0From: Alexandre Oliva <oliva@adacore.com>

strub: introduce STACK_ADDRESS_OFFSET

Since STACK_POINTER_OFFSET is not necessarily at the boundary between
caller- and callee-owned stack, as desired by
__builtin_stack_address(), and using it as if it were or not causes
problems, introduce a new macro so that ports can define it suitably,
without modifying STACK_POINTER_OFFSET.

for  gcc/ChangeLog

	PR middle-end/112917
	PR middle-end/113100
	* builtins.cc (expand_builtin_stack_address): Use
	STACK_ADDRESS_OFFSET.
	* doc/extend.texi (__builtin_stack_address): Adjust.
	* config/sparc/sparc.h (STACK_ADDRESS_OFFSET): Define.
	* doc/tm.texi.in (STACK_ADDRESS_OFFSET): Document.
	* doc/tm.texi: Rebuilt.

diff --git a/gcc/builtins.cc b/gcc/builtins.cc
index a0bd82c7981c05caf2764de70c62fe83bef9ad29..1d54ea0a83200f0c7d237997d19605b988139115 100644 (file)
--- a/gcc/builtins.cc
+++ b/gcc/builtins.cc
@@ -5450,7 +5450,7 @@ expand_builtin_stack_address ()
   rtx ret = convert_to_mode (ptr_mode, copy_to_reg (stack_pointer_rtx),
                             STACK_UNSIGNED);
 
-#ifdef SPARC_STACK_BOUNDARY_HACK
+#ifdef STACK_ADDRESS_OFFSET
   /* Unbias the stack pointer, bringing it to the boundary between the
      stack area claimed by the active function calling this builtin,
      and stack ranges that could get clobbered if it called another
@@ -5477,8 +5477,7 @@ expand_builtin_stack_address ()
      (caller) function's active area as well, whereas those pushed or
      allocated temporarily for a call are regarded as part of the
      callee's stack range, rather than the caller's.  */
-  if (SPARC_STACK_BOUNDARY_HACK)
-    ret = plus_constant (ptr_mode, ret, STACK_POINTER_OFFSET);
+  ret = plus_constant (ptr_mode, ret, STACK_ADDRESS_OFFSET);
 #endif
 
   return force_reg (ptr_mode, ret);

diff --git a/gcc/config/sparc/sparc.h b/gcc/config/sparc/sparc.h
index fc064a92c22d91369da74004f8061608f9635ca2..fb074808d30d4b5a049b429e7a732137728e5a5e 100644 (file)
--- a/gcc/config/sparc/sparc.h
+++ b/gcc/config/sparc/sparc.h
@@ -734,6 +734,13 @@ along with GCC; see the file COPYING3.  If not see
      parameter regs.  */
 #define STACK_POINTER_OFFSET (FIRST_PARM_OFFSET(0) + SPARC_STACK_BIAS)
 
+/* Unbias the stack pointer if needed, and move past the register save area,
+   that is never in use while a function is active, so that it is regarded as a
+   callee save area rather than as part of the function's own stack area.  This
+   enables __strub_leave() to do a better job of clearing the stack frame of a
+   previously-called sibling.  */
+#define STACK_ADDRESS_OFFSET STACK_POINTER_OFFSET
+
 /* Base register for access to local variables of the function.  */
 #define HARD_FRAME_POINTER_REGNUM 30
 

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index f0d02c9d42398b3f456c7241746badc431832a1a..142e41ab8fbfeaa9fde71cefc7559138bf549362 100644 (file)
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -12799,7 +12799,7 @@ situations.
 
 @deftypefn {Built-in Function} {void *} __builtin_stack_address ()
 This function returns the stack pointer register, offset by
-@code{STACK_POINTER_OFFSET}.
+@code{STACK_ADDRESS_OFFSET} if that's defined.
 
 Conceptually, the returned address returned by this built-in function is
 the boundary between the stack area allocated for use by its caller, and

diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 69ae63c77de6e67e197fb40d8d5ccb2dbd42c2d0..c8b8b126b2424b6552f824ba42ac329cfaf84d84 100644 (file)
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -3456,6 +3456,35 @@ or type, otherwise return false.  The default implementation always returns
 true.
 @end deftypefn
 
+@defmac STACK_ADDRESS_OFFSET
+Offset from the stack pointer register to the boundary address between
+the stack area claimed by an active function, and stack ranges that
+could get clobbered if it called another function.  It should NOT
+encompass any stack red zone, that is used in leaf functions.
+
+This value is added to the stack pointer register to compute the address
+returned by @code{__builtin_stack_address}, and this is its only use.
+If this macro is not defined, no offset is added.  Defining it like
+@code{STACK_POINTER_OFFSET} may be appropriate for many machines, but
+not all.
+
+On SPARC, for example, the register save area is *not* considered active
+or used by the active function, but rather as akin to the area in which
+call-preserved registers are saved by callees, so the stack address is
+above that area, even though the (unbiased) stack pointer points below
+it.  This enables @code{__strub_leave} to clear what would otherwise
+overlap with its own register save area.
+
+On PowerPC, @code{STACK_POINTER_OFFSET} also reserves space for a save
+area, but that area is used by the caller rather than the callee, so the
+boundary address is below it.
+
+If the address is computed too high or too low, parts of a stack range
+that should be scrubbed may be left unscrubbed, scrubbing may corrupt
+active portions of the stack frame, and stack ranges may be
+doubly-scrubbed by caller and callee.
+@end defmac
+
 @defmac TARGET_STRUB_USE_DYNAMIC_ARRAY
 If defined to nonzero, @code{__strub_leave} will allocate a dynamic
 array covering the stack range that needs scrubbing before clearing it.

diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 21343d4d1bf2fcee804e1365e985b4fa4fa7f066..658e1e63371e5ddba6e39ffde6b6d9b995eec473 100644 (file)
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -2688,6 +2688,35 @@ may reduce the size of debug information on some ports.
 
 @hook TARGET_HAVE_STRUB_SUPPORT_FOR
 
+@defmac STACK_ADDRESS_OFFSET
+Offset from the stack pointer register to the boundary address between
+the stack area claimed by an active function, and stack ranges that
+could get clobbered if it called another function.  It should NOT
+encompass any stack red zone, that is used in leaf functions.
+
+This value is added to the stack pointer register to compute the address
+returned by @code{__builtin_stack_address}, and this is its only use.
+If this macro is not defined, no offset is added.  Defining it like
+@code{STACK_POINTER_OFFSET} may be appropriate for many machines, but
+not all.
+
+On SPARC, for example, the register save area is *not* considered active
+or used by the active function, but rather as akin to the area in which
+call-preserved registers are saved by callees, so the stack address is
+above that area, even though the (unbiased) stack pointer points below
+it.  This enables @code{__strub_leave} to clear what would otherwise
+overlap with its own register save area.
+
+On PowerPC, @code{STACK_POINTER_OFFSET} also reserves space for a save
+area, but that area is used by the caller rather than the callee, so the
+boundary address is below it.
+
+If the address is computed too high or too low, parts of a stack range
+that should be scrubbed may be left unscrubbed, scrubbing may corrupt
+active portions of the stack frame, and stack ranges may be
+doubly-scrubbed by caller and callee.
+@end defmac
+
 @defmac TARGET_STRUB_USE_DYNAMIC_ARRAY
 If defined to nonzero, @code{__strub_leave} will allocate a dynamic
 array covering the stack range that needs scrubbing before clearing it.