aarch64: Specify that FEAT_MOPS sequences clobber CC

According to the architecture pseudocode the FEAT_MOPS sequences overwrite the NZCV flags
as par of their operation, so GCC needs to model that in the relevant RTL patterns.
For the testcase:
void g();
void foo (int a, size_t N, char *__restrict__ in,
         char *__restrict__ out)
{
  if (a != 3)
    __builtin_memcpy (out, in, N);
  if (a > 3)
    g ();
}

we will currently generate:
foo:
        cmp     w0, 3
        bne     .L6
.L1:
        ret
.L6:
        cpyfp   [x3]!, [x2]!, x1!
        cpyfm   [x3]!, [x2]!, x1!
        cpyfe   [x3]!, [x2]!, x1!
        ble     .L1 // Flags reused after CPYF* sequence
        b       g

This is wrong as the result of cmp needs to be recalculated after the MOPS sequence.
With this patch we'll insert a "cmp w0, 3" before the ble, similar to what clang does.

Bootstrapped and tested on aarch64-none-linux-gnu.
Pushing to trunk and to the GCC 12 branch after some baking time.

gcc/ChangeLog:

	* config/aarch64/aarch64.md (aarch64_cpymemdi): Specify clobber of CC reg.
	(*aarch64_cpymemdi): Likewise.
	(aarch64_movmemdi): Likewise.
	(aarch64_setmemdi): Likewise.
	(*aarch64_setmemdi): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/mops_5.c: New test.
	* gcc.target/aarch64/mops_6.c: Likewise.
	* gcc.target/aarch64/mops_7.c: Likewise.

diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index 76b6898..8a18405 100644 (file)
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -1592,6 +1592,7 @@
      [(set (match_operand 2) (const_int 0))
       (clobber (match_dup 3))
       (clobber (match_dup 4))
+      (clobber (reg:CC CC_REGNUM))
       (set (match_operand 0)
           (unspec:BLK [(match_operand 1) (match_dup 2)] UNSPEC_CPYMEM))])]
   "TARGET_MOPS"
@@ -1605,6 +1606,7 @@
   [(set (match_operand:DI 2 "register_operand" "+&r") (const_int 0))
    (clobber (match_operand:DI 0 "register_operand" "+&r"))
    (clobber (match_operand:DI 1 "register_operand" "+&r"))
+   (clobber (reg:CC CC_REGNUM))
    (set (mem:BLK (match_dup 0))
         (unspec:BLK [(mem:BLK (match_dup 1)) (match_dup 2)] UNSPEC_CPYMEM))]
   "TARGET_MOPS"
@@ -1635,6 +1637,7 @@
    (set (match_operand:DI 2 "register_operand" "+&r") (const_int 0))
    (clobber (match_operand:DI 0 "register_operand" "+&r"))
    (clobber (match_operand:DI 1 "register_operand" "+&r"))
+   (clobber (reg:CC CC_REGNUM))
    (set (mem:BLK (match_dup 0))
         (unspec:BLK [(mem:BLK (match_dup 1)) (match_dup 2)] UNSPEC_MOVMEM))])]
  "TARGET_MOPS"
@@ -1680,6 +1683,7 @@
   [(parallel
      [(set (match_operand 2) (const_int 0))
       (clobber (match_dup 3))
+      (clobber (reg:CC CC_REGNUM))
       (set (match_operand 0)
           (unspec:BLK [(match_operand 1)
                        (match_dup 2)] UNSPEC_SETMEM))])]
@@ -1692,6 +1696,7 @@
 (define_insn "*aarch64_setmemdi"
   [(set (match_operand:DI 2 "register_operand" "+&r") (const_int 0))
    (clobber (match_operand:DI 0 "register_operand" "+&r"))
+   (clobber (reg:CC CC_REGNUM))
    (set (mem:BLK (match_dup 0))
         (unspec:BLK [(match_operand:QI 1 "aarch64_reg_or_zero" "rZ")
                     (match_dup 2)] UNSPEC_SETMEM))]

diff --git a/gcc/testsuite/gcc.target/aarch64/mops_5.c b/gcc/testsuite/gcc.target/aarch64/mops_5.c
new file mode 100644 (file)
index 0000000..8a26267
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/mops_5.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=armv8.6-a+mops" } */
+
+#include <stddef.h>
+
+void g();
+void foo (int a, size_t N, char *__restrict__ in,
+         char *__restrict__ out)
+{
+  if (a != 3)
+    __builtin_memcpy (out, in, N);
+  if (a > 3)
+    g ();
+}
+
+/* { dg-final { scan-assembler-times {cmp\tw0, *} 2 } } */
+

diff --git a/gcc/testsuite/gcc.target/aarch64/mops_6.c b/gcc/testsuite/gcc.target/aarch64/mops_6.c
new file mode 100644 (file)
index 0000000..c6c9a54
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/mops_6.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=armv8.6-a+mops" } */
+
+#include <stddef.h>
+
+void g();
+void foo (int a, size_t N, char *__restrict__ in,
+         char *__restrict__ out)
+{
+  if (a != 3)
+    __builtin_memmove (out, in, N);
+  if (a > 3)
+    g ();
+}
+
+/* { dg-final { scan-assembler-times {cmp\tw0, *} 2 } } */
+

diff --git a/gcc/testsuite/gcc.target/aarch64/mops_7.c b/gcc/testsuite/gcc.target/aarch64/mops_7.c
new file mode 100644 (file)
index 0000000..79720ca
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/mops_7.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=armv8.6-a+mops" } */
+
+#include <stddef.h>
+
+void g();
+void foo (int a, size_t N, char *__restrict__ out)
+{
+  if (a != 3)
+    __builtin_memset (out, 0, N);
+  if (a > 3)
+    g ();
+}
+
+/* { dg-final { scan-assembler-times {cmp\tw0, *} 2 } } */
+