[Bug tree-optimization/63445] [5 Regression] request: make -Wstrict-overflow avoid a class of false positives

["rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63445

--- Comment #5 from rguenther at suse dot de <rguenther at suse dot de> ---
On Tue, 7 Oct 2014, manu at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63445
> 
> --- Comment #4 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
> > i_15 could be negative and thus j_9 - i_15 could well overflow the input
> > range at the +INF side.  (i_15 is [-INF, j_5(D) + -1])
> 
> Actually, this is a very good point. There is indeed a potential integer
> overflow in the original code. Thus, the warning seems valid.
> 
> Perhaps the warning message could say that the problem is that "j - i" can
> overflow if i is negative.

Sure - but we warn about the comparison against zero which doesn't
behave differently if overflow wraps or is undefined.
>From gcc-bugs-return-463448-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Tue Oct 07 14:09:47 2014
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From: "mliska at suse dot cz" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug ipa/63470] New: [5 Regression] lto1: internal compiler error: in estimate_edge_growth, at ipa-inline.h:308
Date: Tue, 07 Oct 2014 14:09:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idc470

            Bug ID: 63470
           Summary: [5 Regression] lto1: internal compiler error: in
                    estimate_edge_growth, at ipa-inline.h:308
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mliska at suse dot cz
                CC: hubicka at ucw dot cz

Starting from r215794 Firefox produces following error in WPA with -flto and
--enable-checking=all:

lto1: internal compiler error: in estimate_edge_growth, at ipa-inline.h:308
0x7d7fc1 estimate_edge_growth
    ../../gcc/ipa-inline.h:307
0x7d7fc1 estimate_size_after_inlining(cgraph_node*, cgraph_edge*)
    ../../gcc/ipa-inline-analysis.c:3817
0xf388d1 caller_growth_limits
    ../../gcc/ipa-inline.c:186
0xf388d1 can_inline_edge_p
    ../../gcc/ipa-inline.c:363
0xf3acdd update_callee_keys
    ../../gcc/ipa-inline.c:1236
0xf3c9a6 inline_small_functions
    ../../gcc/ipa-inline.c:1818
0xf3c9a6 ipa_inline
    ../../gcc/ipa-inline.c:2182
0xf3c9a6 execute
    ../../gcc/ipa-inline.c:2542

Edge:
caller:
_ZNK12SkRefCntBase16internal_disposeEv/14636955 (internal_dispose)
@0x7f9c1a33d178
  Type: function definition analyzed
  Visibility: virtual
  next sharing asm name: 14636951
  References:
  Referring:
  Read from file:
/home/marxin/Programming/gecko-dev/obj-x86_64-unknown-linux-gnu/toolkit/library/build/../../../gfx/2d/Unified_cpp_gfx_2d0.o
  Function internal_dispose/14636955 is inline copy in __base_dtor /13594851
  Clone of _ZNK12SkRefCntBase16internal_disposeEv/14636951
  Availability: local
  First run: 0
  Function flags: local
  Called by: _ZNK12SkRefCntBase5unrefEv.part.40/14636954 (inlined)
(indirect_inlining) (0.02 per call)
  Calls: _ZN13SkGPipeCanvasD0Ev/13594853 (indirect_inlining) (0.01 per call)
callee:
_ZN13SkGPipeCanvasD0Ev/13594853 (__deleting_dtor ) @0x7f9c1575d8d0
  Type: function definition analyzed
  Visibility: prevailing_def_ironly virtual
  Address is taken.
  References:
  Referring: _ZTV13SkGPipeCanvas/13595722
(addr)_ZNK12SkRefCntBase16internal_disposeEv/14605659 (addr)
(speculative)_ZNK12SkRefCntBase16internal_disposeEv/14614102 (addr)
(speculative)_ZNK12SkRefCntBase16internal_disposeEv/14636951 (addr)
(speculative)
  Read from file:
/home/marxin/Programming/gecko-dev/obj-x86_64-unknown-linux-gnu/toolkit/library/build/../../../gfx/skia/Unified_cpp_gfx_skia20.o
  Availability: available
  First run: 0
  Function flags:
  Called by: _ZNK12SkRefCntBase16internal_disposeEv/14636955
(indirect_inlining) (0.01 per call)
_ZNK12SkRefCntBase16internal_disposeEv/14636951 (speculative)
(indirect_inlining) (0.03 per call)
_ZNK12SkRefCntBase16internal_disposeEv/14614102 (speculative)
(indirect_inlining) (0.08 per call)
_ZNK12SkRefCntBase16internal_disposeEv/14605659 (speculative)
(indirect_inlining) (0.08 per call)
  Calls: moz_free/1431 (1.00 per call) _ZN13SkGPipeCanvasD1Ev/13594852 (1.00
per call)

Thanks,
Martin