aarch64: Improve vcombine codegen [PR89057]

This patch fixes a codegen regression in the handling of things like:

  __temp.val[0]								     \
    = vcombine_##funcsuffix (__b.val[0],				     \
			     vcreate_##funcsuffix (__AARCH64_UINT64_C (0))); \

in the 64-bit vst[234] functions.  The zero was forced into a
register at expand time, and we relied on combine to fuse the
zero and combine back together into a single combinez pattern.
The problem is that the zero could be hoisted before combine
gets a chance to do its thing.

gcc/
	PR target/89057
	* config/aarch64/aarch64-simd.md (aarch64_combine<mode>): Accept
	aarch64_simd_reg_or_zero for operand 2.  Use the combinez patterns
	to handle zero operands.

gcc/testsuite/
	PR target/89057
	* gcc.target/aarch64/pr89057.c: New test.

(cherry picked from commit b41e6dd50f329b0291457e939d4c0dacd81c82c1)

diff --git a/gcc/config/aarch64/aarch64-simd.md b/gcc/config/aarch64/aarch64-simd.md
index 6d99be39dbcacb0c4dbe5ddce617cb76b734ac93..96dd611196697cdbce3b7c3093b6ce0b73f4e778 100644 (file)
--- a/gcc/config/aarch64/aarch64-simd.md
+++ b/gcc/config/aarch64/aarch64-simd.md
@@ -3332,11 +3332,20 @@
 (define_expand "aarch64_combine<mode>"
   [(match_operand:<VDBL> 0 "register_operand")
    (match_operand:VDC 1 "register_operand")
-   (match_operand:VDC 2 "register_operand")]
+   (match_operand:VDC 2 "aarch64_simd_reg_or_zero")]
   "TARGET_SIMD"
 {
-  aarch64_split_simd_combine (operands[0], operands[1], operands[2]);
-
+  if (operands[2] == CONST0_RTX (<MODE>mode))
+    {
+      if (BYTES_BIG_ENDIAN)
+       emit_insn (gen_aarch64_combinez_be<mode> (operands[0], operands[1],
+                                                 operands[2]));
+      else
+       emit_insn (gen_aarch64_combinez<mode> (operands[0], operands[1],
+                                              operands[2]));
+    }
+  else
+    aarch64_split_simd_combine (operands[0], operands[1], operands[2]);
   DONE;
 }
 )

diff --git a/gcc/testsuite/gcc.target/aarch64/pr89057.c b/gcc/testsuite/gcc.target/aarch64/pr89057.c
new file mode 100644 (file)
index 0000000..1e20024
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/pr89057.c
@@ -0,0 +1,16 @@
+/* { dg-options "-O3" } */
+
+#include <arm_neon.h>
+
+void
+f (int32_t *dst, int32_t *src, int n)
+{
+  for (int i = 0; i < n; ++i)
+    {
+      int32x2x3_t a = vld3_s32 (src + i * 6);
+      int32x2x3_t b = { a.val[2], a.val[1], a.val[0] };
+      vst3_s32 (dst + i * 6, b);
+    }
+}
+
+/* { dg-final { scan-assembler-not {\tins\t} } } */