[cfe-users] Getting variable names in LLVM IR

[Duncan Exon Smith via cfe-users]

> On Feb 14, 2017, at 22:27, Subhendu Malakar <subhendu.m.x1 at gmail.com> wrote:
> 
> Thanks for the reply.
> 
> Indeed, I was not building "clang" from source. I'm going to build it now.
> 
> Just curious to know if it is possible to negate the option "discard-value-names" like "no-discard-value-names", etc. such that I don't have to copy paste the whole thing again and again. Couldn't find any such option in "clang -cc1 --help".

No, but there probably should be.  Same with similar options like -disable-free and -disable-llvm-verifier. 

Feel free to file a bug at bugs.llvm.org and CC me.

> 
> Thanks.
> 
> On Wednesday 15 February 2017 05:44 AM, Duncan P. N. Exon Smith wrote:
>>> On 2017-Feb-13, at 23:10, Subhendu Malakar via cfe-users <cfe-users at lists.llvm.org> wrote:
>>> 
>>> Hi,
>>> I'm a newbie in LLVM environment.
>>> 
>>> I'm trying to generate the LLVM IR of a c file using clang. The command line argument I'm passing is as :
>>> "clang -O0 -S -emit-llvm test.c -c -o test.ll"
>> If you add "-###" to the end of the command-line you can see the raw -cc1 command for the compilation.  Depending on your version of clang, you should see "-discard-value-names" in there.  If you repeat the -cc1 command yourself, skipping that option, you'll get variable names.
>> 
>> If you're compiling clang yourself (it doesn't sound like you are, but just in case), this -discard-value-names option is *not* passed by default in asserts builds.
>> 
>>> It is generating the LLVM IR properly but I'm not getting the variable names. e.g,
>>> 
>>> for the c file :
>>> #include <stdio.h>
>>> 
>>> int main()
>>> {
>>>    int x;
>>>    int y;
>>>    x = 2;
>>>    y =4;
>>>    int z = x*y;
>>> 
>>>    if(x==y)
>>>    {
>>>        z = x*y;
>>>        return z;
>>>    } else
>>>    {
>>>        z = x+y;
>>>    }
>>>    printf("z = %d", z);
>>>    return 0;
>>> }
>>> 
>>> 
>>> the corresponding llvm IR is :
>>> 
>>> ; Function Attrs: nounwind uwtable
>>> define i32 @main() #0 {
>>>  %1 = alloca i32, align 4
>>>  %2 = alloca i32, align 4
>>>  %3 = alloca i32, align 4
>>>  %4 = alloca i32, align 4
>>>  store i32 0, i32* %1, align 4
>>>  store i32 2, i32* %2, align 4
>>>  store i32 4, i32* %3, align 4
>>>  %5 = load i32, i32* %2, align 4
>>>  %6 = load i32, i32* %3, align 4
>>>  %7 = mul nsw i32 %5, %6
>>>  store i32 %7, i32* %4, align 4
>>>  %8 = load i32, i32* %2, align 4
>>>  %9 = load i32, i32* %3, align 4
>>>  %10 = icmp eq i32 %8, %9
>>>  br i1 %10, label %11, label %16
>>> 
>>> ; <label>:11:                                     ; preds = %0
>>>  %12 = load i32, i32* %2, align 4
>>>  %13 = load i32, i32* %3, align 4
>>>  %14 = mul nsw i32 %12, %13
>>>  store i32 %14, i32* %4, align 4
>>>  %15 = load i32, i32* %4, align 4
>>>  store i32 %15, i32* %1, align 4
>>>  br label %21
>>> 
>>> ; <label>:16:                                     ; preds = %0
>>>  %17 = load i32, i32* %2, align 4
>>>  %18 = load i32, i32* %3, align 4
>>>  %19 = add nsw i32 %17, %18
>>>  store i32 %19, i32* %4, align 4
>>>  br label %20
>>> 
>>> ; <label>:20:                                     ; preds = %16
>>>  store i32 0, i32* %1, align 4
>>>  br label %21
>>> 
>>> ; <label>:21:                                     ; preds = %20, %11
>>>  %22 = load i32, i32* %1, align 4
>>>  ret i32 %22
>>> }
>>> 
>>> 
>>> I wanted to get the variables in their original name i.e, x,y,z instead of %1,%2,%3, etc.
>>> Is it possible to do so?
>>> 
>>> Thanks.
>>> _______________________________________________
>>> cfe-users mailing list
>>> cfe-users at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-users
>