This patch adds -mprune-vectab as a new target option.
It acts as a front end for the linker's --prune-vectab option
that has been added as https://sourceware.org/PR34679.
The compiler option has only an effect when the linker
actually supports --prune-vectab, which is tested for in
configure.ac.
Ok for trunk?
FYI, the respective Binutils patch is
https://sourceware.org/pipermail/binutils/2026-September/151688.html
which also needs approval.
Johann
--
gcc/
* configure.ac [target=avr-*.*]: Test linker for --prune-vectab,
and AC_DEFINE HAVE_LD_AVR_PRUNE_VECTAB if supported.
* config.in: Rebuild.
* configure: Rebuild.
* config/avr/avr.opt (-mprune-vectab): New target option.
* config/avr/specs.h (LINK_SPEC): Add %(link_prune_vectab).
* config/avr/gen-avr-mmcu-specs.cc (link_prune_vectab)
[HAVE_LD_AVR_PRUNE_VECTAB]: Emit new spec definition.
* config/avr/avr.opt.urls: Rebuild.
* doc/invoke.texi (AVR Options): Document -mprune-vectab.diff --git a/gcc/config.in b/gcc/config.in
index b90caa0dd57..d4d864e858f 100644
--- a/gcc/config.in
+++ b/gcc/config.in
@@ -1726,6 +1726,12 @@
#endif
+/* Define if your linker supports --prune-vectab. */
+#ifndef USED_FOR_TARGET
+#undef HAVE_LD_AVR_PRUNE_VECTAB
+#endif
+
+
/* Define if your linker supports -z bndplt */
#ifndef USED_FOR_TARGET
#undef HAVE_LD_BNDPLT_SUPPORT
diff --git a/gcc/config/avr/avr.opt b/gcc/config/avr/avr.opt
index c94385f5370..4c81aa8df2c 100644
--- a/gcc/config/avr/avr.opt
+++ b/gcc/config/avr/avr.opt
@@ -99,6 +99,10 @@ mrelax
Target Optimization
Optimization. Relax branches.
+mprune-vectab
+Target Optimization
+Optimization. Prune AVR-LibC vector table provided relaxation is on.
+
mpmem-wrap-around
Target
Make the linker relaxation machine assume that a program counter wrap-around occurs.
diff --git a/gcc/config/avr/avr.opt.urls b/gcc/config/avr/avr.opt.urls
index e0c725e8d1a..97cbc1bc923 100644
--- a/gcc/config/avr/avr.opt.urls
+++ b/gcc/config/avr/avr.opt.urls
@@ -48,6 +48,9 @@ UrlSuffix(gcc/AVR-Options.html#index-mtiny-stack)
mrelax
UrlSuffix(gcc/AVR-Options.html#index-mrelax)
+mprune-vectab
+UrlSuffix(gcc/AVR-Options.html#index-mprune-vectab)
+
mpmem-wrap-around
UrlSuffix(gcc/AVR-Options.html#index-mpmem-wrap-around)
diff --git a/gcc/config/avr/gen-avr-mmcu-specs.cc b/gcc/config/avr/gen-avr-mmcu-specs.cc
index 470d40538e5..a6ea5632aad 100644
--- a/gcc/config/avr/gen-avr-mmcu-specs.cc
+++ b/gcc/config/avr/gen-avr-mmcu-specs.cc
@@ -376,6 +376,12 @@ print_mcu (const avr_mcu_t *mcu, const McuInfo &mi)
if (mcu->text_section_start != 0x0)
fprintf (f, "\t%%{!Ttext:-Ttext 0x%lX}", 0UL + mcu->text_section_start);
fprintf (f, "\n\n");
+
+#if defined (WITH_AVRLIBC) && defined(HAVE_LD_AVR_PRUNE_VECTAB)
+ fprintf (f, "*link_prune_vectab:\n");
+ fprintf (f, "\t%%{!r:%%{mprune-vectab:--prune-vectab}}");
+ fprintf (f, "\n\n");
+#endif // Have --prune-vectab
}
// -m[no-]rodata-in-ram affects linking. Sanity check its usage.
diff --git a/gcc/config/avr/specs.h b/gcc/config/avr/specs.h
index b50f7040941..dfa212c072a 100644
--- a/gcc/config/avr/specs.h
+++ b/gcc/config/avr/specs.h
@@ -65,6 +65,7 @@ along with GCC; see the file COPYING3. If not see
"%(link_data_start) " \
"%(link_text_start) " \
"%(link_relax) " \
+ "%(link_prune_vectab) " \
"%(link_pmem_wrap) " \
"%(link_rodata_in_ram) " \
"%(link_no_call_main) " \
diff --git a/gcc/configure b/gcc/configure
index 2d211a0beae..b1dd8fa48ad 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -29375,6 +29375,19 @@ $as_echo "$as_me: WARNING: support for avrxmega4_flmap requires Binutils 2.42 or
$as_echo "$as_me: WARNING: see \`config.log' for details" >&2;}
fi
rm -f conftest.s conftest.o conftest.elf
+
+ # Check for linker --prune-vectab.
+ gcc_cv_ld_avr_prune_vectab=no
+ { $as_echo "$as_me:${as_lineno-$LINENO}: checking linker for --prune-vectab support" >&5
+$as_echo_n "checking linker for --prune-vectab support... " >&6; }
+ if $gcc_cv_ld --help 2>&1 | grep -- '--prune-vectab' > /dev/null; then
+ gcc_cv_ld_avr_prune_vectab=yes
+
+$as_echo "#define HAVE_LD_AVR_PRUNE_VECTAB 1" >>confdefs.h
+
+ fi
+ { $as_echo "$as_me:${as_lineno-$LINENO}: result: $gcc_cv_ld_avr_prune_vectab" >&5
+$as_echo "$gcc_cv_ld_avr_prune_vectab" >&6; }
;;
cris-*-*)
diff --git a/gcc/configure.ac b/gcc/configure.ac
index a4878c4a9f9..d6f07f4ddb8 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -4880,6 +4880,16 @@ EOF
AC_MSG_WARN([[see `config.log' for details]])
fi
rm -f conftest.s conftest.o conftest.elf
+
+ # Check for linker --prune-vectab.
+ gcc_cv_ld_avr_prune_vectab=no
+ AC_MSG_CHECKING(linker for --prune-vectab support)
+ if $gcc_cv_ld --help 2>&1 | grep -- '--prune-vectab' > /dev/null; then
+ gcc_cv_ld_avr_prune_vectab=yes
+ AC_DEFINE(HAVE_LD_AVR_PRUNE_VECTAB, 1,
+ [Define if your linker supports --prune-vectab.])
+ fi
+ AC_MSG_RESULT($gcc_cv_ld_avr_prune_vectab)
;;
cris-*-*)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index feec1561850..1f5f7fb1ffc 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -990,7 +990,7 @@ Objective-C and Objective-C++ Dialects}.
-mcall-prologues -mgas-isr-prologues -mint8 -mflmap
-mdouble=@var{bits} -mlong-double=@var{bits} -mno-call-main
-mn_flash=@var{size} -mfract-convert-truncate -mno-interrupts
--mmain-is-OS_task -moptimize -mrelax -mpmem-wrap-around
+-mmain-is-OS_task -moptimize -mrelax -mpmem-wrap-around -mprune-vectab
-mrmw -mstrict-addr-space-subsets -mstrict-X -mtiny-stack
-mrodata-in-ram -msplit-bit-shift -msplit-ldst -mshort-calls
-mskip-bug -muse-nonzero-bits -nodevicelib -nodevicespecs
@@ -24510,6 +24510,24 @@ differ from instructions in the assembly code.
Relaxing must be turned on if linker stubs are needed, see the
section on @code{EIND} and linker stubs below.
+@opindex mprune-vectab
+@item -mprune-vectab
+Remove unused entries in the AVR-LibC interrupt vector table during relaxing.
+Setting @option{-mprune-vectab} just adds the @option{--prune-vectab} option
+to the linker's command line, provided the required GNU Binutils
+support (@w{@uref{https://sourceware.org/PR34679,,PR34679}}) is available.
+Otherwise, or when relaxing is not enabled, the option has no effect.
+
+What is not supported are jumps like
+@example
+ JMP 0x18
+@end example
+that target a vector table entry. Use code like
+@example
+ JMP __vectors + 0x18
+@end example
+instead.
+
@opindex mstrict-addr-space-subsets
@item -mstrict-addr-space-subsets
Impose strict named address space subset relations. Without this option,
