Re: [PATCH] Fix PR68067

[Richard Biener <rguenther at suse dot de>]

On Fri, 6 Nov 2015, Alan Lawrence wrote:

> On 28/10/15 13:38, Richard Biener wrote:
> > 
> > Applied as follows.
> > 
> > Bootstrapped / tested on x86_64-unknown-linux-gnu.
> > 
> > Richard.
> > 
> > 2015-10-28  Richard Biener  <rguenther@suse.de>
> > 
> > 	* fold-const.c (negate_expr_p): Adjust the division case to
> > 	properly avoid introducing undefined overflow.
> > 	(fold_negate_expr): Likewise.
> 
> Since this we've been seeing an ICE compiling polynom.c from 254.gap in
> SPEC2000 on aarch64-linux-gnu with -O3 -ffast-math -mcpu=cortex-a53 (or -Ofast
> -mcpu=cortex-a53), on both native (bootstrapped and --disable-bootstrap) and
> cross-linux builds.
> 
> A number of options prevent the ICE, e.g. any of -fno-thread-jumps,
> -fno-strict-overflow, -fdump-tree-alias or -fdump-tree-ealias (!). Similarly,
> dropping the -mcpu=cortex-a53, or changing to -mcpu=cortex-a57.
> 
> (I have a recent build in a chroot for which -fno-strict-overflow does *not*
> fix the ICE but haven't yet figured out exactly what the difference in the
> chroot environment is.)
> 
> Moreover, preprocessing in a separate step (i.e. piping preprocessed output
> via a file with -E), also avoids the ICE. (This is hindering my efforts to
> reduce the testcase!).  So my hypothesis is that this is a
> front-end/preprocessor bug, rather than anything directly due to this commit.
> 
> The error message in full (line refs from that commit, r229479) is:
> =====
> ../spec2000/benchspec/CINT2000/254.gap/src/polynom.c: In function
> ‘NormalizeCoeffsListx’:
> ../spec2000/benchspec/CINT2000/254.gap/src/polynom.c:358:11: error:
> incompatible types in PHI argument 0
>  TypHandle NormalizeCoeffsListx ( hdC )
>            ^
> long int
> 
> int
> 
> ../spec2000/benchspec/CINT2000/254.gap/src/polynom.c:358:11: error: location
> references block not in block tree
> l1_279 = PHI <1(28), l1_299(33)>

^^^

this is the error to look at!  It means that the GC heap will be corrupted
quite easily.

> ../spec2000/benchspec/CINT2000/254.gap/src/polynom.c:358:11: error: invalid
> PHI argument

which means this could be a followup error.  We do have a bugreport (or 
two) about similar issues that were tracked down to different patches.

Somebody needs to sit down and debug this properly ;)

> ../spec2000/benchspec/CINT2000/254.gap/src/polynom.c:358:11: internal compiler
> error: tree check: expected class ‘type’, have ‘declaration’ (namespace_decl)
> in useless_type_conversion_p, at gimple-expr.c:84
> 0xd110ef tree_class_check_failed(tree_node const*, tree_code_class, char
> const*, int, char const*)
>         ../../gcc-fsf/gcc/tree.c:9643
> 0x82561b tree_class_check
>         ../../gcc-fsf/gcc/tree.h:3042
> 0x82561b useless_type_conversion_p(tree_node*, tree_node*)
>         ../../gcc-fsf/gcc/gimple-expr.c:84
> 0xaca043 verify_gimple_phi
>         ../../gcc-fsf/gcc/tree-cfg.c:4673
> 0xaca043 verify_gimple_in_cfg(function*, bool)
>         ../../gcc-fsf/gcc/tree-cfg.c:4967
> 0x9c2e0b execute_function_todo
>         ../../gcc-fsf/gcc/passes.c:1967

Interesting would be for which pass this happens - just print
*pass at this point.

> 0x9c360b do_per_function
>         ../../gcc-fsf/gcc/passes.c:1659
> 0x9c3807 execute_todo
>         ../../gcc-fsf/gcc/passes.c:2022
> Please submit a full bug report,
> with preprocessed source if appropriate.
> =====
> which looks like an "incompatible types from PHI argument" from a first call
> to verify_gimple_phi, then a second call to verify_gimple_phi prints "invalid
> phi argument" and ICEs in the test just before possibly printing a second
> incompatible_types message.
> 
> 
> --Alan
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)