https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90329
--- Comment #35 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
One more thing, if I add to start of the DTRTRI function
INTERFACE
SUBROUTINE DTRTI2( UPLO, DIAG, N, A, LDA, INFO )
CHARACTER DIAG, UPLO
INTEGER INFO, LDA, N
DOUBLE PRECISION A( LDA, * )
END SUBROUTINE
END INTERFACE
INTERFACE
SUBROUTINE XERBLA( FOO, BAR )
CHARACTER FOO
INTEGER BAR
END SUBROUTINE
END INTERFACE
INTERFACE
SUBROUTINE DTRMM ( S1, S2, S3, S4, I1, I2, D1, A, I3, D2, I4 )
CHARACTER S1, S2, S3, S4
INTEGER I1, I2, I3, I4
DOUBLE PRECISION D1, D2
DOUBLE PRECISION A( I3, * )
END SUBROUTINE
END INTERFACE
INTERFACE
SUBROUTINE DTRSM ( S1, S2, S3, S4, I1, I2, D1, D2, I3, D3, I4 )
CHARACTER S1, S2, S3, S4
INTEGER I1, I2, I3, I4
DOUBLE PRECISION D1, D2, D3
END SUBROUTINE
END INTERFACE
INTERFACE
FUNCTION LSAME ( S1, S2 )
CHARACTER S1, S2
LOGICAL LSAME
END FUNCTION
END INTERFACE
INTERFACE
FUNCTION ILAENV ( I1, S1, S2, I2, I3, I4, I5 )
INTEGER I1, I2, I3, I4, I5, ILAENV
CHARACTER S1, S2
END FUNCTION
END INTERFACE
and remove
LOGICAL LSAME
INTEGER ILAENV
EXTERNAL LSAME, ILAENV
EXTERNAL DTRMM, DTRSM, DTRTI2, XERBLA
then it is tail call optimized back to somewhere in between r164328 (still
doesn't tail call it) and r164450 (already tail calls it). What matters is not
whether the exact function/subroutine we are calling in the tail call position
has interface or not, tail call optimization doesn't care about that, but the
presence or absence of TYPE_ARG_TYPES on the function types that are called
matters for the alias analysis (r268991 vs. r268992):
-ESCAPED = uplo
-ESCAPED = &STRING
+callarg(30) = uplo
+callarg(30) = callarg(30) + UNKNOWN
+callarg(30) = *callarg(30) + UNKNOWN
+CALLUSED(28) = callarg(30)
+CALLCLOBBERED(29) = callarg(30)
+*callarg(30) = NONLOCAL
+callarg(31) = &STRING
+callarg(31) = callarg(31) + UNKNOWN
+callarg(31) = *callarg(31) + UNKNOWN
+CALLUSED(28) = callarg(31)
+CALLCLOBBERED(29) = callarg(31)
+*callarg(31) = NONLOCAL
and similarly for many other arguments. So, if we wanted to narrow the
workaround more, we could do the DECL_HIDDEN_STRING_LENGTH setting conditional
on whether the function has any calls to Fortran implicitly prototyped
function.
Or if we add a command line switch, have different modes, one which would
assume sane callers, another one that would do it only for functions that call
implicitly prototyped functions and another that would do it always like the
committed workaround does.
On the other side, those unprototyped calls could come from inlined calls too,
though as a heuristics it could work, usually the codebase either is modern
fortran, or is not, and given that the workaround is for undefined behavior, we
are always free to do anything we want.
