RISC-V: Re-enable -msave-restore for shared libraries.

This re-enables -msave-restore for shared libraries, and uses the
t-slibgcc-libgcc file to get the save-restore routines included directly
in shared libraries so that we don't need to indirect through the PLT
to reach them, which doesn't work.

	gcc/
	* config/riscv/riscv.c (riscv_option_override): Revert 2019-08-30
	change.

	libgcc/
	* config.host (riscv*-*-linux*): Add t-slibgcc-libgcc to tmake_file.
	(riscv*-*-freebsd*): Likewise.

From-SVN: r275478

gcc/ChangeLog

+2019-09-06  Jim Wilson  <jimw@sifive.com>
+
+	* config/riscv/riscv.c (riscv_option_override): Revert 2019-08-30
+	change.
+
 2019-09-06  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* config/rs6000/rs6000.md (unspec): Delete UNSPEC_MV_CR_OV.

gcc/config/riscv/riscv.c

@@ -4636,16 +4636,6 @@ riscv_option_override (void)
     error ("%<-mriscv-attribute%> RISC-V ELF attribute requires GNU as 2.32"
 	   " [%<-mriscv-attribute%>]");
 #endif
-
-  /* The save-restore routines use t0 which is clobbered by the plt header,
-     so we can't use them when building shared libraries.  */
-  if (TARGET_SAVE_RESTORE && flag_pic && TARGET_PLT)
-    {
-      target_flags &= ~MASK_SAVE_RESTORE;
-      if (target_flags_explicit & MASK_SAVE_RESTORE)
-	warning (0, "%<-msave-restore%> disabled; not supported with PLT "
-		 "based shared libraries");
-    }
 }
 
 /* Implement TARGET_CONDITIONAL_REGISTER_USAGE.  */

libgcc/ChangeLog

+2019-09-06  Jim Wilson  <jimw@sifive.com>
+
+	* config.host (riscv*-*-linux*): Add t-slibgcc-libgcc to tmake_file.
+	(riscv*-*-freebsd*): Likewise.
+
 2019-09-03  Ulrich Weigand  <uweigand@de.ibm.com>
 
 	* config.host: Remove references to spu.

libgcc/config.host

@@ -1201,12 +1201,12 @@ pru-*-*)
 	tm_file="$tm_file pru/pru-abi.h"
 	;;
 riscv*-*-linux*)
-	tmake_file="${tmake_file} riscv/t-softfp${host_address} t-softfp riscv/t-elf riscv/t-elf${host_address}"
+	tmake_file="${tmake_file} riscv/t-softfp${host_address} t-softfp riscv/t-elf riscv/t-elf${host_address} t-slibgcc-libgcc"
 	extra_parts="$extra_parts crtbegin.o crtend.o crti.o crtn.o crtendS.o crtbeginT.o"
 	md_unwind_header=riscv/linux-unwind.h
 	;;
 riscv*-*-freebsd*)
-	tmake_file="${tmake_file} riscv/t-softfp${host_address} t-softfp riscv/t-elf riscv/t-elf${host_address}"
+	tmake_file="${tmake_file} riscv/t-softfp${host_address} t-softfp riscv/t-elf riscv/t-elf${host_address} t-slibgcc-libgcc"
 	extra_parts="$extra_parts crtbegin.o crtend.o crti.o crtn.o crtendS.o crtbeginT.o"
 	;;
 riscv*-*-*)