Hello everyone,
would it be possible to extend gfortran attribute support to handle
NOINLINE too? Like: "!GCC$ ATTRIBUTES noinline :: ...".
Recent testing with gcc-13 trunk uncovered several issues with LTO
usage and for now it is unknown if it is host specific or something
else. Given that there is little to no control from the fortran side
to influence how lto1 backend handles symbol manipulations, such
attribute (while not fixing root problems) would allow workaround
compilation issues at source level, since most of LTO usage problems
come from inlining and limits of resources available.
While there, it would be handy to have support for NORETURN and WEAK
attributes too.
In one of the projects just adding 2 NORETURN comment pragmas into
commonly used custom critical abort subroutine interfaces reduced the
number of -Wmaybe-uninitialized diagnostics from 2867 to 2654. That
is a huge reduction of pure false positives and results in smaller
binaries produced.
Explaining the need for the WEAK attribute is somewhat more
complicated, when it is needed - it is needed (even if that means
compiling to assembly intermediates and sed "/SYM/s/.globl/.weak/"
which is quite fragile).
Attached is a proof of concept patch with some test cases adapted
mainly from already existing C testsuite variants and tested on
x86_64. These additions are not intrusive and quite useful.
I'm willing to help test/code to get NOINLINE support added,
Best regards,
Rimvydas
From 7a197623c2efb30e4ecf78ce650b6727eef5e60b Mon Sep 17 00:00:00 2001
From: Rimvydas Jasinskas <rimvydas....@gmail.com>
Date: Fri, 10 Feb 2023 04:34:12 +0000
Subject: Fortran: Add !GCC$ attributes NOINLINE,NORETURN,WEAK
gcc/fortran/ChangeLog:
* decl.cc: Add EXT_ATTR_NOINLINE, EXT_ATTR_NORETURN, EXT_ATTR_WEAK.
* gfortran.h (ext_attr_id_t): Ditto.
* gfortran.texi (GCC$ ATTRIBUTES): Document them.
* trans-decl.cc (build_function_decl): Apply them.
gcc/testsuite/ChangeLog:
* gfortran.dg/noinline.f90: New test.
* gfortran.dg/noreturn-1.f90: New test.
* gfortran.dg/noreturn-2.f90: New test.
* gfortran.dg/noreturn-3.f90: New test.
* gfortran.dg/noreturn-4.f90: New test.
* gfortran.dg/noreturn-5.f90: New test.
* gfortran.dg/weak-1.f90: New test.
Signed-off-by: Rimvydas Jasinskas <rimvydas....@gmail.com>
---
gcc/fortran/decl.cc | 3 ++
gcc/fortran/gfortran.h | 3 ++
gcc/fortran/gfortran.texi | 9 +++++
gcc/fortran/trans-decl.cc | 19 +++++++++-
gcc/testsuite/gfortran.dg/noinline.f90 | 23 ++++++++++++
gcc/testsuite/gfortran.dg/noreturn-1.f90 | 62 ++++++++++++++++++++++++++++++++
gcc/testsuite/gfortran.dg/noreturn-2.f90 | 53 +++++++++++++++++++++++++++
gcc/testsuite/gfortran.dg/noreturn-3.f90 | 14 ++++++++
gcc/testsuite/gfortran.dg/noreturn-4.f90 | 11 ++++++
gcc/testsuite/gfortran.dg/noreturn-5.f90 | 9 +++++
gcc/testsuite/gfortran.dg/weak-1.f90 | 6 ++++
11 files changed, 211 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gfortran.dg/noinline.f90
create mode 100644 gcc/testsuite/gfortran.dg/noreturn-1.f90
create mode 100644 gcc/testsuite/gfortran.dg/noreturn-2.f90
create mode 100644 gcc/testsuite/gfortran.dg/noreturn-3.f90
create mode 100644 gcc/testsuite/gfortran.dg/noreturn-4.f90
create mode 100644 gcc/testsuite/gfortran.dg/noreturn-5.f90
create mode 100644 gcc/testsuite/gfortran.dg/weak-1.f90
diff --git a/gcc/fortran/decl.cc b/gcc/fortran/decl.cc
index 27b728ff551..eec0314cf4c 100644
--- a/gcc/fortran/decl.cc
+++ b/gcc/fortran/decl.cc
@@ -11732,6 +11732,9 @@ const ext_attr_t ext_attr_list[] = {
{ "fastcall", EXT_ATTR_FASTCALL, "fastcall" },
{ "no_arg_check", EXT_ATTR_NO_ARG_CHECK, NULL },
{ "deprecated", EXT_ATTR_DEPRECATED, NULL },
+ { "noinline", EXT_ATTR_NOINLINE, NULL },
+ { "noreturn", EXT_ATTR_NORETURN, NULL },
+ { "weak", EXT_ATTR_WEAK, NULL },
{ NULL, EXT_ATTR_LAST, NULL }
};
diff --git a/gcc/fortran/gfortran.h b/gcc/fortran/gfortran.h
index 9884a55882b..a893ee06f3d 100644
--- a/gcc/fortran/gfortran.h
+++ b/gcc/fortran/gfortran.h
@@ -838,6 +838,9 @@ typedef enum
EXT_ATTR_FASTCALL,
EXT_ATTR_NO_ARG_CHECK,
EXT_ATTR_DEPRECATED,
+ EXT_ATTR_NOINLINE,
+ EXT_ATTR_NORETURN,
+ EXT_ATTR_WEAK,
EXT_ATTR_LAST, EXT_ATTR_NUM = EXT_ATTR_LAST
}
ext_attr_id_t;
diff --git a/gcc/fortran/gfortran.texi b/gcc/fortran/gfortran.texi
index c3813d06c20..4d7f4dbd7d8 100644
--- a/gcc/fortran/gfortran.texi
+++ b/gcc/fortran/gfortran.texi
@@ -3246,6 +3246,15 @@ requires an explicit interface.
@item @code{DEPRECATED} -- print a warning when using a such-tagged
deprecated procedure, variable or parameter; the warning can be suppressed
with @option{-Wno-deprecated-declarations}.
+@item @code{NOINLINE} -- prevent inlining given function.
+@item @code{NORETURN} -- add hint that given function cannot return. This
+makes slightly better code. More importantly, it helps avoid spurious warnings
+of uninitialized variables.
+@item @code{WEAK} -- emit the declaration of an external symbol as a weak
+symbol rather than a global. This is primarily useful in defining library
+functions that can be overridden in user code, though it can also be used with
+non-function declarations. The overriding symbol must have the same type as
+the weak symbol.
@end itemize
diff --git a/gcc/fortran/trans-decl.cc b/gcc/fortran/trans-decl.cc
index f7a7ff607cd..6799d87158f 100644
--- a/gcc/fortran/trans-decl.cc
+++ b/gcc/fortran/trans-decl.cc
@@ -2338,7 +2338,7 @@ module_sym:
}
/* Mark non-returning functions. */
- if (sym->attr.noreturn)
+ if (sym->attr.noreturn || sym->attr.ext_attr & (1 << EXT_ATTR_NORETURN))
TREE_THIS_VOLATILE(fndecl) = 1;
sym->backend_decl = fndecl;
@@ -2482,6 +2482,23 @@ build_function_decl (gfc_symbol * sym, bool global)
TREE_SIDE_EFFECTS (fndecl) = 0;
}
+ /* Mark noinline functions. */
+ if (attr.ext_attr & (1 << EXT_ATTR_NOINLINE))
+ DECL_UNINLINABLE (fndecl) = 1;
+
+ /* Mark noreturn functions. */
+ if (attr.ext_attr & (1 << EXT_ATTR_NORETURN))
+ TREE_THIS_VOLATILE (fndecl) = 1;
+
+ /* Mark weak functions. */
+ if (attr.ext_attr & (1 << EXT_ATTR_WEAK))
+ {
+ if (SUPPORTS_WEAK)
+ declare_weak (fndecl);
+ else
+ gfc_fatal_error ("weak declarations not supported on this target");
+
+ }
/* Layout the function declaration and put it in the binding level
of the current function. */
diff --git a/gcc/testsuite/gfortran.dg/noinline.f90 b/gcc/testsuite/gfortran.dg/noinline.f90
new file mode 100644
index 00000000000..edae72ea5eb
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/noinline.f90
@@ -0,0 +1,23 @@
+! { dg-do compile }
+! { dg-options "-O2 -fdump-tree-dom2" }
+
+subroutine bar(n,m,p,s)
+implicit none
+integer :: n,m
+real,intent(inout) :: p(n),s(*)
+call foo(n,m,p,s)
+call foo(n,m,p,s)
+end subroutine bar
+
+subroutine foo(n,m,p,b)
+implicit none
+integer :: n,m,j
+real,intent(inout) :: p(n),b(*)
+!GCC$ ATTRIBUTES noinline :: foo
+do j=1,n
+ b(m+j-1)=p(j)
+enddo
+m=m+n
+end subroutine foo
+
+! { dg-final { scan-tree-dump-times "foo \\(" 4 "dom2"} }
diff --git a/gcc/testsuite/gfortran.dg/noreturn-1.f90 b/gcc/testsuite/gfortran.dg/noreturn-1.f90
new file mode 100644
index 00000000000..3155cdf22aa
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/noreturn-1.f90
@@ -0,0 +1,62 @@
+! Check for various valid and erroneous "noreturn" cases.
+! { dg-do compile }
+! { dg-options "-O2" }
+
+module barbar
+!GCC$ ATTRIBUTES noreturn :: bar1
+contains
+subroutine bar1
+end subroutine bar1 ! { dg-warning "'noreturn' function does return" "detect falling off end of noreturn" }
+end module
+
+subroutine foo1
+!GCC$ ATTRIBUTES noreturn :: foo1
+end subroutine foo1 ! { dg-warning "'noreturn' function does return" "detect falling off end of noreturn" }
+
+subroutine foo2
+!GCC$ ATTRIBUTES noreturn :: foo2
+call exit(0)
+end subroutine foo2 ! { dg-bogus "warning:" "this function should not get any warnings" }
+
+subroutine foo3
+end subroutine foo3 ! { dg-bogus "warning:" "this function should not get any warnings" }
+
+subroutine foo4
+!GCC$ ATTRIBUTES noreturn :: foo4
+call foo2()
+end subroutine foo4 ! { dg-bogus "warning:" "this function should not get any warnings" }
+
+subroutine foo5
+!GCC$ ATTRIBUTES noreturn :: foo5
+return ! { dg-warning "'noreturn' function does return" "detect invalid return" }
+end subroutine foo5
+
+subroutine foo6
+return
+end subroutine foo6 ! { dg-bogus "warning:" "this function should not get any warnings" }
+
+subroutine foo7
+call foo6()
+end subroutine foo7 ! { dg-bogus "warning:" "this function should not get any warnings" }
+
+subroutine foo8
+!GCC$ ATTRIBUTES noreturn :: foo8
+call foo7()
+end subroutine foo8 ! { dg-warning "'noreturn' function does return" "detect return from tail call" }
+
+subroutine foo9
+!GCC$ ATTRIBUTES noreturn :: foo9
+interface
+subroutine bar
+!GCC$ ATTRIBUTES noreturn :: bar
+end subroutine bar
+end interface
+call bar()
+end subroutine foo9 ! { dg-bogus "warning:" "this function should not get any warnings" }
+
+function ffo1()
+implicit none
+!GCC$ ATTRIBUTES noreturn :: ffo1
+integer :: ffo1
+ffo1 = 0
+end function ffo1 ! { dg-warning "'noreturn' function does return" "detect falling off end of noreturn" }
diff --git a/gcc/testsuite/gfortran.dg/noreturn-2.f90 b/gcc/testsuite/gfortran.dg/noreturn-2.f90
new file mode 100644
index 00000000000..1bb4793234f
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/noreturn-2.f90
@@ -0,0 +1,53 @@
+! { dg-do compile }
+! { dg-options "-O2 -Wuninitialized" }
+
+subroutine foo1
+implicit none
+interface
+subroutine bar1
+!GCC$ ATTRIBUTES noreturn :: bar1
+end subroutine
+end interface
+real,allocatable :: d(:) ! { dg-note "declared here" "note" }
+d = 0. ! { dg-warning "used uninitialized" "uninitialized descriptor" }
+call bar1()
+d = 0. ! { dg-bogus "warning:" "not optimized out" }
+end subroutine foo1
+
+function foo2()
+integer :: foo2
+interface
+subroutine bar2
+!GCC$ ATTRIBUTES noreturn :: bar2
+end subroutine
+end interface
+call bar2
+return ! { dg-bogus "__result_foo2' is used uninitialized" "return" }
+foo2 = 0
+end function foo2
+
+subroutine foo3
+implicit none
+integer :: i,j
+interface
+subroutine abort2
+!GCC$ ATTRIBUTES noreturn :: abort2
+end subroutine
+end interface
+call abort2()
+do i=1,j-1 ; end do ! { dg-bogus "is used uninitialized" "uninitialized" }
+end subroutine foo3
+
+function foo4()
+integer :: foo4
+!$GCC$ ATTRIBUTES noreturn :: foo4
+foo4 = 1
+end function
+
+subroutine foo5(k)
+implicit none
+integer :: i, k
+!GCC$ ATTRIBUTES noreturn :: mpi_abort
+call mpi_abort()
+k = i
+end subroutine
diff --git a/gcc/testsuite/gfortran.dg/noreturn-3.f90 b/gcc/testsuite/gfortran.dg/noreturn-3.f90
new file mode 100644
index 00000000000..fefa092aef0
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/noreturn-3.f90
@@ -0,0 +1,14 @@
+! { dg-do compile }
+! { dg-additional-options "-Wuninitialized -Wmaybe-uninitialized" }
+
+subroutine foo
+implicit none
+integer :: i
+!GCC$ ATTRIBUTES noreturn :: mpi_abort
+if (getpid() == 1) then
+ call mpi_abort()
+else
+ i = 8
+endif
+if (i > 0) print *, i
+end subroutine
diff --git a/gcc/testsuite/gfortran.dg/noreturn-4.f90 b/gcc/testsuite/gfortran.dg/noreturn-4.f90
new file mode 100644
index 00000000000..e4024e27ccc
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/noreturn-4.f90
@@ -0,0 +1,11 @@
+! { dg-do run { target { nonpic || pie_enabled } } }
+! { dg-options "-O2" }
+
+program bar
+call foo1()
+call noreturn_autodetection_failed() ! check if optimized out
+end program
+
+subroutine foo1
+stop 0
+end subroutine foo1
diff --git a/gcc/testsuite/gfortran.dg/noreturn-5.f90 b/gcc/testsuite/gfortran.dg/noreturn-5.f90
new file mode 100644
index 00000000000..d07b0502f08
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/noreturn-5.f90
@@ -0,0 +1,9 @@
+! { dg-do compile }
+! { dg-options "-O2" }
+
+subroutine bar
+!GCC$ ATTRIBUTES noreturn :: foo1
+call foo1()
+call noreturn_autodetection_failed()
+end subroutine
+! /* { dg-final { scan-assembler-not "noreturn_autodetection_failed" } } */
diff --git a/gcc/testsuite/gfortran.dg/weak-1.f90 b/gcc/testsuite/gfortran.dg/weak-1.f90
new file mode 100644
index 00000000000..d9aca686775
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/weak-1.f90
@@ -0,0 +1,6 @@
+! { dg-do compile }
+! { dg-require-weak "" }
+! { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?impl" } }
+subroutine impl
+!GCC$ ATTRIBUTES weak :: impl
+end subroutine
--
2.12.3
