From 0d00e57d09d98d6ef11dc431be1ac2c927a6d3c5 Mon Sep 17 00:00:00 2001 From: Henri Menke Date: Fri, 29 May 2026 18:09:05 +0000 Subject: [PATCH v2] fortran: add INLINE and ALWAYS_INLINE attributes gfortran already understands the !GCC$ ATTRIBUTES NOINLINE directive to suppress inlining of a procedure, but there was no way to request the opposite. This adds two attributes: !GCC$ ATTRIBUTES inline :: my_procedure !GCC$ ATTRIBUTES always_inline :: my_procedure INLINE is a plain hint equivalent to the C inline keyword and only sets DECL_DECLARED_INLINE_P, so the inliner's size limits still apply. ALWAYS_INLINE corresponds to the C always_inline attribute and additionally sets DECL_DISREGARD_INLINE_LIMITS. Since Fortran has no inline keyword, DECL_DECLARED_INLINE_P is set explicitly. Setting only DECL_DISREGARD_INLINE_LIMITS would make the middle-end warn that the always-inline function might not be inlinable. INLINE and ALWAYS_INLINE are incompatible with NOINLINE. In the middle-end the DECL_UNINLINABLE flag set by NOINLINE always wins, so the inline request would be silently ignored. To avoid that surprise the directive parser warns and drops the inline attribute when both are applied to the same procedure, whether in one directive or in two. The new EXT_ATTR_* values are appended at the end of the enum because the symbol_attribute.ext_attr bitmask is written to module files. Appending preserves the existing bit positions and keeps modules written by older gfortran readable. Bootstrapped and regtested on x86_64-pc-linux-gnu with --enable-languages=c,c++,fortran. All three stages built and the stage 2 and 3 comparison succeeded. The gfortran testsuite shows no regressions (75660 expected passes, 339 expected failures, 0 unexpected failures) and the four new tests pass. gcc/fortran/ChangeLog: * gfortran.h (enum ext_attr_id_t): Add EXT_ATTR_INLINE and EXT_ATTR_ALWAYS_INLINE at the end. Document that new attributes must be appended to preserve module compatibility. * decl.cc (ext_attr_list): Add "inline" and "always_inline". (gfc_match_gcc_attributes): Warn about and drop INLINE or ALWAYS_INLINE when combined with NOINLINE on the same symbol. * trans-decl.cc (build_function_decl): Handle EXT_ATTR_INLINE and EXT_ATTR_ALWAYS_INLINE by setting DECL_DECLARED_INLINE_P, and DECL_DISREGARD_INLINE_LIMITS for ALWAYS_INLINE. * gfortran.texi (ATTRIBUTES directive): Document INLINE and ALWAYS_INLINE. gcc/testsuite/ChangeLog: * gfortran.dg/always_inline_1.f90: New test. * gfortran.dg/always_inline_2.f90: New test. * gfortran.dg/inline_1.f90: New test. * gfortran.dg/inline_2.f90: New test. Signed-off-by: Henri Menke --- gcc/fortran/decl.cc | 23 ++++++++++++++++ gcc/fortran/gfortran.h | 10 ++++++- gcc/fortran/gfortran.texi | 8 ++++++ gcc/fortran/trans-decl.cc | 10 +++++++ gcc/testsuite/gfortran.dg/always_inline_1.f90 | 26 ++++++++++++++++++ gcc/testsuite/gfortran.dg/always_inline_2.f90 | 14 ++++++++++ gcc/testsuite/gfortran.dg/inline_1.f90 | 27 +++++++++++++++++++ gcc/testsuite/gfortran.dg/inline_2.f90 | 14 ++++++++++ 8 files changed, 131 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/gfortran.dg/always_inline_1.f90 create mode 100644 gcc/testsuite/gfortran.dg/always_inline_2.f90 create mode 100644 gcc/testsuite/gfortran.dg/inline_1.f90 create mode 100644 gcc/testsuite/gfortran.dg/inline_2.f90 diff --git a/gcc/fortran/decl.cc b/gcc/fortran/decl.cc index b81d81b2dd1..8b1bb8240f5 100644 --- a/gcc/fortran/decl.cc +++ b/gcc/fortran/decl.cc @@ -12849,6 +12849,8 @@ const ext_attr_t ext_attr_list[] = { { "noinline", EXT_ATTR_NOINLINE, NULL }, { "noreturn", EXT_ATTR_NORETURN, NULL }, { "weak", EXT_ATTR_WEAK, NULL }, + { "inline", EXT_ATTR_INLINE, NULL }, + { "always_inline",EXT_ATTR_ALWAYS_INLINE,NULL }, { NULL, EXT_ATTR_LAST, NULL } }; @@ -12925,6 +12927,27 @@ gfc_match_gcc_attributes (void) sym->attr.ext_attr |= attr.ext_attr; + /* INLINE and ALWAYS_INLINE are incompatible with NOINLINE. In the + middle-end the DECL_UNINLINABLE flag set by NOINLINE always wins, so + the inline request would be silently ignored. Warn and drop it. */ + if (sym->attr.ext_attr & (1 << EXT_ATTR_NOINLINE)) + { + if (sym->attr.ext_attr & (1 << EXT_ATTR_ALWAYS_INLINE)) + { + gfc_warning (0, "Attribute % at %C is " + "incompatible with % for %qs and will " + "be ignored", sym->name); + sym->attr.ext_attr &= ~(1 << EXT_ATTR_ALWAYS_INLINE); + } + if (sym->attr.ext_attr & (1 << EXT_ATTR_INLINE)) + { + gfc_warning (0, "Attribute % at %C is incompatible " + "with % for %qs and will be ignored", + sym->name); + sym->attr.ext_attr &= ~(1 << EXT_ATTR_INLINE); + } + } + if (gfc_match_eos () == MATCH_YES) break; diff --git a/gcc/fortran/gfortran.h b/gcc/fortran/gfortran.h index 8328ff8b34b..d8d8f3faae2 100644 --- a/gcc/fortran/gfortran.h +++ b/gcc/fortran/gfortran.h @@ -877,7 +877,13 @@ enum gfc_omp_at_type OMP_AT_EXECUTION }; -/* Structure and list of supported extension attributes. */ +/* Structure and list of supported extension attributes. + + The bitmask formed from these values (symbol_attribute.ext_attr) is + written to and read from module files, see mio_symbol_attribute. New + attributes must therefore be appended at the end (before EXT_ATTR_LAST) + so that the existing bit positions, and thus module compatibility, are + preserved. */ typedef enum { EXT_ATTR_DLLIMPORT = 0, @@ -890,6 +896,8 @@ typedef enum EXT_ATTR_NOINLINE, EXT_ATTR_NORETURN, EXT_ATTR_WEAK, + EXT_ATTR_INLINE, + EXT_ATTR_ALWAYS_INLINE, 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 12b95f4b19b..c9f45df1882 100644 --- a/gcc/fortran/gfortran.texi +++ b/gcc/fortran/gfortran.texi @@ -3404,6 +3404,14 @@ requires an explicit interface. deprecated procedure, variable or parameter; the warning can be suppressed with @option{-Wno-deprecated-declarations}. @item @code{NOINLINE} -- prevent inlining given function. +@item @code{INLINE} -- hint that the given function should be inlined, while +still respecting the inlining size limits, corresponding to the C @code{inline} +keyword. +@item @code{ALWAYS_INLINE} -- force inlining of a given function, ignoring the +inlining size limits. This is the counterpart of @code{NOINLINE} and +corresponds to the C @code{always_inline} attribute. @code{INLINE} and +@code{ALWAYS_INLINE} are incompatible with @code{NOINLINE}. Specifying both +for the same procedure makes the inline attribute ignored with a warning. @item @code{NORETURN} -- add a hint that a given function cannot return. @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 diff --git a/gcc/fortran/trans-decl.cc b/gcc/fortran/trans-decl.cc index ea12be5dd25..42a5c06d5f0 100644 --- a/gcc/fortran/trans-decl.cc +++ b/gcc/fortran/trans-decl.cc @@ -2673,6 +2673,16 @@ build_function_decl (gfc_symbol * sym, bool global) if (attr.ext_attr & (1 << EXT_ATTR_NOINLINE)) DECL_UNINLINABLE (fndecl) = 1; + /* Mark inline functions. Fortran has no 'inline' keyword, so both INLINE + and ALWAYS_INLINE set DECL_DECLARED_INLINE_P explicitly. ALWAYS_INLINE + additionally disregards the inliner's size limits. Setting only that + would make the middle-end warn that the always-inline function "might + not be inlinable". */ + if (attr.ext_attr & ((1 << EXT_ATTR_INLINE) | (1 << EXT_ATTR_ALWAYS_INLINE))) + DECL_DECLARED_INLINE_P (fndecl) = 1; + if (attr.ext_attr & (1 << EXT_ATTR_ALWAYS_INLINE)) + DECL_DISREGARD_INLINE_LIMITS (fndecl) = 1; + /* Mark noreturn functions. */ if (attr.ext_attr & (1 << EXT_ATTR_NORETURN)) TREE_THIS_VOLATILE (fndecl) = 1; diff --git a/gcc/testsuite/gfortran.dg/always_inline_1.f90 b/gcc/testsuite/gfortran.dg/always_inline_1.f90 new file mode 100644 index 00000000000..fce9ce0781e --- /dev/null +++ b/gcc/testsuite/gfortran.dg/always_inline_1.f90 @@ -0,0 +1,26 @@ +! { dg-do compile } +! { dg-options "-O -fdump-tree-optimized" } +! +! Verify that !GCC$ ATTRIBUTES always_inline forces inlining: the helper +! procedure is inlined into its caller and no standalone call remains. + +subroutine caller(a, n) + implicit none + integer, intent(in) :: n + real, intent(inout) :: a(n) + call helper(a, n) + call helper(a, n) +contains + subroutine helper(x, m) + implicit none + integer, intent(in) :: m + real, intent(inout) :: x(m) +!GCC$ ATTRIBUTES always_inline :: helper + integer :: i + do i = 1, m + x(i) = x(i) + 1.0 + end do + end subroutine helper +end subroutine caller + +! { dg-final { scan-tree-dump-not "helper" "optimized" } } diff --git a/gcc/testsuite/gfortran.dg/always_inline_2.f90 b/gcc/testsuite/gfortran.dg/always_inline_2.f90 new file mode 100644 index 00000000000..2f6040865e6 --- /dev/null +++ b/gcc/testsuite/gfortran.dg/always_inline_2.f90 @@ -0,0 +1,14 @@ +! { dg-do compile } +! +! ALWAYS_INLINE is incompatible with NOINLINE. Specifying both for the same +! procedure must warn and drop ALWAYS_INLINE, whether they appear in one +! directive or in separate directives. + +subroutine foo() +!GCC$ ATTRIBUTES always_inline, noinline :: foo ! { dg-warning "ALWAYS_INLINE. at .1. is incompatible with .NOINLINE." } +end subroutine foo + +subroutine bar() +!GCC$ ATTRIBUTES always_inline :: bar +!GCC$ ATTRIBUTES noinline :: bar ! { dg-warning "ALWAYS_INLINE. at .1. is incompatible with .NOINLINE." } +end subroutine bar diff --git a/gcc/testsuite/gfortran.dg/inline_1.f90 b/gcc/testsuite/gfortran.dg/inline_1.f90 new file mode 100644 index 00000000000..6dc59bf6e2a --- /dev/null +++ b/gcc/testsuite/gfortran.dg/inline_1.f90 @@ -0,0 +1,27 @@ +! { dg-do compile } +! { dg-options "-O2 -fno-inline-small-functions -fno-inline-functions -fno-inline-functions-called-once -fdump-tree-optimized" } +! +! With all automatic inlining disabled the helper procedure would not be +! inlined, but the INLINE attribute marks it as declared-inline, so it is +! inlined anyway and no standalone call remains. + +subroutine caller(a, n) + implicit none + integer, intent(in) :: n + real, intent(inout) :: a(n) + call helper(a, n) + call helper(a, n) +contains + subroutine helper(x, m) + implicit none + integer, intent(in) :: m + real, intent(inout) :: x(m) +!GCC$ ATTRIBUTES inline :: helper + integer :: i + do i = 1, m + x(i) = x(i) + 1.0 + end do + end subroutine helper +end subroutine caller + +! { dg-final { scan-tree-dump-not "helper" "optimized" } } diff --git a/gcc/testsuite/gfortran.dg/inline_2.f90 b/gcc/testsuite/gfortran.dg/inline_2.f90 new file mode 100644 index 00000000000..60da68c947b --- /dev/null +++ b/gcc/testsuite/gfortran.dg/inline_2.f90 @@ -0,0 +1,14 @@ +! { dg-do compile } +! +! INLINE is incompatible with NOINLINE. Specifying both for the same +! procedure must warn and drop INLINE, whether they appear in one directive +! or in separate directives. + +subroutine foo() +!GCC$ ATTRIBUTES inline, noinline :: foo ! { dg-warning "INLINE. at .1. is incompatible with .NOINLINE." } +end subroutine foo + +subroutine bar() +!GCC$ ATTRIBUTES inline :: bar +!GCC$ ATTRIBUTES noinline :: bar ! { dg-warning "INLINE. at .1. is incompatible with .NOINLINE." } +end subroutine bar -- 2.54.0