| Message ID | CAAgBjM==xR+5sHG5appwJdwJBFzNcBN76HF4idWnOm8t8u8gRA@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
On Sat, 25 Feb 2017, Prathamesh Kulkarni wrote: > Hi, > The attached patch deletes calls to strdup, strndup if it's > return-value is unused, > and same for realloc if the first arg is NULL. > Bootstrap+tested on x86_64-unknown-linux-gnu. > OK for GCC 8 ? Instead of specializing realloc(0,*) wherever we can perform the same optimization as with malloc, wouldn't it be better to optimize: realloc(0,n) -> malloc(n) and let the malloc optimizations happen? (realloc(p,0)->free(p) is more tricky because of the return value, like malloc(0))
On 2/25/17 2:40 AM, Prathamesh Kulkarni wrote: > The attached patch deletes calls to strdup, strndup if it's > return-value is unused, > and same for realloc if the first arg is NULL. Why limit ourselves to strdup and strndup? Can't we do the same for all functions that are marked as const/pure since we know they have no side effects other than their return value? Peter
On 2/28/17 12:49 PM, Peter Bergner wrote: > On 2/25/17 2:40 AM, Prathamesh Kulkarni wrote: >> The attached patch deletes calls to strdup, strndup if it's >> return-value is unused, >> and same for realloc if the first arg is NULL. > > Why limit ourselves to strdup and strndup? Can't we do the same > for all functions that are marked as const/pure since we know > they have no side effects other than their return value? Nevermind. Marc reminded me in the PR that these are not const/pure functions. Peter
On 02/25/2017 01:40 AM, Prathamesh Kulkarni wrote: > Hi, > The attached patch deletes calls to strdup, strndup if it's > return-value is unused, > and same for realloc if the first arg is NULL. > Bootstrap+tested on x86_64-unknown-linux-gnu. > OK for GCC 8 ? > > Thanks, > Prathamesh > > > pr79697-1.txt > > > 2017-02-25 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. > > testsuite/ > * gcc.dg/tree-ssa/pr79697.c: New test. OK for the trunk. jeff
On 25 April 2017 at 02:41, Jeff Law <law@redhat.com> wrote: > On 02/25/2017 01:40 AM, Prathamesh Kulkarni wrote: >> >> Hi, >> The attached patch deletes calls to strdup, strndup if it's >> return-value is unused, >> and same for realloc if the first arg is NULL. >> Bootstrap+tested on x86_64-unknown-linux-gnu. >> OK for GCC 8 ? >> >> Thanks, >> Prathamesh >> >> >> pr79697-1.txt >> >> >> 2017-02-25 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. >> >> testsuite/ >> * gcc.dg/tree-ssa/pr79697.c: New test. > > OK for the trunk. Hi Jeff, Did you intend to approve the original patch (pr79697-1.txt) or the latest one (pr79697-3.txt that also folds realloc (0, n) to malloc (n)) ? Thanks, Prathamesh > > jeff >
On 04/25/2017 12:06 AM, Prathamesh Kulkarni wrote: > On 25 April 2017 at 02:41, Jeff Law <law@redhat.com> wrote: >> On 02/25/2017 01:40 AM, Prathamesh Kulkarni wrote: >>> >>> Hi, >>> The attached patch deletes calls to strdup, strndup if it's >>> return-value is unused, >>> and same for realloc if the first arg is NULL. >>> Bootstrap+tested on x86_64-unknown-linux-gnu. >>> OK for GCC 8 ? >>> >>> Thanks, >>> Prathamesh >>> >>> >>> pr79697-1.txt >>> >>> >>> 2017-02-25 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. >>> >>> testsuite/ >>> * gcc.dg/tree-ssa/pr79697.c: New test. >> >> OK for the trunk. > Hi Jeff, > Did you intend to approve the original patch (pr79697-1.txt) or the > latest one (pr79697-3.txt that also folds realloc (0, n) to malloc > (n)) ? I was referring to the 3rd iteration. Sorry to have replied to the first patch in the series -- my patches queue is a bit of a mess as we're just getting started on gcc-8 stuff. jeff
On 29 April 2017 at 01:37, Jeff Law <law@redhat.com> wrote: > On 04/25/2017 12:06 AM, Prathamesh Kulkarni wrote: >> >> On 25 April 2017 at 02:41, Jeff Law <law@redhat.com> wrote: >>> >>> On 02/25/2017 01:40 AM, Prathamesh Kulkarni wrote: >>>> >>>> >>>> Hi, >>>> The attached patch deletes calls to strdup, strndup if it's >>>> return-value is unused, >>>> and same for realloc if the first arg is NULL. >>>> Bootstrap+tested on x86_64-unknown-linux-gnu. >>>> OK for GCC 8 ? >>>> >>>> Thanks, >>>> Prathamesh >>>> >>>> >>>> pr79697-1.txt >>>> >>>> >>>> 2017-02-25 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. >>>> >>>> testsuite/ >>>> * gcc.dg/tree-ssa/pr79697.c: New test. >>> >>> >>> OK for the trunk. >> >> Hi Jeff, >> Did you intend to approve the original patch (pr79697-1.txt) or the >> latest one (pr79697-3.txt that also folds realloc (0, n) to malloc >> (n)) ? > > I was referring to the 3rd iteration. Sorry to have replied to the first > patch in the series -- my patches queue is a bit of a mess as we're just > getting started on gcc-8 stuff. Committed as r247407, thanks! > > > jeff >
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr79697.c b/gcc/testsuite/gcc.dg/tree-ssa/pr79697.c new file mode 100644 index 0000000..a6e75a6 --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr79697.c @@ -0,0 +1,21 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-cddce-details" } */ + +void f(void) +{ + __builtin_strdup ("abc"); +} + +void g(void) +{ + __builtin_strndup ("abc", 3); +} + +void h(void) +{ + __builtin_realloc (0, 10); +} + +/* { dg-final { scan-tree-dump "Deleting : __builtin_strdup" "cddce1" } } */ +/* { dg-final { scan-tree-dump "Deleting : __builtin_strndup" "cddce1" } } */ +/* { dg-final { scan-tree-dump "Deleting : __builtin_realloc" "cddce1" } } */ diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c index 5ebe57b..b0f62b0 100644 --- a/gcc/tree-ssa-dce.c +++ b/gcc/tree-ssa-dce.c @@ -233,8 +233,17 @@ mark_stmt_if_obviously_necessary (gimple *stmt, bool aggressive) case BUILT_IN_CALLOC: case BUILT_IN_ALLOCA: case BUILT_IN_ALLOCA_WITH_ALIGN: + case BUILT_IN_STRDUP: + case BUILT_IN_STRNDUP: return; + case BUILT_IN_REALLOC: + { + tree arg0 = gimple_call_arg (stmt, 0); + if (operand_equal_p (arg0, null_pointer_node, 0)) + return; + break; + } default:; } /* Most, but not all function calls are required. Function calls that