[llvm-dev] Find loops in LLVM bytecode

[Michael Kruse via llvm-dev]

Hi,

another suggestion is to look at Polly (http://polly.llvm.org/) for
loop analysis. It would extract high-level information such as:

$ cat ml.c
int foo() {
    int sum = 0;
    for (int i=0; i<1000; i++)
        sum += (float)i;
    return sum;
}

$ bin\clang.exe ml.c -mllvm -polly -O3 -mllvm
-polly-detect-unprofitable -mllvm -debug -mllvm
-debug-only=polly-scops -c
    Function: foo
    Region: %for.inc---%for.end
    Max Loop Depth:  1
    Context:
    {  :  }
    Assumed Context:
    {  :  }
    Boundary Context:
    {  :  }
    Arrays {
        i32 MemRef_sum_04__phi[*] // Element size 4
        i32 MemRef_conv2[*] // Element size 4
    }
    Arrays (Bounds as pw_affs) {
        i32 MemRef_sum_04__phi[*] // Element size 4
        i32 MemRef_conv2[*] // Element size 4
    }
    Alias Groups (0):
        n/a
    Statements {
        Stmt_for_inc
            Domain :=
                { Stmt_for_inc[i0] : i0 <= 999 and i0 >= 0 };
            Schedule :=
                { Stmt_for_inc[i0] -> [i0] };
            MustWriteAccess :=  [Reduction Type: NONE] [Scalar: 1]
                { Stmt_for_inc[i0] -> MemRef_sum_04__phi[] };
            ReadAccess :=       [Reduction Type: NONE] [Scalar: 1]
                { Stmt_for_inc[i0] -> MemRef_sum_04__phi[] };
            MustWriteAccess :=  [Reduction Type: NONE] [Scalar: 1]
                { Stmt_for_inc[i0] -> MemRef_conv2[] };
    }


(The cast to float is there because otherwise LLVM would just compute
the constant result)
The interesting information for you would be the Domain {
Stmt_for_inc[i0] : i0 <= 999 and i0 >= 0 } of the loop body
(Stmt_for_inc). The loop body content itself is not printed here.

Michael