1 files changed, 85 insertions, 0 deletions
diff --git a/vendor/compiler_builtins/src/x86.rs b/vendor/compiler_builtins/src/x86.rs
new file mode 100644
index 000000000..fd1f32e3a
--- /dev/null
+++ b/vendor/compiler_builtins/src/x86.rs
@@ -0,0 +1,85 @@
+#![allow(unused_imports)]
+
+use core::intrinsics;
+
+// NOTE These functions are implemented using assembly because they using a custom
+// calling convention which can't be implemented using a normal Rust function
+
+// NOTE These functions are never mangled as they are not tested against compiler-rt
+// and mangling ___chkstk would break the `jmp ___chkstk` instruction in __alloca
+
+intrinsics! {
+    #[naked]
+    #[cfg(all(
+        windows,
+        target_env = "gnu",
+        not(feature = "no-asm")
+    ))]
+    pub unsafe extern "C" fn ___chkstk_ms() {
+        core::arch::asm!(
+            "push   %ecx",
+            "push   %eax",
+            "cmp    $0x1000,%eax",
+            "lea    12(%esp),%ecx",
+            "jb     1f",
+            "2:",
+            "sub    $0x1000,%ecx",
+            "test   %ecx,(%ecx)",
+            "sub    $0x1000,%eax",
+            "cmp    $0x1000,%eax",
+            "ja     2b",
+            "1:",
+            "sub    %eax,%ecx",
+            "test   %ecx,(%ecx)",
+            "pop    %eax",
+            "pop    %ecx",
+            "ret",
+            options(noreturn, att_syntax)
+        );
+    }
+
+    // FIXME: __alloca should be an alias to __chkstk
+    #[naked]
+    #[cfg(all(
+        windows,
+        target_env = "gnu",
+        not(feature = "no-asm")
+    ))]
+    pub unsafe extern "C" fn __alloca() {
+        core::arch::asm!(
+            "jmp ___chkstk", // Jump to ___chkstk since fallthrough may be unreliable"
+            options(noreturn, att_syntax)
+        );
+    }
+
+    #[naked]
+    #[cfg(all(
+        windows,
+        target_env = "gnu",
+        not(feature = "no-asm")
+    ))]
+    pub unsafe extern "C" fn ___chkstk() {
+        core::arch::asm!(
+            "push   %ecx",
+            "cmp    $0x1000,%eax",
+            "lea    8(%esp),%ecx", // esp before calling this routine -> ecx
+            "jb     1f",
+            "2:",
+            "sub    $0x1000,%ecx",
+            "test   %ecx,(%ecx)",
+            "sub    $0x1000,%eax",
+            "cmp    $0x1000,%eax",
+            "ja     2b",
+            "1:",
+            "sub    %eax,%ecx",
+            "test   %ecx,(%ecx)",
+            "lea    4(%esp),%eax",  // load pointer to the return address into eax
+            "mov    %ecx,%esp",     // install the new top of stack pointer into esp
+            "mov    -4(%eax),%ecx", // restore ecx
+            "push   (%eax)",        // push return address onto the stack
+            "sub    %esp,%eax",     // restore the original value in eax
+            "ret",
+            options(noreturn, att_syntax)
+        );
+    }
+}