From 298a4694f89ecb512be8ecba0512558996961fae Mon Sep 17 00:00:00 2001 From: Jan Hubicka Date: Sun, 21 Nov 2021 00:35:22 +0100 Subject: [PATCH] Fix looping flag discovery in ipa-pure-const The testcase shows situation where there is non-trivial cycle in the callgraph involving a noreturn call. This cycle is important for const function discovery but not important for pure. IPA pure const uses same strongly connected components for both propagations which makes it to get suboptimal result (does not detect the pure flag). However local pure const gets the situation right becaue it processes functions in right order. This hits rarely executed code in propagate_pure_const that merge results with previously known state that has long standing bug in it that makes it to throw away the looping flag. Bootstrapped/regtested x86_64-linux. gcc/ChangeLog: 2021-11-21 Jan Hubicka PR ipa/103052 * ipa-pure-const.c (propagate_pure_const): Fix merging of loping flag. gcc/testsuite/ChangeLog: 2021-11-21 Jan Hubicka PR ipa/103052 * gcc.c-torture/execute/pr103052.c: New test. (cherry picked from commit a0e99d5bb741d3db74a67d492f47b28217fbf88a) --- gcc/ipa-pure-const.c | 4 +-- .../gcc.c-torture/execute/pr103052.c | 35 +++++++++++++++++++ 2 files changed, 37 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr103052.c diff --git a/gcc/ipa-pure-const.c b/gcc/ipa-pure-const.c index 564c6629c92e..890826aea4c8 100644 --- a/gcc/ipa-pure-const.c +++ b/gcc/ipa-pure-const.c @@ -1665,9 +1665,9 @@ propagate_pure_const (void) if (w_l->state_previously_known != IPA_NEITHER && this_state > w_l->state_previously_known) { - this_state = w_l->state_previously_known; if (this_state == IPA_NEITHER) - this_looping = w_l->looping_previously_known; + this_looping = w_l->looping_previously_known; + this_state = w_l->state_previously_known; } if (!this_looping && self_recursive_p (w)) this_looping = true; diff --git a/gcc/testsuite/gcc.c-torture/execute/pr103052.c b/gcc/testsuite/gcc.c-torture/execute/pr103052.c new file mode 100644 index 000000000000..bef8674a43c7 --- /dev/null +++ b/gcc/testsuite/gcc.c-torture/execute/pr103052.c @@ -0,0 +1,35 @@ +static void js_error(void); +static int top; +static void js_throw(void) +{ + __builtin_exit(0); +} + +// LOCATION A -- if js_pop is here, the bug is present +static void js_pop(void) +{ + if (++top > 100) + js_error(); +} + +static void jsC_error(const char *v) +{ + if (v[0] == 0) + js_error(); + js_throw(); +} +static void checkfutureword(const char *exp) +{ + if (!__builtin_strcmp(exp, "const")) + jsC_error("boom"); +} +static void js_error(void) { + checkfutureword("foo"); + checkfutureword("bar"); + js_pop(); +} +int main(void) +{ + checkfutureword("const"); + __builtin_abort (); +} -- 2.43.5