[PATCH] build: Implement --with-multilib-list for avr target

[Matt Jacobson via Gcc-patches]

The AVR target builds a lot of multilib variants of target libraries by default,
and I found myself wanting to use the --with-multilib-list argument to limit
what I was building, to shorten build times.  This patch implements that option
for the AVR target.

Tested by configuring and building an AVR compiler and target libs on macOS.

I don't have commit access, so if this patch is suitable, I'd need someone else
to commit it for me.  Thanks.

gcc/ChangeLog:

2020-06-07  Matt Jacobson  <mhjacob...@me.com>

        * config.gcc: For the AVR target, populate TM_MULTILIB_CONFIG.
        * config/avr/genmultilib.awk: Add ability to filter generated multilib
        list.
        * config/avr/t-avr: Pass TM_MULTILIB_CONFIG to genmultilib.awk.
        * configure.ac: Update help string for --with-multilib-list.
        * configure: Regenerate.


diff --git a/gcc/config.gcc b/gcc/config.gcc
index 6a349965c..fd83996a4 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -4201,6 +4201,13 @@ case "${target}" in
                fi
                ;;
 
+       avr-*-*)
+               # Handle --with-multilib-list.
+               if test "x${with_multilib_list}" != xdefault; then
+                       TM_MULTILIB_CONFIG="${with_multilib_list}"
+               fi
+       ;;
+
     csky-*-*)
        supported_defaults="cpu endian float"
        ;;
diff --git a/gcc/config/avr/genmultilib.awk b/gcc/config/avr/genmultilib.awk
index 2d07c0e53..ad8814602 100644
--- a/gcc/config/avr/genmultilib.awk
+++ b/gcc/config/avr/genmultilib.awk
@@ -67,6 +67,16 @@ BEGIN {
 
     dir_long_double = "long-double"   (96 - with_long_double)
     opt_long_double = "mlong-double=" (96 - with_long_double)
+
+    if (with_multilib_list != "")
+    {
+       split(with_multilib_list, multilib_list, ",")
+
+       for (i in multilib_list)
+       {
+           multilibs[multilib_list[i]] = 1
+       }
+    }
 }
 
 ##################################################################
@@ -137,6 +147,9 @@ BEGIN {
        if (core == "avr1")
            next
 
+       if (with_multilib_list != "" && !(core in multilibs))
+           next
+
        option[core] = "mmcu=" core
 
        m_options  = m_options m_sep option[core]
@@ -150,6 +163,9 @@ BEGIN {
     if (core == "avr1")
        next
 
+    if (with_multilib_list != "" && !(core in multilibs))
+       next
+
     opts = option[core]
 
     # split device specific feature list
diff --git a/gcc/config/avr/t-avr b/gcc/config/avr/t-avr
index 3e1a1ba68..7d20c6107 100644
--- a/gcc/config/avr/t-avr
+++ b/gcc/config/avr/t-avr
@@ -127,6 +127,7 @@ t-multilib-avr: $(srcdir)/config/avr/genmultilib.awk \
                -v HAVE_LONG_DOUBLE64=$(HAVE_LONG_DOUBLE64)             \
                -v with_double=$(WITH_DOUBLE)                           \
                -v with_long_double=$(WITH_LONG_DOUBLE)                 \
+               -v with_multilib_list=$(TM_MULTILIB_CONFIG)             \
                -f $< $< $(AVR_MCUS) > $@
 
 include t-multilib-avr
diff --git a/gcc/configure.ac b/gcc/configure.ac
index 715fcba04..c3ed65df7 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -1106,7 +1106,7 @@ if test x"$enable_hsa" = x1 ; then
 fi
 
 AC_ARG_WITH(multilib-list,
-[AS_HELP_STRING([--with-multilib-list], [select multilibs (AArch64, SH and 
x86-64 only)])],
+[AS_HELP_STRING([--with-multilib-list], [select multilibs (AArch64, AVR, i386, 
or1k, RISC-V, SH, and x86-64 only)])],
 :,
 with_multilib_list=default)