rt: Have __morestack conform to the calling convention that LLVM generates on x86

Author: pcwalton

src/rt/arch/i386/morestack.S

@@ -8,31 +8,34 @@
 #if defined(__APPLE__) || defined(_WIN32)
 #define RUST_NEW_STACK      _rust_new_stack
 #define RUST_DEL_STACK      _rust_del_stack
+#define MORESTACK           ___morestack
 #else
 #define RUST_NEW_STACK      rust_new_stack
 #define RUST_DEL_STACK      rust_del_stack
+#define MORESTACK           __morestack
 #endif
 
 .globl RUST_NEW_STACK
 .globl RUST_DEL_STACK
 
-.globl __morestack
+.globl MORESTACK
 
-__morestack:
-    pushl %edx              // param 2: size of arguments
-    leal 8(%esp),%eax
-    pushl %eax              // param 1: starting addr of arguments
-    pushl %ecx              // param 0: amount of space needed
+MORESTACK:
+    pushl 8(%esp)           //               argsz > ra stksz argsz x x ra args
+    leal 28(%esp),%eax      //                 argsz ra stksz argsz x x ra args 
+    pushl %eax              //          argp > argsz ra stksz argsz x x ra args
+    pushl 12(%esp)          //    stksz > argp argsz ra stksz argsz x x ra args
     calll RUST_NEW_STACK
+    addl $12,%esp           //                       ra stksz argsz x x ra args
 
     movl (%esp),%edx        // Grab the return pointer.
     incl %edx               // Skip past the `ret`.
     movl %eax,%esp          // Switch to the new stack.
-    calll *%edx             // Enter the new function.
+    calll *%edx             // Re-enter the function that called us.
 
     // Now the function that called us has returned, so we need to delete the
     // old stack space.
     calll RUST_DEL_STACK
-    movl %eax,%esp          // Switch back to the old stack.
-    retl
+    movl %eax,%esp
+    retl $8                 //                       ra stksz argsz x x ra args