[gcc r10-9452] aarch64: Fix status return logic in RNG intrinsics

[Kyrylo Tkachov]

https://gcc.gnu.org/g:2f87268c34ff3150908a4b3319ba068b83af2f24

commit r10-9452-g2f87268c34ff3150908a4b3319ba068b83af2f24
Author: Kyrylo Tkachov <kyrylo.tkachov@arm.com>
Date:   Wed Mar 17 18:21:05 2021 +0000

    aarch64: Fix status return logic in RNG intrinsics
    
    There is a bug with the RNG intrinsics in their return code. The definition says:
    
    "Stores a 64-bit random number into the object pointed to by the argument and returns zero.
    If the implementation could not generate a random number within a reasonable period of time
    the object pointed to by the input is set to zero and a non-zero value is returned."
    
    This means we should be testing whether to return non-zero with:
    CSET W0, EQ
    rather than NE.
    
    This patch fixes that.
    
    gcc/ChangeLog:
    
            * config/aarch64/aarch64-builtins.c (aarch64_expand_rng_builtin): Use EQ
            to compare against CC_REG rather than NE.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/aarch64/acle/rng_2.c: New test.
    
    (cherry picked from commit f7581eb38eeaa8af64f3cdfe2faf764f5883f16f)

Diff:
---
 gcc/config/aarch64/aarch64-builtins.c         |  2 +-
 gcc/testsuite/gcc.target/aarch64/acle/rng_2.c | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/gcc/config/aarch64/aarch64-builtins.c b/gcc/config/aarch64/aarch64-builtins.c
index b0d36f9934d..d92157dff02 100644
--- a/gcc/config/aarch64/aarch64-builtins.c
+++ b/gcc/config/aarch64/aarch64-builtins.c
@@ -1805,7 +1805,7 @@ aarch64_expand_rng_builtin (tree exp, rtx target, int fcode, int ignore)
     return target;
 
   rtx cc_reg = gen_rtx_REG (CC_Zmode, CC_REGNUM);
-  rtx cmp_rtx = gen_rtx_fmt_ee (NE, SImode, cc_reg, const0_rtx);
+  rtx cmp_rtx = gen_rtx_fmt_ee (EQ, SImode, cc_reg, const0_rtx);
   emit_insn (gen_aarch64_cstoresi (target, cmp_rtx, cc_reg));
   return target;
 }
diff --git a/gcc/testsuite/gcc.target/aarch64/acle/rng_2.c b/gcc/testsuite/gcc.target/aarch64/acle/rng_2.c
new file mode 100644
index 00000000000..206136cfc1f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/acle/rng_2.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=armv8.5-a+rng" } */
+
+#include <arm_acle.h>
+
+int test_rndr (uint64_t *addr)
+{
+  return  __rndr (addr);
+}
+
+/* { dg-final { scan-assembler-times {cset\t...?, eq} 1 } } */
+