From 472b7ef7e6db4bdd4717ff5b44b63e233853bb06 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Sat, 16 Jun 2018 19:14:14 -0400
Subject: [PATCH] disable byval

---
 src/codegen.cpp              | 21 ---------------------
 test/behavior.zig            |  1 +
 test/cases/byval_arg_var.zig | 27 +++++++++++++++++++++++++++
 3 files changed, 28 insertions(+), 21 deletions(-)
 create mode 100644 test/cases/byval_arg_var.zig

diff --git a/src/codegen.cpp b/src/codegen.cpp
index fedfcfa744..425cdac024 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -326,13 +326,6 @@ static void addLLVMArgAttr(LLVMValueRef arg_val, unsigned param_index, const cha
     return addLLVMAttr(arg_val, param_index + 1, attr_name);
 }
 
-static void addLLVMCallsiteAttr(LLVMValueRef call_instr, unsigned param_index, const char *attr_name) {
-    unsigned kind_id = LLVMGetEnumAttributeKindForName(attr_name, strlen(attr_name));
-    assert(kind_id != 0);
-    LLVMAttributeRef llvm_attr = LLVMCreateEnumAttribute(LLVMGetGlobalContext(), kind_id, 0);
-    LLVMAddCallSiteAttribute(call_instr, param_index + 1, llvm_attr);
-}
-
 static bool is_symbol_available(CodeGen *g, Buf *name) {
     return g->exported_symbol_names.maybe_get(name) == nullptr && g->external_prototypes.maybe_get(name) == nullptr;
 }
@@ -581,11 +574,6 @@ static LLVMValueRef fn_llvm_value(CodeGen *g, FnTableEntry *fn_table_entry) {
         if (param_type->id == TypeTableEntryIdPointer) {
             addLLVMArgAttr(fn_table_entry->llvm_value, (unsigned)gen_index, "nonnull");
         }
-        // Note: byval is disabled on windows due to an LLVM bug:
-        // https://github.com/ziglang/zig/issues/536
-        if (is_byval && g->zig_target.os != OsWindows) {
-            addLLVMArgAttr(fn_table_entry->llvm_value, (unsigned)gen_index, "byval");
-        }
     }
 
     uint32_t err_ret_trace_arg_index = get_err_ret_trace_arg_index(g, fn_table_entry);
@@ -3114,15 +3102,6 @@ static LLVMValueRef ir_render_call(CodeGen *g, IrExecutable *executable, IrInstr
     }
 
 
-    for (size_t param_i = 0; param_i < fn_type_id->param_count; param_i += 1) {
-        FnGenParamInfo *gen_info = &fn_type->data.fn.gen_param_info[param_i];
-        // Note: byval is disabled on windows due to an LLVM bug:
-        // https://github.com/ziglang/zig/issues/536
-        if (gen_info->is_byval && g->zig_target.os != OsWindows) {
-            addLLVMCallsiteAttr(result, (unsigned)gen_info->gen_index, "byval");
-        }
-    }
-
     if (instruction->is_async) {
         LLVMValueRef payload_ptr = LLVMBuildStructGEP(g->builder, instruction->tmp_ptr, err_union_payload_index, "");
         LLVMBuildStore(g->builder, result, payload_ptr);
diff --git a/test/behavior.zig b/test/behavior.zig
index eb8b643bb7..096c07b2e0 100644
--- a/test/behavior.zig
+++ b/test/behavior.zig
@@ -13,6 +13,7 @@ comptime {
     _ = @import("cases/bugs/656.zig");
     _ = @import("cases/bugs/828.zig");
     _ = @import("cases/bugs/920.zig");
+    _ = @import("cases/byval_arg_var.zig");
     _ = @import("cases/cast.zig");
     _ = @import("cases/const_slice_child.zig");
     _ = @import("cases/coroutines.zig");
diff --git a/test/cases/byval_arg_var.zig b/test/cases/byval_arg_var.zig
new file mode 100644
index 0000000000..826b9cc9e5
--- /dev/null
+++ b/test/cases/byval_arg_var.zig
@@ -0,0 +1,27 @@
+const std = @import("std");
+
+var result: []const u8 = "wrong";
+
+test "aoeu" {
+    start();
+    blowUpStack(10);
+
+    std.debug.assert(std.mem.eql(u8, result, "string literal"));
+}
+
+fn start() void {
+    foo("string literal");
+}
+
+fn foo(x: var) void {
+    bar(x);
+}
+
+fn bar(x: var) void {
+    result = x;
+}
+
+fn blowUpStack(x: u32) void {
+    if (x == 0) return;
+    blowUpStack(x - 1);
+}