> Hi, > this is updated patch which adds -fmalloc-dce flag to control malloc/free > removal. I ended up copying what -fallocation-dse does so -fmalloc-dce=1 > enables malloc/free removal provided return value is unused otherwise and > -fmalloc-dce=2 allows additional NULL pointer checks which it folds to > non-NULL > direction. > > I also added compensation for the gcc.dg/analyzer/pr101837.c testcase and > added testcase that std::nothrow variant of operator new is now optimized way. > > With the -fmalloc-dce=n I can also add a level which emits runtime check for > half > of address space and calloc overflow if it seems useful, but perhaps > incrementally. Adding size parameter tracking is not that hard (I posted WIP > patch for that). > > Bootstrapped/regtested x86_64-linux, OK? > > * common.opt: Add -fmalloc-dce. > * doc/invoke.texi: Document it; also add missing -flifetime-dse entry. > * tree-ssa-dce.cc (is_removable_allocation_p): Break out from > ... > (mark_stmt_if_obviously_necessary): ... here; also check that > operator new satisfies gimple_call_from_new_or_delete. > (checks_return_value_of_removable_allocation_p): New Function. > (mark_all_reaching_defs_necessary_1): add missing case ofr > STRDUP and STRNDUP > (propagate_necessity): Use is_removable_allocation_p and > checks_return_value_of_removable_allocation_p. > (eliminate_unnecessary_stmts): Update conditionals that use > removed allocation; use is_removable_allocation_p. > > gcc/testsuite/ChangeLog: > > * g++.dg/cdce3.C: Disable allocation dce. > * g++.dg/tree-ssa/pr19476-1.C: Likewise. > * g++.dg/tree-ssa/pr19476-2.C: Likewise. > * g++.dg/tree-ssa/pr19476-3.C: Likewise. > * g++.dg/tree-ssa/pr19476-4.C: Likewise. > * gcc.dg/analyzer/pr101837.c: Disable malloc dce. > * gcc.dg/tree-ssa/pr19831-3.c: Update. > * gfortran.dg/pr68078.f90: Disable malloc DCE. > * g++.dg/tree-ssa/dce-1.C: New test.
I would like to ping this, since I have some followup changes on DCE. thanks, Honza
