From 1442df6958023d8cb264a9aceaec883ededfd77d Mon Sep 17 00:00:00 2001
From: Gareth Rees <gdr@ravenbrook.com>
Date: Wed, 5 Jun 2019 10:36:50 +0100
Subject: [PATCH] Revert change 196178, submitted on wrong branch.

Copied from Perforce
 Change: 196185
---
 mps/code/ss.h | 65 ++++++++++++++-------------------------------------
 1 file changed, 17 insertions(+), 48 deletions(-)

diff --git a/mps/code/ss.h b/mps/code/ss.h
index 513b4e73237..59543ae7048 100644
--- a/mps/code/ss.h
+++ b/mps/code/ss.h
@@ -1,7 +1,7 @@
 /* ss.h: STACK SCANNING
  *
  * $Id$
- * Copyright (c) 2001-2019 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2001-2018 Ravenbrook Limited.  See end of file for license.
  *
  * This module saves the mutator context on entry to the MPS, and
  * provides functions for decoding the context and scanning the root
@@ -13,12 +13,21 @@
 
 #include "mpm.h"
 
-
-/* StackContext -- some of the mutator's state */
-
-typedef struct StackContextStruct StackContextStruct;
-
      
+/* StackContext -- some of the mutator's state
+ *
+ * The jumpBuffer is used to capture most of the mutator's state on
+ * entry to the MPS, but can't capture it all.  See
+ * <design/stack-scan#.sol.setjmp.scan>.
+ */
+
+#include <setjmp.h>
+
+typedef struct StackContextStruct {
+  jmp_buf jumpBuffer;
+} StackContextStruct;
+
+
 /* StackHot -- capture a hot stack pointer
  *
  * Sets *stackOut to a stack pointer that includes the current frame.
@@ -50,44 +59,6 @@ void StackHot(void **stackOut);
 
 /* STACK_CONTEXT_SAVE -- save the callee-saves and stack pointer */
 
-#if (defined(MPS_OS_FR) || defined(MPS_OS_LI)) && defined(MPS_ARCH_I3)
-
-struct StackContextStruct {
-  Word calleeSave[4];
-};
-
-#define STACK_CONTEXT_SAVE(sc)                                       \
-  BEGIN                                                              \
-    __asm__ volatile ("mov %%ebx, %0" : "=m" ((sc)->calleeSave[0])); \
-    __asm__ volatile ("mov %%esi, %0" : "=m" ((sc)->calleeSave[1])); \
-    __asm__ volatile ("mov %%edi, %0" : "=m" ((sc)->calleeSave[2])); \
-    __asm__ volatile ("mov %%ebp, %0" : "=m" ((sc)->calleeSave[3])); \
-  END
-
-#elif (defined(MPS_OS_FR) || defined(MPS_OS_LI)) && defined(MPS_ARCH_I6)
-
-struct StackContextStruct {
-  Word calleeSave[6];
-};
-
-#define STACK_CONTEXT_SAVE(sc)                                       \
-  BEGIN                                                              \
-    __asm__ volatile ("mov %%rbp, %0" : "=m" ((sc)->calleeSave[0])); \
-    __asm__ volatile ("mov %%rbx, %0" : "=m" ((sc)->calleeSave[1])); \
-    __asm__ volatile ("mov %%r12, %0" : "=m" ((sc)->calleeSave[2])); \
-    __asm__ volatile ("mov %%r13, %0" : "=m" ((sc)->calleeSave[3])); \
-    __asm__ volatile ("mov %%r14, %0" : "=m" ((sc)->calleeSave[4])); \
-    __asm__ volatile ("mov %%r15, %0" : "=m" ((sc)->calleeSave[5])); \
-  END
-
-#else /* jmp_buf platforms */
-
-#include <setjmp.h>
-
-struct StackContextStruct {
-  jmp_buf jumpBuffer;
-};
-
 #if defined(MPS_OS_XC)
 
 /* We call _setjmp rather than setjmp because we can be confident what
@@ -103,9 +74,7 @@ struct StackContextStruct {
 
 #define STACK_CONTEXT_SAVE(sc) ((void)setjmp((sc)->jumpBuffer))
 
-#endif /* jmp_buf platforms */
-
-#endif /* platform specific code */
+#endif /* platform defines */
 
 
 /* StackScan -- scan the mutator's stack and registers
@@ -123,7 +92,7 @@ extern Res StackScan(ScanState ss, void *stackCold,
 
 /* C. COPYRIGHT AND LICENSE
  *
- * Copyright (C) 2001-2019 Ravenbrook Limited <https://www.ravenbrook.com/>.
+ * Copyright (C) 2001-2018 Ravenbrook Limited <https://www.ravenbrook.com/>.
  * All rights reserved.  This is an open source license.  Contact
  * Ravenbrook for commercial licensing options.
  *