[committed] aarch64: Fix mismatched SVE predicate modes [PR94606]

[Richard Sandiford]

For this testcase we ended up generating the invalid rtl:

(insn 10 9 11 2 (set (reg:VNx16BI 105)
        (and:VNx16BI (xor:VNx16BI (reg:VNx8BI 103)
                (reg:VNx16BI 104))
            (reg:VNx16BI 104))) "/tmp/bar.c":9:12 -1
     (nil))

Fixed by taking the VNx16BI lowpart.  It's safe to do that here because
the gp (r104) masks out the extra odd-indexed bits.

Tested on aarch64-linux-gnu and aarch64_be-elf, pushed.

Richard


2020-04-16  Richard Sandiford  <richard.sandif...@arm.com>

gcc/
        PR target/94606
        * config/aarch64/aarch64.c (aarch64_expand_sve_const_pred_eor): Take
        the VNx16BI lowpart of the recursively-generated constant.

gcc/testsuite/
        PR target/94606
        * gcc.dg/vect/pr94606.c: New test.
---
 gcc/config/aarch64/aarch64.c        |  1 +
 gcc/testsuite/gcc.dg/vect/pr94606.c | 13 +++++++++++++
 2 files changed, 14 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/vect/pr94606.c

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 4af562a81ea..d0a41c286cd 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -4742,6 +4742,7 @@ aarch64_expand_sve_const_pred_eor (rtx target, 
rtx_vector_builder &builder,
   /* EOR the result with an ELT_SIZE PTRUE.  */
   rtx mask = aarch64_ptrue_all (elt_size);
   mask = force_reg (VNx16BImode, mask);
+  inv = gen_lowpart (VNx16BImode, inv);
   target = aarch64_target_reg (target, VNx16BImode);
   emit_insn (gen_aarch64_pred_z (XOR, VNx16BImode, target, mask, inv, mask));
   return target;
diff --git a/gcc/testsuite/gcc.dg/vect/pr94606.c 
b/gcc/testsuite/gcc.dg/vect/pr94606.c
new file mode 100644
index 00000000000..f0e7c4cd0e8
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr94606.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-march=armv8.2-a+sve -msve-vector-bits=256" { 
target aarch64*-*-* } } */
+
+const short mask[] = { 0, 0, 0, 0, 0, 0, 0, 0,
+                      0, 0, 0, 1, 1, 1, 1, 1 };
+
+int
+foo (short *restrict x, short *restrict y)
+{
+  for (int i = 0; i < 16; ++i)
+    if (mask[i])
+      x[i] += y[i];
+}