[gcc r13-7985] LoongArch: Define macro CLEAR_INSN_CACHE.

[gcc r13-7985] LoongArch: Define macro CLEAR_INSN_CACHE.

[LuluCheng]

https://gcc.gnu.org/g:319e887bdddfb8b9244f9310a54c1f08b7e8f0e8

commit r13-7985-g319e887bdddfb8b9244f9310a54c1f08b7e8f0e8
Author: Lulu Cheng <chenglulu@loongson.cn>
Date:   Mon Oct 23 09:07:32 2023 +0800

    LoongArch: Define macro CLEAR_INSN_CACHE.
    
    LoongArch's microstructure ensures cache consistency by hardware.
    Due to out-of-order execution, "ibar" is required to ensure the visibility of the
    store (invalidated icache) executed by this CPU before "ibar" (to the instance).
    "ibar" will not invalidate the icache, so the start and end parameters are not Affect
    "ibar" performance.
    
    gcc/ChangeLog:
    
            * config/loongarch/loongarch.h (CLEAR_INSN_CACHE): New definition.
    
    (cherry picked from commit 5697ed0327f23d2e2ec4f7beec3b3d02f463173c)

Diff:
---
 gcc/config/loongarch/loongarch.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gcc/config/loongarch/loongarch.h b/gcc/config/loongarch/loongarch.h
index f81678756465..f0db67f8c7b8 100644
--- a/gcc/config/loongarch/loongarch.h
+++ b/gcc/config/loongarch/loongarch.h
@@ -1157,3 +1157,8 @@ struct GTY (()) machine_function
   (TARGET_HARD_FLOAT_ABI ? (TARGET_DOUBLE_FLOAT_ABI ? 8 : 4) : 0)
 
 #define FUNCTION_VALUE_REGNO_P(N) ((N) == GP_RETURN || (N) == FP_RETURN)
+
+/* LoongArch maintains ICache/DCache coherency by hardware,
+   we just need "ibar" to avoid instruction hazard here.  */
+#undef  CLEAR_INSN_CACHE
+#define CLEAR_INSN_CACHE(beg, end) __builtin_loongarch_ibar (0)