Fix support for Linux/S390 zSeries

platform/switch_s390_unix.h

@@ -2,6 +2,11 @@
  * this is the internal transfer function.
  *
  * HISTORY
+ * 25-Jan-12  Alexey Borzenkov <[email protected]>
+ *      Fixed Linux/S390 port to work correctly with
+ *      different optimization options both on 31-bit
+ *      and 64-bit. Thanks to Stefan Raabe for lots
+ *      of testing.
  * 24-Nov-02  Christian Tismer  <[email protected]>
  *      needed to add another magic constant to insure
  *      that f in slp_eval_frame(PyFrameObject *f)
@@ -15,24 +20,50 @@
 
 #ifdef SLP_EVAL
 
-#define STACK_MAGIC 0
+#ifdef __s390x__
+#define STACK_MAGIC 20 /* 20 * 8 = 160 bytes of function call area */
+#else
+#define STACK_MAGIC 24 /* 24 * 4 = 96 bytes of function call area */
+#endif
 
-#define REGS_TO_SAVE "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r14", \
+/* Technically, r11-r13 also need saving, but function prolog starts
+   with stm(g) and since there are so many saved registers already
+   it won't be optimized, resulting in all r6-r15 being saved */
+#define REGS_TO_SAVE "r6", "r7", "r8", "r9", "r10", "r14", \
 		     "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7", \
 		     "f8", "f9", "f10", "f11", "f12", "f13", "f14", "f15"
 
 static int
 slp_switch(void)
 {
-    register int *stackref, stsizediff;
+    register long *stackref, stsizediff;
     __asm__ volatile ("" : : : REGS_TO_SAVE);
-    __asm__ ("lr %0, 15" : "=g" (stackref) : );
+#ifdef __s390x__
+    __asm__ volatile ("lgr %0, 15" : "=r" (stackref) : );
+#else
+    __asm__ volatile ("lr %0, 15" : "=r" (stackref) : );
+#endif
     {
         SLP_SAVE_STATE(stackref, stsizediff);
+/* N.B.
+   r11 may be used as the frame pointer, and in that case it cannot be
+   clobbered and needs offsetting just like the stack pointer (but in cases
+   where frame pointer isn't used we might clobber it accidentally). What's
+   scary is that r11 is 2nd (and even 1st when GOT is used) callee saved
+   register that gcc would chose for surviving function calls. However,
+   since r6-r10 are clobbered above, their cost for reuse is reduced, so
+   gcc IRA will chose them over r11 (not seeing r11 is implicitly saved),
+   making it relatively safe to offset in all cases. :) */
         __asm__ volatile (
-            "ar 15, %0"
+#ifdef __s390x__
+            "agr 15, %0\n\t"
+            "agr 11, %0"
+#else
+            "ar 15, %0\n\t"
+            "ar 11, %0"
+#endif
             : /* no outputs */
-            : "g" (stsizediff)
+            : "r" (stsizediff)
             );
         SLP_RESTORE_STATE();
     }

slp_platformselect.h

@@ -25,7 +25,7 @@
 #elif defined(__GNUC__) && defined(__s390__) && defined(__linux__)
 #include "platform/switch_s390_unix.h"	/* Linux/S390 */
 #elif defined(__GNUC__) && defined(__s390x__) && defined(__linux__)
-#include "platform/switch_s390_unix.h"	/* Linux/S390 zSeries (identical) */
+#include "platform/switch_s390_unix.h"	/* Linux/S390 zSeries (64-bit) */
 #elif defined(__GNUC__) && defined(__arm__)
 #include "platform/switch_arm32_gcc.h" /* gcc using arm32 */
 #elif defined(__GNUC__) && defined(__mips__) && defined(__linux__)