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From: "slyfox at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/107661] [13 Regression] lambdas get merged
 incorrectly in tempaltes, cause llvm-12 miscompilation since
 r13-3358-ge0403e95689af7
Date: Fri, 18 Nov 2022 08:54:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107661

--- Comment #10 from Sergei Trofimovich <slyfox at gcc dot gnu.org> ---
I think ipa-cp adds the call edge info in wrong direction. a.cc.081i.cp sni=
ppet
around do3() param1 (our callback):

  IPA lattices after all propagation:

  Lattices:
    ...
    Node: void do3(volatile int*, function_ref)/25:
      ...
      param [1]: VARIABLE
           ctxs: VARIABLE
           Bits unusable (BOTTOM)
           [irange] int VARYING
          offset 0: callback_fn_L [scc: 3, from: 25(0.330000) 26(1.000000)]
[loc_time: 17, loc_size: 13, prop_time: 17, prop_size: 13]
                    callback_fn_R [scc: 4, from: 25(0.330000) 26(1.000000)]
[loc_time: 9, loc_size: 13, prop_time: 9, prop_size: 13]

  ...
  Evaluating opportunities for void do3(volatile int*, function_ref)/25.
   - considering value callback_fn_L for param #1 Expired, offset: 0
(caller_count: 2)
       good_cloning_opportunity_p (time: 17, size: 13, freq_sum: 1.33,
self_scc) -> evaluation: 1739.23, threshold: 500
    Creating a specialized node of void do3(volatile int*, function_ref)/25.
       the new node is void do3.constprop(volatile int*, function_ref)/33.
       Aggregate replacements: 1[0]=3Dcallback_fn_L
  ipa-prop: Discovered an indirect call to a known target (void
do3.constprop(volatile int*, function_ref)/33 -> void callback_fn_L()/15), =
for
stmt _1 ();
    ../a.cc:37:19: optimized: converting indirect call in void
do3.constprop(volatile int*, function_ref)/33 to direct call to void
callback_fn_L()/15

    Evaluating opportunities for void do3(volatile int*, function_ref)/25.
     - adding an extra caller void do3(volatile int*, function_ref)/25 of v=
oid
do3.constprop(volatile int*, function_ref)/33

Note: the uncloned do3() is a self-recursive function. I would expect cloned
do3.constprop() to refer to uncloned do3().
If I read "adding an extra caller" correctly it adds an edge in wrong
direction: do3() now calls do3.constptop().=