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* [PATCH] arm: Add missing early clobber to MVE vrev64q_m patterns
@ 2022-10-03 10:43 Christophe Lyon
  2022-10-03 12:50 ` Richard Earnshaw
  0 siblings, 1 reply; 2+ messages in thread
From: Christophe Lyon @ 2022-10-03 10:43 UTC (permalink / raw)
  To: gcc-patches; +Cc: Kyrylo.Tkachov, Christophe Lyon

Like the non-predicated vrev64q patterns, mve_vrev64q_m_<supf><mode>
and mve_vrev64q_m_f<mode> need an early clobber constraint, otherwise
we can generate an unpredictable instruction:

Warning: 64-bit element size and same destination and source operands makes instruction UNPREDICTABLE
when calling vrevq64_m* with the same first and second arguments.

Regression-tested on arm-none-eabi, bootstap in progress on
armv8l-unknown-linux-gnueabihf.

OK for trunk?

Thanks,

Christophe

gcc/ChangeLog:

	* config/arm/mve.md: (mve_vrev64q_m_<supf><mode>): Add early
          clobber.
	  (mve_vrev64q_m_f<mode>): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.target/arm/mve/intrinsics/vrev64q_m_s16-clobber.c: New test.
---
 gcc/config/arm/mve.md                           |  4 ++--
 .../arm/mve/intrinsics/vrev64q_m_s16-clobber.c  | 17 +++++++++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/arm/mve/intrinsics/vrev64q_m_s16-clobber.c

diff --git a/gcc/config/arm/mve.md b/gcc/config/arm/mve.md
index 714178609f7..62186f124da 100644
--- a/gcc/config/arm/mve.md
+++ b/gcc/config/arm/mve.md
@@ -3503,7 +3503,7 @@ (define_insn "mve_vqshlq_m_r_<supf><mode>"
 ;;
 (define_insn "mve_vrev64q_m_<supf><mode>"
   [
-   (set (match_operand:MVE_2 0 "s_register_operand" "=w")
+   (set (match_operand:MVE_2 0 "s_register_operand" "=&w")
 	(unspec:MVE_2 [(match_operand:MVE_2 1 "s_register_operand" "0")
 		       (match_operand:MVE_2 2 "s_register_operand" "w")
 		       (match_operand:<MVE_VPRED> 3 "vpr_register_operand" "Up")]
@@ -4598,7 +4598,7 @@ (define_insn "mve_vrev32q_m_<supf><mode>"
 ;;
 (define_insn "mve_vrev64q_m_f<mode>"
   [
-   (set (match_operand:MVE_0 0 "s_register_operand" "=w")
+   (set (match_operand:MVE_0 0 "s_register_operand" "=&w")
 	(unspec:MVE_0 [(match_operand:MVE_0 1 "s_register_operand" "0")
 		       (match_operand:MVE_0 2 "s_register_operand" "w")
 		       (match_operand:<MVE_VPRED> 3 "vpr_register_operand" "Up")]
diff --git a/gcc/testsuite/gcc.target/arm/mve/intrinsics/vrev64q_m_s16-clobber.c b/gcc/testsuite/gcc.target/arm/mve/intrinsics/vrev64q_m_s16-clobber.c
new file mode 100644
index 00000000000..6464c96181d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/mve/intrinsics/vrev64q_m_s16-clobber.c
@@ -0,0 +1,17 @@
+/* { dg-require-effective-target arm_v8_1m_mve_fp_ok } */
+/* { dg-add-options arm_v8_1m_mve_fp } */
+/* { dg-additional-options "-O2" } */
+
+#include "arm_mve.h"
+
+int16x8_t
+foo (int16x8_t a, mve_pred16_t p)
+{
+  return vrev64q_m_s16 (a, a, p);
+}
+
+float16x8_t
+foo2 (float16x8_t a, mve_pred16_t p)
+{
+  return vrev64q_m_f16 (a, a, p);
+}
-- 
2.34.1


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