[gcc/devel/gccgo] [AArch64] Reject invalid subregs involving partial SVE modes

[gcc/devel/gccgo] [AArch64] Reject invalid subregs involving partial SVE modes

[Ian Lance Taylor]

https://gcc.gnu.org/g:76607e7e5f5ef67e4a469fdf2a320118ff2fa25a

commit 76607e7e5f5ef67e4a469fdf2a320118ff2fa25a
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Thu Dec 19 13:36:16 2019 +0000

    [AArch64] Reject invalid subregs involving partial SVE modes
    
    When adding partial SVE modes, I'd remembered to handle reloads
    in a similar way to full big-endian SVE vectors, but forgot the
    just-as-important mode-change rules.
    
    2019-12-19  Richard Sandiford  <richard.sandiford@arm.com>
    
    gcc/
    	* config/aarch64/aarch64.c (aarch64_can_change_mode_class):
    	Don't allow changes between partial SVE modes and other kinds
    	of mode.  Don't allow changes between two partial SVE modes
    	if they have different container or element sizes.
    
    gcc/testsuite/
    	* gcc.target/aarch64/sve/mixed_size_8.c: New test.
    
    From-SVN: r279572

Diff:
---
 gcc/ChangeLog                                      |  7 +++++
 gcc/config/aarch64/aarch64.c                       | 25 ++++++++++++++--
 gcc/testsuite/ChangeLog                            |  4 +++
 .../gcc.target/aarch64/sve/mixed_size_8.c          | 34 ++++++++++++++++++++++
 4 files changed, 67 insertions(+), 3 deletions(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 63a5ee4..542bdf6 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,12 @@
 2019-12-19  Richard Sandiford  <richard.sandiford@arm.com>
 
+	* config/aarch64/aarch64.c (aarch64_can_change_mode_class):
+	Don't allow changes between partial SVE modes and other kinds
+	of mode.  Don't allow changes between two partial SVE modes
+	if they have different container or element sizes.
+
+2019-12-19  Richard Sandiford  <richard.sandiford@arm.com>
+
 	* config/aarch64/aarch64.c (aarch64_function_value_1): New function,
 	split out from...
 	(aarch64_function_value): ...here.  Handle partial SVE modes by
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index cf6aa7e..88baf96 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -21457,11 +21457,30 @@ static bool
 aarch64_can_change_mode_class (machine_mode from,
 			       machine_mode to, reg_class_t)
 {
+  unsigned int from_flags = aarch64_classify_vector_mode (from);
+  unsigned int to_flags = aarch64_classify_vector_mode (to);
+
+  bool from_sve_p = (from_flags & VEC_ANY_SVE);
+  bool to_sve_p = (to_flags & VEC_ANY_SVE);
+
+  bool from_partial_sve_p = from_sve_p && (from_flags & VEC_PARTIAL);
+  bool to_partial_sve_p = to_sve_p && (to_flags & VEC_PARTIAL);
+
+  /* Don't allow changes between partial SVE modes and other modes.
+     The contents of partial SVE modes are distributed evenly across
+     the register, whereas GCC expects them to be clustered together.  */
+  if (from_partial_sve_p != to_partial_sve_p)
+    return false;
+
+  /* Similarly reject changes between partial SVE modes that have
+     different patterns of significant and insignificant bits.  */
+  if (from_partial_sve_p
+      && (aarch64_sve_container_bits (from) != aarch64_sve_container_bits (to)
+	  || GET_MODE_UNIT_SIZE (from) != GET_MODE_UNIT_SIZE (to)))
+    return false;
+
   if (BYTES_BIG_ENDIAN)
     {
-      bool from_sve_p = aarch64_sve_data_mode_p (from);
-      bool to_sve_p = aarch64_sve_data_mode_p (to);
-
       /* Don't allow changes between SVE data modes and non-SVE modes.
 	 See the comment at the head of aarch64-sve.md for details.  */
       if (from_sve_p != to_sve_p)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3385971..7d47488 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,9 @@
 2019-12-19  Richard Sandiford  <richard.sandiford@arm.com>
 
+	* gcc.target/aarch64/sve/mixed_size_8.c: New test.
+
+2019-12-19  Richard Sandiford  <richard.sandiford@arm.com>
+
 	* gcc.target/aarch64/sve/pcs/gnu_vectors_3.c: New test.
 
 2019-12-19  Feng Xue  <fxue@os.amperecomputing.com>
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/mixed_size_8.c b/gcc/testsuite/gcc.target/aarch64/sve/mixed_size_8.c
new file mode 100644
index 0000000..f9e95d3
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sve/mixed_size_8.c
@@ -0,0 +1,34 @@
+/* { dg-options "-O2 -msve-vector-bits=512" } */
+
+typedef int int32x16_t __attribute__((vector_size(64)));
+typedef int int32x8_t __attribute__((vector_size(32)));
+
+int32x8_t
+f1 (int32x16_t x)
+{
+  union u { int32x16_t full; int32x8_t pair[2]; } u;
+  u.full = x | 2;
+  return u.pair[0] + (int32x8_t) { 1, 2, 3, 4, 5, 6, 7, 8 };
+}
+
+int32x8_t
+f2 (int32x16_t x)
+{
+  union u { int32x16_t full; int32x8_t pair[2]; } u;
+  u.full = x | 2;
+  return u.pair[1] + (int32x8_t) { 1, 2, 3, 4, 5, 6, 7, 8 };
+}
+
+/* We could do something more efficient than spill the int32x16_t and
+   reload the int32x8_t.  The important thing is that we don't do
+   something like:
+
+	orr	z0.s, z0.s, #2
+	index	z1.d, #1, #1
+	add	z0.s, z0.s, z1.s
+	st1w	z0.d, p0, [x8]
+
+   We're supposed to add z1 to one half of the ORR result instead.  */
+/* { dg-final { scan-assembler-times {\tld1w\tz[0-9]+\.d} 2 } } */
+/* { dg-final { scan-assembler-times {\tindex\tz[0-9]+\.d} 2 } } */
+/* { dg-final { scan-assembler-times {\tst1w\tz[0-9]+\.d} 2 } } */