From ccf0ab0ef6da95eae71c0dbc2c0ded0d5d674a40 Mon Sep 17 00:00:00 2001
From: kcbanner <kcbanner@gmail.com>
Date: Thu, 29 Dec 2022 16:41:48 -0500
Subject: cbe: use callconv(.C) for zig.g stub functions, use zig.h function
 for windows teb instead of syscall

---
 lib/std/os/windows.zig     | 18 +++---------------
 lib/std/zig/system/x86.zig |  4 ++--
 lib/zig.h                  | 14 ++++++++++++++
 3 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/lib/std/os/windows.zig b/lib/std/os/windows.zig
index efd7c805cf..268e13a379 100644
--- a/lib/std/os/windows.zig
+++ b/lib/std/os/windows.zig
@@ -1776,6 +1776,8 @@ pub fn UnlockFile(
     }
 }
 
+extern fn zig_x86_64_windows_teb() callconv(.C) *anyopaque;
+
 pub fn teb() *TEB {
     return switch (native_arch) {
         .x86 => asm volatile (
@@ -1784,21 +1786,7 @@ pub fn teb() *TEB {
         ),
         .x86_64 => blk: {
             if (builtin.zig_backend == .stage2_c) {
-                // TODO: __asm is not available on x64 MSVC. This is a workaround
-                // until an intrinsic to read the gs register is available
-                var thread_information: THREAD_BASIC_INFORMATION = undefined;
-                const result = ntdll.NtQueryInformationThread(
-                    kernel32.GetCurrentThread(),
-                    .ThreadBasicInformation,
-                    &thread_information,
-                    @sizeOf(THREAD_BASIC_INFORMATION),
-                    null);
-
-                if (result == .SUCCESS) {
-                    break :blk @ptrCast(*TEB, @alignCast(@alignOf(TEB), thread_information.TebBaseAddress));
-                } else {
-                    unexpectedStatus(result) catch unreachable;
-                }
+                break :blk @ptrCast(*TEB, @alignCast(@alignOf(TEB), zig_x86_64_windows_teb()));
             } else {
                 break :blk asm volatile (
                     \\ movq %%gs:0x30, %[ptr]
diff --git a/lib/std/zig/system/x86.zig b/lib/std/zig/system/x86.zig
index 9a9aa54975..634a04fb43 100644
--- a/lib/std/zig/system/x86.zig
+++ b/lib/std/zig/system/x86.zig
@@ -528,7 +528,7 @@ const CpuidLeaf = packed struct {
     edx: u32,
 };
 
-extern fn zig_x86_cpuid(leaf_id: u32, subid: u32, eax: *u32, ebx: *u32, ecx: *u32, edx: *u32) void;
+extern fn zig_x86_cpuid(leaf_id: u32, subid: u32, eax: *u32, ebx: *u32, ecx: *u32, edx: *u32) callconv(.C) void;
 
 fn cpuid(leaf_id: u32, subid: u32) CpuidLeaf {
     // valid for both x86 and x86_64
@@ -553,7 +553,7 @@ fn cpuid(leaf_id: u32, subid: u32) CpuidLeaf {
     return .{ .eax = eax, .ebx = ebx, .ecx = ecx, .edx = edx };
 }
 
-extern fn zig_x86_get_xcr0() u32;
+extern fn zig_x86_get_xcr0() callconv(.C) u32;
 
 // Read control register 0 (XCR0). Used to detect features such as AVX.
 fn getXCR0() u32 {
diff --git a/lib/zig.h b/lib/zig.h
index 645850aa0e..d54ad285d6 100644
--- a/lib/zig.h
+++ b/lib/zig.h
@@ -2349,6 +2349,20 @@ zig_msvc_atomics_128op(u128, max)
 
 /* ========================= Special Case Intrinsics ========================= */
 
+#if (_MSC_VER && _M_X64) || defined(__x86_64__)
+
+static inline void* zig_x86_64_windows_teb() {
+#if _MSC_VER
+    return __readgsqword(0x30);
+#else
+    void* teb;
+    __asm volatile(" movq %%gs:0x30, %[ptr]": [ptr]"=r"(teb)::);
+    return teb;
+#endif
+}
+
+#endif
+
 #if (_MSC_VER && (_M_IX86 || _M_X64)) || defined(__i386__) || defined(__x86_64__)
 
 static inline void zig_x86_cpuid(zig_u32 leaf_id, zig_u32 subid, zig_u32* eax, zig_u32* ebx, zig_u32* ecx, zig_u32* edx) {
-- 
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