Add a mem_copy_fixed and mem_set_fixed to mem.h

Probably self-explanatory. I was finding more use cases for the
__builtin_memcpy_inline thing but boy is that ugly.

3 files changed, 25 insertions, 6 deletions

diff --git a/src/mem.h b/src/mem.h
index ae33092..553d390 100644
--- a/src/mem.h
+++ b/src/mem.h
@@ -223,6 +223,28 @@ static forceinline int mem_cmp(const void *restrict x, const void *restrict y,
 #endif
 }
 
+/*
+ * Copies a small fixed-size chunk of memory using some appropriate
+ * compiler-chosen arrangement of move instructions, without calling any
+ * functions. Length must be a compile-time constant.
+ */
+#ifdef __clang__
+#define mem_copy_fixed __builtin_memcpy_inline
+#else
+#define mem_copy_fixed mem_copy // meh
+#endif
+
+/*
+ * Sets a small fixed-size chunk of memory using some appropriate
+ * compiler-chosen arrangement of instructions, without calling any
+ * functions. Length and value must be compile-time constants.
+ */
+#ifdef __clang__
+#define mem_set_fixed __builtin_memcpy_inline
+#else
+#define mem_set_fixed mem_set // meh
+#endif
+
 #endif
 
 // vi: sw=4 ts=4 noet tw=80 cc=80
diff --git a/src/speedrun.c b/src/speedrun.c
index a0849dd..87942e2 100644
--- a/src/speedrun.c
+++ b/src/speedrun.c
@@ -186,8 +186,7 @@ DEF_CCMD_HERE(sst_speedrun_start, "Start recording demos for a speedrun", 0) {
 		else {
 			nameend = pathsz + namelen;
 		}
-		__builtin_memcpy_inline(path + nameend, OS_LIT(".dem"),
-				sizeof(OS_LIT(".dem")));
+		mem_copy_fixed(path + nameend, OS_LIT(".dem"), sizeof(OS_LIT(".dem")));
 		// check for an existing demo file with this name: if we started
 		// recording, then stopped, then started again in quick succession, we
 		// could have one. in this scenario, append a 2-digit counter to the end
diff --git a/src/sst.c b/src/sst.c
index ab78b9c..4cdad5d 100644
--- a/src/sst.c
+++ b/src/sst.c
@@ -197,11 +197,9 @@ c:	mem_copy(r, p + slash + 1, rellen);
 	if_cold (f == -1) { errmsg_errorsys("couldn't open %" fS, path); return; }
 #ifdef _WIN32
 	char buf[19 + PATH_MAX];
-	// XXX: with actual calls to memcpy gone, we need this builtin to produce 4
-	// 4-byte movs from this string; can we expose this in a less hideous way?
-	__builtin_memcpy_inline(buf, "Plugin { file \"", 15);
+	mem_copy_fixed(buf, "Plugin { file \"", 15);
 	for (int i = 0; i < rellen; ++i) buf[i + 15] = relpath[i];
-	__builtin_memcpy_inline(buf + 15 + rellen, "\" }\n", 4);
+	mem_copy_fixed(buf + 15 + rellen, "\" }\n", 4);
 	if_cold (os_write(f, buf, rellen + 19) == -1) { // blegh
 #else
 	struct iovec iov[3] = {