Added @rnd() compile time random function (using the $$rnd() builtin). #2078

lib/std/core/builtin.c3

@@ -30,6 +30,14 @@ typedef EmptySlot = void*;
 macro @is_empty_macro_slot(#arg) @const @builtin => @typeis(#arg, EmptySlot);
 macro @is_valid_macro_slot(#arg) @const @builtin => !@typeis(#arg, EmptySlot);
 
+<*
+ Returns a random value at compile time.
+
+ @ensure return >= 0.0 && return < 1.0
+ @return "A compile time random"
+*>
+macro @rnd() @const @builtin => $$rnd();
+
 /*
  Use `IteratorResult` when reading the end of an iterator, or accessing a result out of bounds.
 */

releasenotes.md

@@ -8,6 +8,7 @@
 - Deprecate uXX and iXX bit suffixes.
 - Add experimental LL / ULL suffixes for int128 and uint128 literals.
 - Allow the right hand side of `|||` and `&&&` be runtime values.
+- Added `@rnd()` compile time random function (using the `$$rnd()` builtin). #2078
 
 ### Fixes
 - Assert triggered when casting from `int[2]` to `uint[2]` #2115

src/compiler/enums.h

@@ -487,6 +487,7 @@ typedef enum
 	BUILTIN_REVERSE,
 	BUILTIN_RETURNADDRESS,
 	BUILTIN_RINT,
+	BUILTIN_RND,
 	BUILTIN_ROUND,
 	BUILTIN_ROUNDEVEN,
 	BUILTIN_SAT_ADD,

src/compiler/llvm_codegen_builtins.c

@@ -1009,6 +1009,7 @@ void llvm_emit_builtin_call(GenContext *c, BEValue *result_value, Expr *expr)
 		case BUILTIN_STR_FIND:
 		case BUILTIN_WIDESTRING_16:
 		case BUILTIN_WIDESTRING_32:
+		case BUILTIN_RND:
 			UNREACHABLE
 		case BUILTIN_NONE:
 			UNREACHABLE

src/compiler/sema_builtins.c

@@ -289,6 +289,20 @@ static bool sema_expr_analyse_syscall(SemaContext *context, Expr *expr)
 	return true;
 }
 
+uint64_t rand_u64()
+{
+	return ((uint64_t)rand() << 48) ^ ((uint64_t)rand() << 32) ^ ((uint64_t)rand() << 16) ^ rand();
+}
+
+bool sema_expr_analyse_rnd(SemaContext *context UNUSED, Expr *expr)
+{
+	uint64_t r = rand_u64();
+	uint64_t mantissa = r >> 11;
+	double val = (double)mantissa / (double)(1ULL << 53); // Not secure random but...
+	expr_rewrite_const_float(expr, type_double, val);
+	return true;
+}
+
 bool sema_expr_analyse_str_hash(SemaContext *context, Expr *expr)
 {
 	Expr *inner = expr->call_expr.arguments[0];
@@ -516,6 +530,8 @@ bool sema_expr_analyse_builtin_call(SemaContext *context, Expr *expr)
 
 	switch (func)
 	{
+		case BUILTIN_RND:
+			return sema_expr_analyse_rnd(context, expr);
 		case BUILTIN_STR_HASH:
 			return sema_expr_analyse_str_hash(context, expr);
 		case BUILTIN_STR_UPPER:
@@ -1124,6 +1140,7 @@ bool sema_expr_analyse_builtin_call(SemaContext *context, Expr *expr)
 		case BUILTIN_TRAP:
 		case BUILTIN_BREAKPOINT:
 		case BUILTIN_UNREACHABLE:
+		case BUILTIN_RND:
 			UNREACHABLE
 	}
 	expr->type = type_add_optional(rtype, optional);
@@ -1147,6 +1164,7 @@ static inline int builtin_expected_args(BuiltinFunction func)
 		case BUILTIN_TRAP:
 		case BUILTIN_BREAKPOINT:
 		case BUILTIN_UNREACHABLE:
+		case BUILTIN_RND:
 			return 0;
 		case BUILTIN_ABS:
 		case BUILTIN_BITREVERSE:

src/compiler/symtab.c

@@ -261,6 +261,7 @@ void symtab_init(uint32_t capacity)
 	builtin_list[BUILTIN_REVERSE] = KW_DEF("reverse");
 	builtin_list[BUILTIN_RETURNADDRESS] = KW_DEF("returnaddress");
 	builtin_list[BUILTIN_RINT] = KW_DEF("rint");
+	builtin_list[BUILTIN_RND] = KW_DEF("rnd");
 	builtin_list[BUILTIN_ROUND] = KW_DEF("round");
 	builtin_list[BUILTIN_ROUNDEVEN] = KW_DEF("roundeven");
 	builtin_list[BUILTIN_SAT_ADD] = KW_DEF("sat_add");

src/main.c

@@ -25,6 +25,7 @@ const char *compiler_exe_name;
 
 int main_real(int argc, const char *argv[])
 {
+	srand((unsigned int)time(NULL));
 	compiler_exe_name = argv[0];
 	bench_begin();