[RS6000] Fix ICE caused by rs6000_savres_strategy thinko

[Alan Modra]

rev 235672 (git cffc0b35) changed the condition for SAVE_MULTIPLE/
STORE_MULTIPLE, wrongly allowing a single reg.  Bootstrapped and
regression tested powerpc64-linux.  OK to apply?

Incidentally, the added testcase function shows a regression in -m32
-Os code quality that I'll fix sometime soon.

gcc/
        * config/rs6000/rs6000.c (rs6000_savres_strategy): Correct condition
        for SAVE_MULTIPLE/STORE_MULTIPLE.
gcc/testsuite/
        * gcc.target/powerpc/savres.c: Add func using a single gpr.

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index e94aa66..6fa8a0c 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -23438,7 +23438,7 @@ rs6000_savres_strategy (rs6000_stack_t *info,
   if (TARGET_MULTIPLE
       && !TARGET_POWERPC64
       && !(TARGET_SPE_ABI && info->spe_64bit_regs_used)
-      && info->first_gp_reg_save != 32)
+      && info->first_gp_reg_save < 31)
     {
       /* Prefer store multiple for saves over out-of-line routines,
         since the store-multiple instruction will always be smaller.  */
diff --git a/gcc/testsuite/gcc.target/powerpc/savres.c 
b/gcc/testsuite/gcc.target/powerpc/savres.c
index 5ebadf6..9432ed7 100644
--- a/gcc/testsuite/gcc.target/powerpc/savres.c
+++ b/gcc/testsuite/gcc.target/powerpc/savres.c
@@ -447,6 +447,16 @@ void s_r (void)
   __asm __volatile ("#%0" : "=m" (a) : : "r30", "r31");
 }
 
+void s_r31 (void)
+{
+  char a[33];
+#ifndef NO_BODY
+  TRASH_GPR (r31);
+  __asm__ __volatile__ ("#%0" : : "r" (r31));
+#endif
+  __asm __volatile ("#%0" : "=m" (a) : : "r31");
+}
+
 void s_c (void)
 {
   char a[33];
@@ -1154,6 +1164,8 @@ main (void)
   VERIFY_REGS;
   s_r ();
   VERIFY_REGS;
+  s_r31 ();
+  VERIFY_REGS;
   s_c ();
   VERIFY_REGS;
   s_0 ();

-- 
Alan Modra
Australia Development Lab, IBM