[Bug tree-optimization/79697] unused realloc(0, n) not eliminated

[prathamesh3492 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79697

--- Comment #8 from prathamesh3492 at gcc dot gnu.org ---
Author: prathamesh3492
Date: Sat Apr 29 10:05:13 2017
New Revision: 247407

URL: https://gcc.gnu.org/viewcvs?rev=247407&root=gcc&view=rev
Log:
2017-04-29  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>

        PR tree-optimization/79697
        * tree-ssa-dce.c (mark_stmt_if_obviously_necessary): Check if callee
        is BUILT_IN_STRDUP, BUILT_IN_STRNDUP, BUILT_IN_REALLOC.
        (propagate_necessity): Check if def_callee is BUILT_IN_STRDUP or
        BUILT_IN_STRNDUP.
        * gimple-fold.c (gimple_fold_builtin_realloc): New function.
        (gimple_fold_builtin): Call gimple_fold_builtin_realloc.

testsuite/
        * gcc.dg/tree-ssa/pr79697.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/pr79697.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/gimple-fold.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-dce.c