While working on another MSR-related patch, I noticed that
aarch64_write_sysregdi's constraints allowed zero, but its
predicate didn't. This could in principle lead to an ICE
during or after RA, since "Z" allows the RA to rematerialise
a known zero directly into the instruction.
The usual techniques for exposing a bug like that didn't work in this
case, since the optimisers seem to make no attempt to remove redundant
zero moves (at least not for these unspec_volatiles). But the problem
still seems worth fixing pre-emptively.
Tested on aarch64-linux-gnu & pushed.
Richard
gcc/
* config/aarch64/aarch64.md (aarch64_read_sysregti): Change
the source predicate to aarch64_reg_or_zero.
gcc/testsuite/
* gcc.target/aarch64/acle/rwsr-4.c: New test.
* gcc.target/aarch64/acle/rwsr-armv8p9.c: Avoid read of uninitialized
variable.
---
gcc/config/aarch64/aarch64.md | 2 +-
gcc/testsuite/gcc.target/aarch64/acle/rwsr-4.c | 15 +++++++++++++++
.../gcc.target/aarch64/acle/rwsr-armv8p9.c | 4 +---
3 files changed, 17 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/aarch64/acle/rwsr-4.c
diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index f8d82cee903..39655ea5e39 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -659,7 +659,7 @@ (define_insn "aarch64_read_sysregti"
(define_insn "aarch64_write_sysregdi"
[(unspec_volatile:DI [(match_operand 0 "aarch64_sysreg_string" "")
- (match_operand:DI 1 "register_operand" "rZ")]
+ (match_operand:DI 1 "aarch64_reg_or_zero" "rZ")]
UNSPEC_SYSREG_WDI)]
""
"msr\t%0, %x1"
diff --git a/gcc/testsuite/gcc.target/aarch64/acle/rwsr-4.c
b/gcc/testsuite/gcc.target/aarch64/acle/rwsr-4.c
new file mode 100644
index 00000000000..52fb603f3cf
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/acle/rwsr-4.c
@@ -0,0 +1,15 @@
+/* { dg-options "-O" } */
+
+#include <stdint.h>
+#include <arm_acle.h>
+
+void f();
+void g()
+{
+ int64_t x = 0;
+ __arm_wsr64("tpidr_el0", x);
+ f();
+ __arm_wsr64("tpidr_el0", x);
+}
+
+/* { dg-final { scan-assembler-times {\tmsr\t[^,]+, xzr\n} 2 } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/acle/rwsr-armv8p9.c
b/gcc/testsuite/gcc.target/aarch64/acle/rwsr-armv8p9.c
index e2f297bbeeb..c49fbb5368e 100644
--- a/gcc/testsuite/gcc.target/aarch64/acle/rwsr-armv8p9.c
+++ b/gcc/testsuite/gcc.target/aarch64/acle/rwsr-armv8p9.c
@@ -3,10 +3,8 @@
/* { dg-options "-O2 -march=armv8.9-a" } */
#include <arm_acle.h>
void
-readwrite_armv8p9a_sysregs ()
+readwrite_armv8p9a_sysregs (long long int a)
{
- long long int a;
-
/* Write-only system registers. */
__arm_wsr64 ("pmzr_el0", a); /* { dg-final { scan-assembler
"msr\ts3_3_c9_c13_4, x0" } } */
--
2.25.1
