This code is written in LLVM Intermediate Representation (IR) and...

This code is written in LLVM Intermediate Representation (IR) and performs the following operations:

1. First line:

   %vec = load <4 x i32>, ptr %arg
   

   • This line loads a 128-bit vector (4 elements of 32-bit integers, <4 x i32>), from the memory address pointed to by %arg into the %vec variable.
   • %arg is expected to be a pointer to this vector.

2. Second line:

   %hadd = tail call i32 @llvm.vector.reduce.add.v4i32(<4 x i32> %vec)
   

   • This line calls the LLVM intrinsic function @llvm.vector.reduce.add.v4i32, which performs a horizontal addition (or reduction) of the elements in the vector %vec.

   • Specifically, the elements of the vector (<4 x i32>) are added together to compute a single scalar integer result (i32).

   • The sum is stored in the %hadd variable.

   • The tail keyword indicates that the call is a tail call, meaning that it can be optimized by a compiler to avoid creating a new stack frame for the function call.

Example:

If %vec contains the vector <1, 2, 3, 4>, the intrinsic function @llvm.vector.reduce.add.v4i32 will compute 1 + 2 + 3 + 4 = 10.

Summary:

This code snippet:

1. Loads a vector of 4 integers from memory.
2. Computes the sum of all 4 elements in the vector using LLVM's horizontal reduction intrinsic. The result is stored in %hadd.