Description
According to me, the following code changes the third value of the buffer. However, it changes the first value when using the nvidia 460.80 driver under ubuntu 21.1.
Initialization values of the buffer are given by the comments.
#version 310 es
layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
layout(std430, binding = 0) buffer buffer_0 {
int ext_2[3]; // 2 0 -2
int ext_3[1]; // -2147483648
} ;
int return_zero() //return 0
{
return 0;
}
void set_1(inout int A, int B) //set 1
{
return A = 1;
}
void main()
{
set_1(ext_2[clamp(~ext_3[0], 0, 2)], ext_3[return_zero()] += -2147483648);
}
Nvidia output:
buffer_0 1 0 -2 0
Expected output:
buffer_0 2 0 1 0
Thinking process:
- set_1 the value on the left argument (a position in ext_2) to 1, the second parameter is unused.
- the position is given by clamp(~ext_3[0],0,2) where ext_3[0] = -2147483648
- ~ext_3[0] = 2147483647 so that clamp(~ext_3[0],0,2)=2
From what I understand from the OpenGL ES 3.1 specification (6.1.1 Function Calling Conventions), parameters should be evaluated from left to right, so that the side effect on the second parameter should have no effect to the position in the first parameter.
Code links
For the related code in the shadertrap test format, see: nvidia/miscompilation/shader02.shadertrap or shader02.shadertrap (812 Bytes).
Compute shader only:
shader02.comp (396 Bytes)
