- Raw vaargs with optional return not lowered correctly #2819

releasenotes.md

@@ -122,6 +122,7 @@
 - Slice overrun detected late hit codegen assert #2822
 - Compile time dereference of a constant slice was too generous #2821
 - Constant deref of subscript had inserted checks #2818
+- Raw vaargs with optional return not lowered correctly #2819
 
 ### Stdlib changes
 - Add `ThreadPool` join function to wait for all threads to finish in the pool without destroying the threads.

src/compiler/llvm_codegen_expr.c

@@ -5817,7 +5817,7 @@ INLINE void llvm_emit_call_invocation(GenContext *c, BEValue *result_value,
 			for (unsigned i = 0; i < vararg_count; i++)
 			{
 				ABIArgInfo *info = abi_varargs[index];
-				BEValue value_copy = values[i + param_count];
+				BEValue value_copy = values[i + param_count - start];
 				llvm_emit_parameter(c, arg_values, &arg_count, info, &value_copy);
 				index++;
 			}
@@ -5828,7 +5828,7 @@ INLINE void llvm_emit_call_invocation(GenContext *c, BEValue *result_value,
 			for (unsigned i = 0; i < vararg_count; i++)
 			{
 				REMINDER("Varargs should be expanded correctly");
-				arg_values[arg_count++] = llvm_load_value_store(c, &values[i + param_count]);
+				arg_values[arg_count++] = llvm_load_value_store(c, &values[i + param_count - start]);
 			}
 		}
 	}

test/test_suite/abi/raw_vaarg_with_optional_return.c3t

@@ -0,0 +1,24 @@
+// #target: linux-aarch64
+module test;
+extern fn float? printf(char*,...);
+fn int main()
+{
+	float a = 12.3;
+	(void)printf("", a);
+	return 0;
+}
+
+/* #expect: test.ll
+
+declare i64 @printf(ptr, ptr, ...) #0
+
+define i32 @main() #0 {
+entry:
+  %a = alloca float, align 4
+  %retparam = alloca float, align 4
+  store float 0x40289999A0000000, ptr %a, align 4
+  %0 = load float, ptr %a, align 4
+  %fpfpext = fpext float %0 to double
+  %1 = call i64 (ptr, ptr, ...) @printf(ptr %retparam, ptr @.str, double %fpfpext)
+  ret i32 0
+}