread ], [ %indvar.next, %bb2 ] ; [#uses=1]
%tmp.0.reg2mem.0 = phi i32 [ 0, %bb2.thread ], [ %4, %bb2 ] ; [#uses=1]
%0 = load i8** %ptArgument, align 4 ; <i8*> [#uses=2]
%1 = getelementptr i8* %0, i32 4 ; <i8*> [#uses=1]
store i8* %1, i8** %ptArgument, align 4
%2 = bitcast i8* %0 to i32* ; <i32*> [#uses=1]
%3 = load i32* %2, align 4 ; [#uses=1]
%4 = add i32 %3, %tmp.0.reg2mem.0 ; [#uses=2]
%indvar.next = add i32 %i.0.reg2mem.0, 1 ; [#uses=2]
%exitcond = icmp eq i32 %indvar.next, 9 ; [#uses=1]
br i1 %exitcond, label %bb3, label %bb2
bb3: ; preds = %bb2
ret i32 %4
}
declare void @llvm.va_start(i8*) nounwind
There is a call of “va_start” and there isn’t any “va_arg“! But I need it for specifical lower in back end for my target!
Thanks,
–Artem