From f950d763a160d7ee333dde75ff61c9ac6597c803 Mon Sep 17 00:00:00 2001
From: Jacob G-W <jacoblevgw@gmail.com>
Date: Fri, 12 Nov 2021 18:10:13 -0500
Subject: [PATCH] stage2 x86_64 codegen: don't count return registers as
 callee-preserved

---
 src/arch/x86_64/CodeGen.zig |  4 ++--
 src/arch/x86_64/bits.zig    | 19 +++++++++----------
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/src/arch/x86_64/CodeGen.zig b/src/arch/x86_64/CodeGen.zig
index fac9a53a14..2de2796983 100644
--- a/src/arch/x86_64/CodeGen.zig
+++ b/src/arch/x86_64/CodeGen.zig
@@ -1902,10 +1902,10 @@ fn airCall(self: *Self, inst: Air.Inst.Index) !void {
                     try self.register_manager.getReg(reg, null);
                     try self.genSetReg(arg_ty, reg, arg_mcv);
                 },
-                .stack_offset => {
+                .stack_offset => |off| {
                     // Here we need to emit instructions like this:
                     // mov     qword ptr [rsp + stack_offset], x
-                    return self.fail("TODO implement calling with parameters in memory", .{});
+                    try self.genSetStack(arg_ty, off, arg_mcv);
                 },
                 .ptr_stack_offset => {
                     return self.fail("TODO implement calling with MCValue.ptr_stack_offset arg", .{});
diff --git a/src/arch/x86_64/bits.zig b/src/arch/x86_64/bits.zig
index df221595f3..7b09dc59e7 100644
--- a/src/arch/x86_64/bits.zig
+++ b/src/arch/x86_64/bits.zig
@@ -84,15 +84,13 @@ pub const Register = enum(u7) {
     /// Returns the index into `callee_preserved_regs`.
     pub fn allocIndex(self: Register) ?u4 {
         return switch (self) {
-            .rax, .eax, .ax, .al => 0,
-            .rcx, .ecx, .cx, .cl => 1,
-            .rdx, .edx, .dx, .dl => 2,
-            .rsi, .esi, .si  => 3,
-            .rdi, .edi, .di => 4,
-            .r8, .r8d, .r8w, .r8b => 5,
-            .r9, .r9d, .r9w, .r9b => 6,
-            .r10, .r10d, .r10w, .r10b => 7,
-            .r11, .r11d, .r11w, .r11b => 8,
+            .rcx, .ecx, .cx, .cl => 0,
+            .rsi, .esi, .si  => 1,
+            .rdi, .edi, .di => 2,
+            .r8, .r8d, .r8w, .r8b => 3,
+            .r9, .r9d, .r9w, .r9b => 4,
+            .r10, .r10d, .r10w, .r10b => 5,
+            .r11, .r11d, .r11w, .r11b => 6,
             else => null,
         };
     }
@@ -145,7 +143,8 @@ pub const Register = enum(u7) {
 // zig fmt: on
 
 /// These registers belong to the called function.
-pub const callee_preserved_regs = [_]Register{ .rax, .rcx, .rdx, .rsi, .rdi, .r8, .r9, .r10, .r11 };
+/// TODO should the return_regs be in this array?
+pub const callee_preserved_regs = [_]Register{ .rcx, .rsi, .rdi, .r8, .r9, .r10, .r11 };
 pub const c_abi_int_param_regs = [_]Register{ .rdi, .rsi, .rdx, .rcx, .r8, .r9 };
 pub const c_abi_int_return_regs = [_]Register{ .rax, .rdx };