AVR: Provide built-ins for strlen where the string lives in some AS.

This patch adds built-in functions __builtin_avr_strlen_flash,
__builtin_avr_strlen_flashx and __builtin_avr_strlen_memx.
Purpose is that higher-level functions can use __builtin_constant_p
on strlen without raising a diagnostic due to -Waddr-space-convert.

gcc/
	* config/avr/builtins.def (STRLEN_FLASH, STRLEN_FLASHX)
	(STRLEN_MEMX): New DEF_BUILTIN's.
	* config/avr/avr.cc (avr_ftype_strlen): New static function.
	(avr_builtin_supported_p): New built-ins are not for AVR_TINY.
	(avr_init_builtins) <strlen_flash_node, strlen_flashx_node,
	strlen_memx_node>: Provide new fntypes.
	(avr_fold_builtin) [AVR_BUILTIN_STRLEN_FLASH]
	[AVR_BUILTIN_STRLEN_FLASHX, AVR_BUILTIN_STRLEN_MEMX]: Fold if
	possible.
	* doc/extend.texi (AVR Built-in Functions): Document
	__builtin_avr_strlen_flash, __builtin_avr_strlen_flashx,
	__builtin_avr_strlen_memx.
libgcc/
	* config/avr/t-avr (LIB1ASMFUNCS): Add _strlen_memx.
	* config/avr/lib1funcs.S <L_strlen_memx, __strlen_memx>: Implement.

2 files changed, 40 insertions, 1 deletions

diff --git a/gcc/config/avr/avr.cc b/gcc/config/avr/avr.cc
index 2b550e7..9454cb9 100644
--- a/gcc/config/avr/avr.cc
+++ b/gcc/config/avr/avr.cc
@@ -15696,7 +15696,10 @@ avr_bdesc[AVR_BUILTIN_COUNT] =
 bool
 avr_builtin_supported_p (unsigned id)
 {
-  const bool uses_as = id == AVR_BUILTIN_FLASH_SEGMENT;
+  const bool uses_as = (id == AVR_BUILTIN_FLASH_SEGMENT
+			|| id == AVR_BUILTIN_STRLEN_FLASH
+			|| id == AVR_BUILTIN_STRLEN_FLASHX
+			|| id == AVR_BUILTIN_STRLEN_MEMX);
 
   // We don't support address-spaces on Reduced Tiny.
   if (AVR_TINY && uses_as)
@@ -15732,6 +15735,25 @@ avr_init_builtin_int24 (void)
 }
 
 
+/* Return a function signature type similar to strlen, but where
+   the address is qualified by named address-space AS.  */
+
+static tree
+avr_ftype_strlen (addr_space_t as)
+{
+  tree const_AS_char_node
+    = build_qualified_type (char_type_node,
+			    TYPE_QUAL_CONST | ENCODE_QUAL_ADDR_SPACE (as));
+  tree const_AS_ptr_type_node
+    = build_pointer_type_for_mode (const_AS_char_node,
+				   avr_addr_space_pointer_mode (as), false);
+  tree size_ftype_const_AS_char_ptr
+    = build_function_type_list (size_type_node, const_AS_ptr_type_node, NULL);
+
+  return size_ftype_const_AS_char_ptr;
+}
+
+
 /* Implement `TARGET_INIT_BUILTINS' */
 /* Set up all builtin functions for this target.  */
 
@@ -15789,6 +15811,10 @@ avr_init_builtins (void)
 				const_memx_ptr_type_node,
 				NULL);
 
+  tree strlen_flash_node = avr_ftype_strlen (ADDR_SPACE_FLASH);
+  tree strlen_flashx_node = avr_ftype_strlen (ADDR_SPACE_FLASHX);
+  tree strlen_memx_node = avr_ftype_strlen (ADDR_SPACE_MEMX);
+
 #define ITYP(T)                                                         \
   lang_hooks.types.type_for_size (TYPE_PRECISION (T), TYPE_UNSIGNED (T))
 
@@ -16180,6 +16206,13 @@ avr_fold_builtin (tree fndecl, int /*n_args*/, tree *arg, bool /*ignore*/)
 			    build_int_cst (val_type, 4));
       }
 
+    case AVR_BUILTIN_STRLEN_FLASH:
+    case AVR_BUILTIN_STRLEN_FLASHX:
+    case AVR_BUILTIN_STRLEN_MEMX:
+      if (tree len = c_strlen (arg[0], 0))
+	return len;
+      break;
+
     case AVR_BUILTIN_ABSHR:
     case AVR_BUILTIN_ABSR:
     case AVR_BUILTIN_ABSLR:
diff --git a/gcc/config/avr/builtins.def b/gcc/config/avr/builtins.def
index ad75fe9..c961089 100644
--- a/gcc/config/avr/builtins.def
+++ b/gcc/config/avr/builtins.def
@@ -65,6 +65,12 @@ DEF_BUILTIN (INSERT_BITS, 3, uintQI_ftype_uintSI_uintQI_uintQI, insert_bits, NUL
 
 DEF_BUILTIN (FLASH_SEGMENT, 1, intQI_ftype_const_memx_ptr, flash_segment, NULL, attr_const)
 
+/* strlen for ASes so that __builtin_constant_p can be used wthout raising
+   a diagnostic from -Waddr-space-convert in some AVR-LibC headers.  */
+DEF_BUILTIN (STRLEN_FLASH,  1, strlen_flash_node,  nothing, "__strlen_P", attr_const) // AVR-LibC
+DEF_BUILTIN (STRLEN_FLASHX, 1, strlen_flashx_node, nothing, "strlen_PF",  attr_const) // AVR-LibC
+DEF_BUILTIN (STRLEN_MEMX,   1, strlen_memx_node,   nothing, "__strlen_memx", NULL_TREE)
+
 /* ISO/IEC TR 18037 "Embedded C"
    The following builtins are undocumented and used by stdfix.h.  */