[llvm-dev] Which optimization pass deals with heap values?

[chuanqi.xcq via llvm-dev]

Hi,

   The optimization should be done at InstructionCombine pass. See: https://godbolt.org/z/zGvrMerKv. Previous cleaning passes are necessary.

   But I feel this optimization is a little bit aggresive. Since it changes the behavior of the program. The program above might hit a memory leak while the optimized one would not.

   As a reference, GCC wouldn't do this under O2: https://godbolt.org/z/5z1GWMWPj. It would only do this under O3.

Thanks,
Chuanqi
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From:llvm-dev <llvm-dev at lists.llvm.org>
Send Time:2022年1月17日(星期一) 16:08
To:llvm-dev <llvm-dev at lists.llvm.org>
Subject:[llvm-dev] Which optimization pass deals with heap values?

All the optimization passes I can find in the documentation, deal with register, stack or global values; I cannot find any mention of anything trying to optimize values on the heap. But this:

#include <stdlib.h>

int main(int argc, char **argv) {
  int *a = malloc(10 * sizeof(int));
  for (int i = 0; i < 10; i++)
    a[i] = i;
  return a[5];
}

compiles to 'ret 5' (as it should). Which pass does that?

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