[Bug tree-optimization/106900] New: Regression after memchr optimization

[jbglaw@lug-owl.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106900

            Bug ID: 106900
           Summary: Regression after memchr optimization
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jbglaw@lug-owl.de
  Target Milestone: ---

Hi!

The optimization prepared in PR103798 ("memchr with a (small) constant string
should be expanded inline", c6cf555a88f8ffb8ec85c2b94fe656ab217260ea) caused a
regression for avr-elf, pru-elf and rl78-elf:

.../gcc/configure --prefix=... --enable-werror-always --enable-languages=all
--disable-gcov --disable-shared --disable-threads --target=pru-elf 
--without-headers                                                               
[...]                                                                           
make V=1 all-gcc                                                                
[...]                                                                           
/usr/lib/gcc-snapshot/bin/g++  -fno-PIE -c   -g -O2   -DIN_GCC 
-DCROSS_DIRECTORY_STRUCTURE   -fno-exceptions -fno-rtti
-fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings -W
cast-qual -Wmissing-format-attribute -Woverloaded-virtual -pedantic
-Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Werror -fno-common
 -DHAVE_CONFIG_H -I. -I. -I../../gcc/gcc -I../../gcc/gcc/.
-I../../gcc/gcc/../include -I../../gcc/gcc/../libcpp/include
-I../../gcc/gcc/../libcody  -I../../gcc/gcc/../libdecnumber
-I../../gcc/gcc/../libdecnumber/dpd -I../libdecnumber
-I../../gcc/gcc/../libbacktrace   -o tree-ssa-forwprop.o -MT
tree-ssa-forwprop.o -MMD -MP -MF ./.deps/tree-ssa-forwprop.TPo
../../gcc/gcc/tree-ssa-forwprop.cc
../../gcc/gcc/tree-ssa-forwprop.cc: In function 'bool
simplify_builtin_call(gimple_stmt_iterator*, tree)':
../../gcc/gcc/tree-ssa-forwprop.cc:1258:42: error: array subscript 1 is outside
array bounds of 'tree_node* [1]' [-Werror=array-bounds]
 1258 |             op[i - 1] = fold_convert_loc (loc, boolean_type_node,
      |                         ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
 1259 |                                           fold_build2_loc (loc,
      |                                           ~~~~~~~~~~~~~~~~~~~~~
 1260 |                                                           
BIT_IOR_EXPR,
      |                                                           
~~~~~~~~~~~~~
 1261 |                                                           
boolean_type_node,
      |                                                           
~~~~~~~~~~~~~~~~~~
 1262 |                                                            op[i - 1],
      |                                                            ~~~~~~~~~~
 1263 |                                                            op[i]));
      |                                                            ~~~~~~~
In file included from ../../gcc/gcc/system.h:707,
                 from ../../gcc/gcc/tree-ssa-forwprop.cc:21:
../../gcc/gcc/../include/libiberty.h:733:36: note: at offset 8 into object of
size [0, 8] allocated by '__builtin_alloca'
  733 | # define alloca(x) __builtin_alloca(x)
      |                    ~~~~~~~~~~~~~~~~^~~
../../gcc/gcc/../include/libiberty.h:365:40: note: in expansion of macro
'alloca'
  365 | #define XALLOCAVEC(T, N)        ((T *) alloca (sizeof (T) * (N)))
      |                                        ^~~~~~
../../gcc/gcc/tree-ssa-forwprop.cc:1250:22: note: in expansion of macro
'XALLOCAVEC'
 1250 |           tree *op = XALLOCAVEC (tree, isize);
      |                      ^~~~~~~~~~
cc1plus: all warnings being treated as errors
make[1]: *** [Makefile:1146: tree-ssa-forwprop.o] Error 1


(Last confirmed at c2c3e4f6698925c8c969d8525677fbfe98f78909.)