s390.c (struct s390_frame_layout): New struct as element of struct machine_function.

2004-08-12  Andreas Krebbel  <krebbel1@de.ibm.com>

	* config/s390/s390.c (struct s390_frame_layout): New struct as element
	of struct machine_function.
	(cfun->machine->frame_size): Moved into cfun->machine->frame_layout and
	changed all uses.
	(cfun->machine->save_fprs_p): Replaced by cfun_save_high_fprs and
	changed all uses.
	(cfun_frame_layout, cfun_save_high_fprs_p, cfun_gprs_save_area_size)
	(cfun_set_fpr_bit, cfun_fpr_bit_p): New macros.
	(s390_frame_area, s390_register_info): New functions.
	(s390_optimize_prolog): Renamed to s390_optimize_prologue.  Added check
	for base register.
	(s390_return_addr_rtx, s390_return_address_offset)
	(s390_va_start, s390_gimplify_va_arg)
	(s390_emit_prologue, s390_emit_epilogue): Adjusted for new stack
	layouts.
	(s390_frame_info): Functionality partly moved to s390_register_info.
	Made adaptions for new stack layout.
	(save_gprs, restore_gprs): Changed meaning of second parameter and
	adapted all callers.

	* config/s390/s390.h (s390_backchain_string): New global variable.
	(MASK_BACKCHAIN): Removed definition.
	(TARGET_BACKCHAIN): Changed check.
	(TARGET_KERNEL_BACKCHAIN): New macro.
	(TARGET_SWITCHES): Removed entries of "backchain" and "no-backchain".
	(TARGET_OPTIONS): Added "backchain", "no-backchain" and
	"kernel-backchain".
	(DYNAMIC_CHAIN_ADDRESS): Adjusted for new stack layouts.

	* config/s390/s390.md ("allocate_stack"): Added TARGET_KERNEL_BACKCHAIN
	as condition.  Adjusted for new stack layout.

	* doc/invoke.texi: Added documentation for new option
	"-mkernel-backchain" and adjusted documentation of "-mbackchain" and
	"-mno-backchain".

From-SVN: r85882

gcc/ChangeLog

+2004-08-12  Andreas Krebbel  <krebbel1@de.ibm.com>
+
+	* config/s390/s390.c (struct s390_frame_layout): New struct as element
+	of struct machine_function.
+	(cfun->machine->frame_size): Moved into cfun->machine->frame_layout and
+	changed all uses.
+	(cfun->machine->save_fprs_p): Replaced by cfun_save_high_fprs and
+	changed all uses.
+	(cfun_frame_layout, cfun_save_high_fprs_p, cfun_gprs_save_area_size)
+	(cfun_set_fpr_bit, cfun_fpr_bit_p): New macros.
+	(s390_frame_area, s390_register_info): New functions.
+	(s390_optimize_prolog): Renamed to s390_optimize_prologue.  Added check
+	for base register.
+	(s390_return_addr_rtx, s390_return_address_offset)
+	(s390_va_start, s390_gimplify_va_arg)
+	(s390_emit_prologue, s390_emit_epilogue): Adjusted for new stack
+	layouts.
+	(s390_frame_info): Functionality partly moved to s390_register_info.
+	Made adaptions for new stack layout.
+	(save_gprs, restore_gprs): Changed meaning of second parameter and
+	adapted all callers.
+
+	* config/s390/s390.h (s390_backchain_string): New global variable.
+	(MASK_BACKCHAIN): Removed definition.
+	(TARGET_BACKCHAIN): Changed check.
+	(TARGET_KERNEL_BACKCHAIN): New macro.
+	(TARGET_SWITCHES): Removed entries of "backchain" and "no-backchain".
+	(TARGET_OPTIONS): Added "backchain", "no-backchain" and
+	"kernel-backchain".
+	(DYNAMIC_CHAIN_ADDRESS): Adjusted for new stack layouts.
+
+	* config/s390/s390.md ("allocate_stack"): Added TARGET_KERNEL_BACKCHAIN
+	as condition.  Adjusted for new stack layout.
+
+	* doc/invoke.texi: Added documentation for new option
+	"-mkernel-backchain" and adjusted documentation of "-mbackchain" and
+	"-mno-backchain".
+
 2004-08-12  Paul Brook  <paul@codesourcery.com>
 
 	* config/arm/lib1funcs.asm (ARM_FUNC_ALIAS): Also alias _L__name.

gcc/config/s390/s390.h

@@ -60,6 +60,8 @@ extern enum processor_type s390_arch;
 extern enum processor_flags s390_arch_flags;
 extern const char *s390_arch_string;
 
+extern const char *s390_backchain_string;
+
 #define TARGET_CPU_IEEE_FLOAT \
 	(s390_arch_flags & PF_IEEE_FLOAT)
 #define TARGET_CPU_ZARCH \
@@ -89,7 +91,6 @@ extern const char *s390_arch_string;
 extern int target_flags;
 
 #define MASK_HARD_FLOAT            0x01
-#define MASK_BACKCHAIN             0x02
 #define MASK_SMALL_EXEC            0x04
 #define MASK_DEBUG_ARG             0x08
 #define MASK_64BIT                 0x10
@@ -100,7 +101,6 @@ extern int target_flags;
 
 #define TARGET_HARD_FLOAT          (target_flags & MASK_HARD_FLOAT)
 #define TARGET_SOFT_FLOAT          (!(target_flags & MASK_HARD_FLOAT))
-#define TARGET_BACKCHAIN           (target_flags & MASK_BACKCHAIN)
 #define TARGET_SMALL_EXEC          (target_flags & MASK_SMALL_EXEC)
 #define TARGET_DEBUG_ARG           (target_flags & MASK_DEBUG_ARG)
 #define TARGET_64BIT               (target_flags & MASK_64BIT)
@@ -110,6 +110,9 @@ extern int target_flags;
 #define TARGET_NO_FUSED_MADD       (target_flags & MASK_NO_FUSED_MADD)
 #define TARGET_FUSED_MADD	   (! TARGET_NO_FUSED_MADD)
 
+#define TARGET_BACKCHAIN           (s390_backchain_string[0] == '1')
+#define TARGET_KERNEL_BACKCHAIN    (s390_backchain_string[0] == '2')
+
 /* ??? Once this actually works, it could be made a runtime option.  */
 #define TARGET_IBM_FLOAT           0
 #define TARGET_IEEE_FLOAT          1
@@ -123,8 +126,6 @@ extern int target_flags;
 #define TARGET_SWITCHES                                                  \
 { { "hard-float",      1, N_("Use hardware fp")},                        \
   { "soft-float",     -1, N_("Don't use hardware fp")},                  \
-  { "backchain",       2, N_("Set backchain")},                          \
-  { "no-backchain",   -2, N_("Don't set backchain (faster, but debug harder")},\
   { "small-exec",      4, N_("Use bras for executable < 64k")},          \
   { "no-small-exec",  -4, N_("Don't use bras")},                         \
   { "debug",           8, N_("Additional debug prints")},                \
@@ -146,6 +147,12 @@ extern int target_flags;
     N_("Schedule code for given CPU"), 0},                      \
   { "arch=",            &s390_arch_string,                      \
     N_("Generate code for given CPU"), 0},                      \
+  { "backchain",        &s390_backchain_string,                 \
+    N_("Set backchain"), "1"},                                  \
+  { "no-backchain",     &s390_backchain_string,                 \
+    N_("Do not set backchain"), ""},                            \
+  { "kernel-backchain", &s390_backchain_string,                 \
+    N_("Set backchain appropriate for the linux kernel"), "2"}, \
 }
 
 /* Support for configure-time defaults.  */
@@ -559,9 +566,13 @@ extern int current_function_outgoing_args_size;
    For frames farther back, we use the stack slot where
    the corresponding RETURN_REGNUM register was saved.  */
 
-#define DYNAMIC_CHAIN_ADDRESS(FRAME)						\
-  ((FRAME) != hard_frame_pointer_rtx ? (FRAME) :				\
-   plus_constant (arg_pointer_rtx, -STACK_POINTER_OFFSET))
+#define DYNAMIC_CHAIN_ADDRESS(FRAME)                                            \
+  (TARGET_BACKCHAIN ?                                                           \
+   ((FRAME) != hard_frame_pointer_rtx ? (FRAME) :				\
+    plus_constant (arg_pointer_rtx, -STACK_POINTER_OFFSET)) :                   \
+    ((FRAME) != hard_frame_pointer_rtx ?                                        \
+     plus_constant ((FRAME), STACK_POINTER_OFFSET - UNITS_PER_WORD) :           \
+     plus_constant (arg_pointer_rtx, -UNITS_PER_WORD)))
 
 #define RETURN_ADDR_RTX(COUNT, FRAME)						\
   s390_return_addr_rtx ((COUNT), DYNAMIC_CHAIN_ADDRESS ((FRAME)))

gcc/config/s390/s390.md

@@ -7217,11 +7217,19 @@
         (plus (reg 15) (match_operand 1 "general_operand" "")))
    (set (match_operand 0 "general_operand" "")
         (reg 15))]
- "TARGET_BACKCHAIN"
+ "TARGET_BACKCHAIN || TARGET_KERNEL_BACKCHAIN"
 {
     rtx stack = gen_rtx_REG (Pmode, STACK_POINTER_REGNUM);
-    rtx chain = gen_rtx_MEM (Pmode, stack);
-    rtx temp = gen_reg_rtx (Pmode);
+    rtx chain;
+    rtx temp;
+
+    if (TARGET_KERNEL_BACKCHAIN)
+      chain = plus_constant (stack, STACK_POINTER_OFFSET - UNITS_PER_WORD);
+    else
+      chain = stack;
+
+    chain = gen_rtx_MEM (Pmode, chain);
+    temp = gen_reg_rtx (Pmode);
 
     emit_move_insn (temp, chain);
 

gcc/doc/invoke.texi

@@ -617,7 +617,7 @@ See RS/6000 and PowerPC Options.
 
 @emph{S/390 and zSeries Options}
 @gccoptlist{-mtune=@var{cpu-type}  -march=@var{cpu-type} @gol
--mhard-float  -msoft-float  -mbackchain  -mno-backchain @gol
+-mhard-float  -msoft-float  -mbackchain  -mno-backchain -mkernel-backchain @gol
 -msmall-exec  -mno-small-exec  -mmvcle -mno-mvcle @gol
 -m64  -m31  -mdebug  -mno-debug  -mesa  -mzarch @gol
 -mtpf-trace -mno-tpf-trace  -mfused-madd  -mno-fused-madd}
@@ -10454,13 +10454,27 @@ generates IEEE floating-point instructions.  This is the default.
 
 @item -mbackchain
 @itemx -mno-backchain
+@itemx -mkernel-backchain
 @opindex mbackchain
 @opindex mno-backchain
-Generate (or do not generate) code which maintains an explicit
-backchain within the stack frame that points to the caller's frame.
-This may be needed to allow debugging using tools that do not understand
-DWARF-2 call frame information.  The default is not to generate the
-backchain.
+@opindex mkernel-backchain
+In order to provide a backchain the address of the caller's frame
+is stored within the callee's stack frame.
+A backchain may be needed to allow debugging using tools that do not understand
+DWARF-2 call frame information.
+For @option{-mno-backchain} no backchain is maintained at all which is the 
+default. 
+If one of the other options is present the backchain pointer is placed either 
+on top of the stack frame  (@option{-mkernel-backchain}) or on
+the bottom (@option{-mbackchain}).
+Beside the different backchain location @option{-mkernel-backchain}
+also changes stack frame layout breaking the ABI. This option
+is intended to be used for code which internally needs a backchain but has
+to get by with a limited stack size e.g. the linux kernel. 
+Internal unwinding code not using DWARF-2 info has to be able to locate the
+return address of a function. That will be eased be the fact that
+the return address of a function is placed two words below the backchain 
+pointer.
 
 @item -msmall-exec
 @itemx -mno-small-exec