[AArch64] Prefer FPRs over GPRs for CLASTB

This patch makes the SVE CLASTB GPR alternative more expensive than the
FPR alternative in order to avoid unnecessary cross-file moves.  It also
fixes the prefix used to print the FPR; <vw> only handles 32-bit and
64-bit elements.

2019-08-07  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/aarch64-sve.md (fold_extract_last_<mode>):
	Disparage the GPR alternative relative to the FPR one.
	Fix handling of 8-bit and 16-bit FPR values.

gcc/testsuite/
	* gcc.target/aarch64/sve/clastb_8.c: New test.

From-SVN: r274191

gcc/ChangeLog

 2019-08-07  Richard Sandiford  <richard.sandiford@arm.com>
 
+	* config/aarch64/aarch64-sve.md (fold_extract_last_<mode>):
+	Disparage the GPR alternative relative to the FPR one.
+	Fix handling of 8-bit and 16-bit FPR values.
+
+2019-08-07  Richard Sandiford  <richard.sandiford@arm.com>
+
 	* config/aarch64/iterators.md (BITWISEV): Delete.
 	(SVE_INT_REDUCTION, SVE_FP_REDUCTION): New int iterators.
 	(optab): Handle UNSPEC_UMAXV, UNSPEC_UMINV, UNSPEC_SMAXV,

gcc/config/aarch64/aarch64-sve.md

@@ -3104,7 +3104,7 @@
 ;; Set operand 0 to the last active element in operand 3, or to tied
 ;; operand 1 if no elements are active.
 (define_insn "fold_extract_last_<mode>"
-  [(set (match_operand:<VEL> 0 "register_operand" "=r, w")
+  [(set (match_operand:<VEL> 0 "register_operand" "=?r, w")
 	(unspec:<VEL>
 	  [(match_operand:<VEL> 1 "register_operand" "0, 0")
 	   (match_operand:<VPRED> 2 "register_operand" "Upl, Upl")
@@ -3113,7 +3113,7 @@
   "TARGET_SVE"
   "@
    clastb\t%<vwcore>0, %2, %<vwcore>0, %3.<Vetype>
-   clastb\t%<vw>0, %2, %<vw>0, %3.<Vetype>"
+   clastb\t%<Vetype>0, %2, %<Vetype>0, %3.<Vetype>"
 )
 
 ;; -------------------------------------------------------------------------

gcc/testsuite/ChangeLog

+2019-08-07  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* gcc.target/aarch64/sve/clastb_8.c: New test.
+
 2019-08-07  Uroš Bizjak  <ubizjak@gmail.com>
 
 	PR target/91385

gcc/testsuite/gcc.target/aarch64/sve/clastb_8.c

+/* { dg-do assemble { target aarch64_asm_sve_ok } } */
+/* { dg-options "-O2 -ftree-vectorize -msve-vector-bits=256 --save-temps" } */
+
+#include <stdint.h>
+
+#define TEST_TYPE(TYPE) \
+  void \
+  test_##TYPE (TYPE *ptr, TYPE *a, TYPE *b, TYPE min_v) \
+  { \
+    TYPE last = *ptr; \
+    for (int i = 0; i < 1024; i++) \
+      if (a[i] < min_v) \
+	last = b[i]; \
+    *ptr = last; \
+  }
+
+TEST_TYPE (uint8_t);
+TEST_TYPE (uint16_t);
+TEST_TYPE (uint32_t);
+TEST_TYPE (uint64_t);
+
+/* { dg-final { scan-assembler {\tclastb\t(b[0-9]+), p[0-7], \1, z[0-9]+\.b\n} } } */
+/* { dg-final { scan-assembler {\tclastb\t(h[0-9]+), p[0-7], \1, z[0-9]+\.h\n} } } */
+/* { dg-final { scan-assembler {\tclastb\t(s[0-9]+), p[0-7], \1, z[0-9]+\.s\n} } } */
+/* { dg-final { scan-assembler {\tclastb\t(d[0-9]+), p[0-7], \1, z[0-9]+\.d\n} } } */