rt: Remove check_stack_alignment

This function does not do what it tries to do and it is expensive

Author: brson

src/rt/arch/i386/record_sp.S

@@ -4,18 +4,15 @@
 #define RECORD_SP_LIMIT    _record_sp_limit
 #define GET_SP_LIMIT       _get_sp_limit
 #define GET_SP             _get_sp
-#define CHECK_STACK        _check_stack_alignment
 #else
 #define RECORD_SP_LIMIT    record_sp_limit
 #define GET_SP_LIMIT       get_sp_limit
 #define GET_SP             get_sp
-#define CHECK_STACK        check_stack_alignment
 #endif
 
 .globl RECORD_SP_LIMIT
 .globl GET_SP_LIMIT
 .globl GET_SP
-.globl CHECK_STACK
 
 #if defined(__linux__) || defined(__FreeBSD__)
 RECORD_SP_LIMIT:
@@ -61,10 +58,3 @@ GET_SP_LIMIT:
 GET_SP:
 	movl %esp, %eax
 	ret
-
-// This will segfault if not called on a 16-byte boundary
-CHECK_STACK:
-	subl $28, %esp
-	movaps %xmm0, (%esp)
-	addl $28, %esp
-	ret

src/rt/arch/x86_64/record_sp.S

@@ -4,18 +4,15 @@
 #define RECORD_SP_LIMIT    _record_sp_limit
 #define GET_SP_LIMIT       _get_sp_limit
 #define GET_SP             _get_sp
-#define CHECK_STACK        _check_stack_alignment
 #else
 #define RECORD_SP_LIMIT    record_sp_limit
 #define GET_SP_LIMIT       get_sp_limit
 #define GET_SP             get_sp
-#define CHECK_STACK        check_stack_alignment
 #endif
 
 .globl RECORD_SP_LIMIT
 .globl GET_SP_LIMIT
 .globl GET_SP
-.globl CHECK_STACK
 
 #if defined(__linux__)
 RECORD_SP_LIMIT:
@@ -53,10 +50,3 @@ GET_SP_LIMIT:
 GET_SP:
 	movq %rsp, %rax
 	ret
-
-// This will segfault if not called on a 16-byte boundary
-CHECK_STACK:
-	subq $24, %rsp
-	movaps %xmm0, (%rsp)
-	addq $24, %rsp
-	ret

src/rt/rust_upcall.cpp

@@ -28,24 +28,10 @@
         (task)->name, (task));
 #endif
 
-// This is called to ensure we've set up our rust stacks
-// correctly. Strategically placed at entry to upcalls because they begin on
-// the rust stack and happen frequently enough to catch most stack changes,
-// including at the beginning of all landing pads.
-// FIXME: Enable this for windows
-#if (defined __linux__ || defined __APPLE__ || defined __FreeBSD__) \
-    && (defined(GCC_VERSION) && GCC_VERSION > 40300)
-extern "C" void
-check_stack_alignment() __attribute__ ((aligned (16)));
-#else
-static void check_stack_alignment() { }
-#endif
-
 #define UPCALL_SWITCH_STACK(A, F) call_upcall_on_c_stack((void*)A, (void*)F)
 
 inline void
 call_upcall_on_c_stack(void *args, void *fn_ptr) {
-    check_stack_alignment();
     rust_task *task = rust_get_current_task();
     task->call_on_c_stack(args, fn_ptr);
 }