extend.texi: Clarify use of __attribute__((naked)).

gcc/

2008-05-23  Paul Brook  <paul@codesourcery.com>
	    Carlos O'Donell  <carlos@codesourcery.com>

	* doc/extend.texi: Clarify use of __attribute__((naked)).
	* doc/tm.texi: Document TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS.
	* target.h (gcc_target): Add allocate_stack_slots_for_args.
	* function.c (use_register_for_decl): Use
	targetm.calls.allocate_stack_slots_for_args.
	* target-def.h (TARGET_CALLS): Add 
	TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS.
	* config/arm/arm.c (arm_allocate_stack_slots_for_args): 
	New function.
	(TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS): Define.

gcc/testsuite/

2008-05-23  Paul Brook  <paul@codesourcery.com>
	    Carlos O'Donell  <carlos@codesourcery.com>

	* gcc.target/arm/naked-1.c: New test.
	* gcc.target/arm/naked-2.c: New test.


Co-Authored-By: Carlos O'Donell <carlos@codesourcery.com>

From-SVN: r135831

10 files changed, 86 insertions, 2 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 25e09df9add..c1712af05eb 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,17 @@
+2008-05-23  Paul Brook  <paul@codesourcery.com>
+	    Carlos O'Donell  <carlos@codesourcery.com>
+
+	* doc/extend.texi: Clarify use of __attribute__((naked)).
+	* doc/tm.texi: Document TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS.
+	* target.h (gcc_target): Add allocate_stack_slots_for_args.
+	* function.c (use_register_for_decl): Use
+	targetm.calls.allocate_stack_slots_for_args.
+	* target-def.h (TARGET_CALLS): Add 
+	TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS.
+	* config/arm/arm.c (arm_allocate_stack_slots_for_args): 
+	New function.
+	(TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS): Define.
+
 2008-05-23  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* expr.c (highest_pow2_factor) <BIT_AND_EXPR>: New case.
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 1c7002b8be4..38d4a2d9d9f 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -189,6 +189,7 @@ static bool arm_cannot_copy_insn_p (rtx);
 static bool arm_tls_symbol_p (rtx x);
 static int arm_issue_rate (void);
 static void arm_output_dwarf_dtprel (FILE *, int, rtx) ATTRIBUTE_UNUSED;
+static bool arm_allocate_stack_slots_for_args (void);
 
 
 /* Initialize the GCC target structure.  */
@@ -289,6 +290,9 @@ static void arm_output_dwarf_dtprel (FILE *, int, rtx) ATTRIBUTE_UNUSED;
 #undef  TARGET_SETUP_INCOMING_VARARGS
 #define TARGET_SETUP_INCOMING_VARARGS arm_setup_incoming_varargs
 
+#undef TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS
+#define TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS arm_allocate_stack_slots_for_args
+
 #undef TARGET_DEFAULT_SHORT_ENUMS
 #define TARGET_DEFAULT_SHORT_ENUMS arm_default_short_enums
 
@@ -1619,6 +1623,14 @@ arm_current_func_type (void)
 
   return cfun->machine->func_type;
 }
+
+bool
+arm_allocate_stack_slots_for_args (void)
+{
+  /* Naked functions should not allocate stack slots for arguments.  */
+  return !IS_NAKED (arm_current_func_type ());
+}
+
 
 /* Return 1 if it is possible to return using a single instruction.
    If SIBLING is non-null, this is a test for a return before a sibling
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 78d581d62e6..f0e85933699 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -2512,7 +2512,13 @@ defined by shared libraries.
 @cindex function without a prologue/epilogue code
 Use this attribute on the ARM, AVR, IP2K and SPU ports to indicate that
 the specified function does not need prologue/epilogue sequences generated by
-the compiler.  It is up to the programmer to provide these sequences.
+the compiler.  It is up to the programmer to provide these sequences. The 
+only statements that can be safely included in naked functions are 
+@code{asm} statements that do not have operands.  All other statements,
+including declarations of local variables, @code{if} statements, and so 
+forth, should be avoided.  Naked functions should be used to implement the 
+body of an assembly function, while allowing the compiler to construct
+the requisite function declaration for the assembler.
 
 @item near
 @cindex functions which do not handle memory bank switching on 68HC11/68HC12
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 12a2740173b..8c0de3b41de 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -10465,3 +10465,14 @@ to the functions in @file{libgcc} that provide low-level support for
 call stack unwinding.  It is used in declarations in @file{unwind-generic.h}
 and the associated definitions of those functions.
 @end defmac
+
+@deftypefn {Target Hook} {bool} TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS (void)
+When optimization is disabled, this hook indicates whether or not
+arguments should be allocated to stack slots.  Normally, GCC allocates
+stacks slots for arguments when not optimizing in order to make
+debugging easier.  However, when a function is declared with
+@code{__attribute__((naked))}, there is no stack frame, and the compiler
+cannot safely move arguments from the registers in which they are passed
+to the stack.  Therefore, this hook should return true in general, but
+false for naked functions.  The default implementation always returns true.
+@end deftypefn
diff --git a/gcc/function.c b/gcc/function.c
index 29d4c1eda6e..5f9c3a5ce2c 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -1776,6 +1776,9 @@ aggregate_value_p (const_tree exp, const_tree fntype)
 bool
 use_register_for_decl (const_tree decl)
 {
+  if (!targetm.calls.allocate_stack_slots_for_args())
+    return true;
+  
   /* Honor volatile.  */
   if (TREE_SIDE_EFFECTS (decl))
     return false;
diff --git a/gcc/target-def.h b/gcc/target-def.h
index c4bc6962a61..19e882f3787 100644
--- a/gcc/target-def.h
+++ b/gcc/target-def.h
@@ -568,6 +568,7 @@
 
 #define TARGET_FUNCTION_VALUE default_function_value
 #define TARGET_INTERNAL_ARG_POINTER default_internal_arg_pointer
+#define TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS hook_bool_void_true
 
 #define TARGET_CALLS {						\
    TARGET_PROMOTE_FUNCTION_ARGS,				\
@@ -587,7 +588,8 @@
    TARGET_ARG_PARTIAL_BYTES,					\
    TARGET_INVALID_ARG_FOR_UNPROTOTYPED_FN,			\
    TARGET_FUNCTION_VALUE,					\
-   TARGET_INTERNAL_ARG_POINTER					\
+   TARGET_INTERNAL_ARG_POINTER,					\
+   TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS				\
    }
 
 #ifndef TARGET_UNWIND_TABLES_DEFAULT
diff --git a/gcc/target.h b/gcc/target.h
index c331020b6ab..fa85e7cacd6 100644
--- a/gcc/target.h
+++ b/gcc/target.h
@@ -830,6 +830,11 @@ struct gcc_target
     /* Return an rtx for the argument pointer incoming to the
        current function.  */
     rtx (*internal_arg_pointer) (void);
+
+    /* Return true if all function parameters should be spilled to the
+       stack.  */
+    bool (*allocate_stack_slots_for_args) (void);
+    
   } calls;
 
   /* Return the diagnostic message string if conversion from FROMTYPE
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index d18afd8e6aa..1c457cc7fa3 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2008-05-23  Paul Brook  <paul@codesourcery.com>
+	    Carlos O'Donell  <carlos@codesourcery.com>
+
+	* gcc.target/arm/naked-1.c: New test.
+	* gcc.target/arm/naked-2.c: New test.
+
 2008-05-23  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/36314
diff --git a/gcc/testsuite/gcc.target/arm/naked-1.c b/gcc/testsuite/gcc.target/arm/naked-1.c
new file mode 100644
index 00000000000..8f9ff711a5e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/naked-1.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+/* Check that function arguments aren't assigned and copied to stack slots
+   in naked functions.  This ususally happens at -O0 (presumably for
+   better debugging), but is highly undesirable if we haven't created
+   a stack frame.  */
+void __attribute__((naked))
+foo(int n)
+{
+  __asm__ volatile ("frob r0\n");
+}
+/* { dg-final { scan-assembler "\tfrob r0" } } */
+/* { dg-final { scan-assembler-not "\tstr" } } */
diff --git a/gcc/testsuite/gcc.target/arm/naked-2.c b/gcc/testsuite/gcc.target/arm/naked-2.c
new file mode 100644
index 00000000000..92e7db4447d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/naked-2.c
@@ -0,0 +1,12 @@
+/* Verify that __attribute__((naked)) produces a naked function 
+   that does not use bx to return. Naked functions could be used
+   to implement interrupt routines and must not return using bx.  */
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+/* Use more arguments than we have argument registers.  */
+int __attribute__((naked)) foo(int a, int b, int c, int d, int e, int f)
+{
+  __asm__ volatile ("@ naked");
+}
+/* { dg-final { scan-assembler "\t@ naked" } } */
+/* { dg-final { scan-assembler-not "\tbx\tlr" } } */