rs6000: Unaligned stfiwx on older CPUs (PR89746)

The "classic" PowerPCs (6xx/7xx) are not STRICT_ALIGNMENT, but their
floating point units are.  This is not normally a problem, the ABIs
make everything FP aligned.  The RTL patterns converting FP to integer
however get a potentially unaligned destination, and we do not want to
do an stfiwx on that on such older CPUs.

This fixes it.  It does not change anything for TARGET_MFCRF targets
(POWER4 and later).  It also won't change anything for strict-alignment
targets, or CPUs without hardware FP of course, or CPUs that do not
implement stfiwx (older 4xx/5xx/8xx).

It does not change the corresponding fixuns* pattern, because that can
not be enabled on any CPU that cannot handle unaligned FP well.


	PR target/89746
	* config/rs6000/rs6000.md (fix_trunc<mode>si2_stfiwx): If we have a
	non-TARGET_MFCRF target, and the dest is memory but not 32-bit aligned,
	go via a stack temporary.

From-SVN: r269802

gcc/ChangeLog

+2018-03-19  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR target/89746
+	* config/rs6000/rs6000.md (fix_trunc<mode>si2_stfiwx): If we have a
+	non-TARGET_MFCRF target, and the dest is memory but not 32-bit aligned,
+	go via a stack temporary.
+
 2019-03-19  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/89378

gcc/config/rs6000/rs6000.md

@@ -5639,13 +5639,13 @@
     tmp = gen_reg_rtx (DImode);
 
   emit_insn (gen_fctiwz_<mode> (tmp, src));
-  if (MEM_P (dest))
+  if (MEM_P (dest) && (TARGET_MFCRF || MEM_ALIGN (dest) >= 32))
     {
       dest = rs6000_force_indexed_or_indirect_mem (dest);
       emit_insn (gen_stfiwx (dest, tmp));
       DONE;
     }
-  else if (TARGET_POWERPC64 && (TARGET_MFPGPR || TARGET_DIRECT_MOVE))
+  else if (TARGET_POWERPC64 && (TARGET_MFPGPR || TARGET_DIRECT_MOVE) && !MEM_P (dest))
     {
       dest = gen_lowpart (DImode, dest);
       emit_move_insn (dest, tmp);