[PATCH] alpha: enable gnu-indirect-function support for alpha-linux

Add alpha*-* to the list of targets that default to
--enable-gnu-indirect-function on glibc-based Linux systems.  This
sets HAVE_GNU_INDIRECT_FUNCTION=1, making targetm.has_ifunc_p() return
true and enabling __attribute__((ifunc)) support.

No Alpha backend changes are needed — the generic ifunc machinery in
varasm.cc handles emission, and alpha/elf.h already provides the
required ASM_OUTPUT_TYPE_DIRECTIVE and ASM_OUTPUT_DEF macros.

Requires binutils support for R_ALPHA_IRELATIVE and glibc dynamic
linker support for the new relocation.

The binutils patch series adding STT_GNU_IFUNC and R_ALPHA_IRELATIVE
support has been sent to the binutils list:

  https://sourceware.org/pipermail/binutils/2026-August/150713.html

glibc dynamic linker support for R_ALPHA_IRELATIVE will follow.

Tested by cross-compiling gcc.dg/attr-ifunc-{1..5}.c and
g++.dg/ext/attr-ifunc-{1..5}.C targeting alpha-linux-gnu.  GCC
correctly emits .type foo, @gnu_indirect_function and the resulting
binaries contain STT_GNU_IFUNC symbols.  Runtime tests require the
pending glibc dynamic linker patch.
---
 gcc/config.gcc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git ./gcc/config.gcc ./gcc/config.gcc
index 6968d666b89..aade3c6b152 100644
--- ./gcc/config.gcc
+++ ./gcc/config.gcc
@@ -3685,7 +3685,7 @@ case ${target} in
         ;;
 *-*-linux* | *-*-gnu*)
 	case ${target} in
-	aarch64*-* | arm*-* | i[34567]86-* | powerpc*-* | s390*-* | sparc*-* | x86_64-* | loongarch*-*)
+	aarch64*-* | alpha*-* | arm*-* | i[34567]86-* | powerpc*-* | s390*-* | sparc*-* | x86_64-* | loongarch*-*)
 		default_gnu_indirect_function=yes
 		;;
 	esac
-- 
2.54.0