Assiging 0.0s to an array gives memset error

[ipcamit]

Issue:
I get the following error:

error: Enzyme: Cannot deduce type of memset   call void @llvm.memset.p0.i64(ptr noundef nonnull align 4 dereferenceable(108) %3, i8 0, i64 108, i1 false) #7
<analysis>
ptr %0: {[-1]:Pointer}, intvals: {}
ptr %1: {[-1]:Pointer}, intvals: {}
ptr %2: {[-1]:Pointer}, intvals: {}
ptr %3: {[-1]:Pointer}, intvals: {}
</analysis>

in function:

void irreps_to_out(float* x_, float* y_, float* z_, float* out_feature){
    float x = *x_; float y = *y_; float z = *z_;

    float *product = (float*) malloc(27 * sizeof(float));
    for(int i = 0; i < 27; i++) { product[i] = 0.0; }  // <--- Problematic line
    for(int i = 0; i < 27; i++) { out_feature[i] = product[i]; }
}

Issue is specifically that the compiler optimizes this assignment to a memset call if assigned value is 0.0. For any other assignment like

    for(int i = 0; i < 27; i++) { product[i] = 0.0000000000001; }  // <--- Problematic line

it compiles fine.

It also compiles if I give option -O0 thus avoiding optimization of assignment to memset.

---

Enzyme Explorer:

https://fwd.gymni.ch/ecQeCs

---

Full example:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

void irreps_to_out(float* x_, float* y_, float* z_, float* out_feature)
{
    float x = *x_;
    float y = *y_;
    float z = *z_;

    // float product[27];
    float *product = (float*) malloc(27 * sizeof(float));
    for(int i = 0; i < 27; i++) { product[i] = 0.0; }  // <--- Problematic line
    for(int i = 0; i < 27; i++) { out_feature[i] = product[i]; }

}

int enzyme_dup;

void __enzyme_autodiff(void (*) (float*, float*, float*, float*), 
                        int, float*, float*,
                        int, float*, float*, 
                        int, float*, float*,
                        int, float*, float*);

int main(){
    float out_feature[27] = { 0., 0., 0.,0., 0., 0.,0., 0., 0.,
                               0., 0., 0.,0., 0., 0.,0., 0., 0.,
                                0., 0., 0.,0., 0., 0.,0., 0., 0. };
    float out_grad[27] = {1., 1., 1., 1., 1., 1., 1., 1., 1.,
                          1., 1., 1., 1., 1., 1., 1., 1., 1.,
                          1., 1., 1., 1., 1., 1., 1., 1., 1.};

    float x = 1.0, y = 2.0, z = 3.0;
    float x_grad = 0.0, y_grad = 0.0, z_grad = 0.0;
    irreps_to_out(&x, &y, &z, out_feature);
   
    __enzyme_autodiff(irreps_to_out, 
                        enzyme_dup, &x, &x_grad, 
                        enzyme_dup, &y, &y_grad, 
                        enzyme_dup, &z, &z_grad, 
                        enzyme_dup, out_feature, out_grad);

    return 0;
}

compiled as

clang example.c  -Xclang -load -Xclang /path/to/ClangEnzyme-15.so -lm -O3

clang -v

clang version 15.0.7 (https://github.com/conda-forge/clangdev-feedstock 7546975a4a926b2b6b05f442d73827ff01b1ae76)
Target: x86_64-conda-linux-gnu
Thread model: posix
InstalledDir: /opt/mambaforge/mambaforge/envs/e3nn/bin
Found candidate GCC installation: /opt/mambaforge/mambaforge/envs/e3nn/bin/../lib/gcc/x86_64-conda-linux-gnu/14.1.0
Selected GCC installation: /opt/mambaforge/mambaforge/envs/e3nn/bin/../lib/gcc/x86_64-conda-linux-gnu/14.1.0
Candidate multilib: .;@m64
Selected multilib: .;@m64

Enzyme commit: 192d9231aaa5415fa135ffb3568cc8eceef512d5