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From: "david.bolvansky at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/95492] New: Avoid recursive inlining for -O2
Date: Wed, 03 Jun 2020 07:23:19 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95492

            Bug ID: 95492
           Summary: Avoid recursive inlining for -O2
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: david.bolvansky at gmail dot com
  Target Milestone: ---

Test case from PR90949:

int puts(const char*);
void free(void*);
void* malloc(unsigned long);
#define NULL 0

struct Node
{
    struct Node* child;
};

void walk(struct Node* module, int cleanup)
{
    if (module =3D=3D NULL) {
        return;
    }
    if (!cleanup) {
        puts("No cleanup");
    }
    walk(module->child, cleanup);
    if (cleanup) {
        free(module);
    }
}

int main()
{
    struct Node* node =3D malloc(sizeof(struct Node));
    node->child =3D NULL;
    walk(node, 1);
}

https://godbolt.org/z/aqVApt


Since GCC 10, GCC inlines recursion with -O2/-O3. With -O3, new bigger code=
 is
justified, but for -O2, it is quite questionable whether GCC should inline =
it
or not (or possibly, less agressive "inlining" for -O2)=