[compiler-rt] [compiler-rt] Inline __NR_riscv_flush_icache instead of including linux/unistd.h (PR #193645)

[Mark Zhuang via llvm-commits]

https://github.com/zqb-all created https://github.com/llvm/llvm-project/pull/193645

Avoid the dependency on kernel headers to get __NR_riscv_flush_icache, mirroring the existing approach used for __ARM_NR_cacheflush.

Assisted-by: Claude Sonnet 4.6

>From be1e4481dce51a4bc68d7b3e32830e2a4d553d69 Mon Sep 17 00:00:00 2001
From: Mark Zhuang <mark.zhuang at spacemit.com>
Date: Thu, 23 Apr 2026 00:00:46 +0800
Subject: [PATCH] [compiler-rt] Inline __NR_riscv_flush_icache instead of
 including <linux/unistd.h>

Avoid the dependency on kernel headers to get __NR_riscv_flush_icache,
mirroring the existing approach used for __ARM_NR_cacheflush.

Assisted-by: Claude Sonnet 4.6
---
 compiler-rt/lib/builtins/clear_cache.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/compiler-rt/lib/builtins/clear_cache.c b/compiler-rt/lib/builtins/clear_cache.c
index 1d673ede279e4..c21b73405d1a0 100644
--- a/compiler-rt/lib/builtins/clear_cache.c
+++ b/compiler-rt/lib/builtins/clear_cache.c
@@ -48,11 +48,6 @@ uintptr_t GetCurrentProcess(void);
 #include <unistd.h>
 #endif
 
-#if defined(__linux__) && defined(__riscv)
-// to get platform-specific syscall definitions
-#include <linux/unistd.h>
-#endif
-
 // The compiler generates calls to __clear_cache() when creating
 // trampoline functions on the stack for use with nested functions.
 // It is expected to invalidate the instruction cache for the
@@ -185,6 +180,10 @@ void __clear_cache(void *start, void *end) {
   for (uintptr_t dword = start_dword; dword < end_dword; dword += dword_size)
     __asm__ volatile("flush %0" : : "r"(dword));
 #elif defined(__riscv) && defined(__linux__)
+  // Inlined for the same reason as __ARM_NR_cacheflush above.
+#ifndef __NR_riscv_flush_icache
+#define __NR_riscv_flush_icache 259
+#endif
   // See: arch/riscv/include/asm/cacheflush.h, arch/riscv/kernel/sys_riscv.c
   register void *start_reg __asm("a0") = start;
   const register void *end_reg __asm("a1") = end;