[Ada] implementation_defined_pragmas.rst: Update Initialize_Scalars docs

2019-12-13  Ghjuvan Lacambre  <lacambre@adacore.com>

gcc/ada/

	* doc/gnat_rm/implementation_defined_pragmas.rst: Update
	Initialize_Scalars documentation.
	* gnat_rm.texi: Regenerate.

From-SVN: r279366

gcc/ada/ChangeLog

+2019-12-13  Ghjuvan Lacambre  <lacambre@adacore.com>
+
+	* doc/gnat_rm/implementation_defined_pragmas.rst: Update
+	Initialize_Scalars documentation.
+	* gnat_rm.texi: Regenerate.
+
 2019-12-13  Javier Miranda  <miranda@adacore.com>
 
 	* sem_ch13.adb (Analyze_Aspect_Specification): Processing a

gcc/ada/doc/gnat_rm/implementation_defined_pragmas.rst

@@ -3057,7 +3057,9 @@ different ways:
   particular family of scalar types using the optional arguments of the pragma.
 
   The compile-time approach is intended to optimize the generated code for the
-  pragma, by possibly using fast operations such as ``memset``.
+  pragma, by possibly using fast operations such as ``memset``. Note that such
+  optimizations require using values the bytes of which all have the same
+  binary representation.
 
 * At bind time, the programmer has several options:
 
@@ -3077,7 +3079,7 @@ different ways:
   The bind-time approach is intended to provide fast turnaround for testing
   with different values, without having to recompile the program.
 
-* At execution time, the programmer can speify the invalid values using an
+* At execution time, the programmer can specify the invalid values using an
   environment variable. See the GNAT User's Guide for details.
 
   The execution-time approach is intended to provide fast turnaround for

gcc/ada/gnat_rm.texi

@@ -4508,7 +4508,9 @@ At compile time, the programmer can specify the invalid value for a
 particular family of scalar types using the optional arguments of the pragma.
 
 The compile-time approach is intended to optimize the generated code for the
-pragma, by possibly using fast operations such as @code{memset}.
+pragma, by possibly using fast operations such as @code{memset}. Note that such
+optimizations require using values the bytes of which all have the same
+binary representation.
 
 @item 
 At bind time, the programmer has several options:
@@ -4538,7 +4540,7 @@ The bind-time approach is intended to provide fast turnaround for testing
 with different values, without having to recompile the program.
 
 @item 
-At execution time, the programmer can speify the invalid values using an
+At execution time, the programmer can specify the invalid values using an
 environment variable. See the GNAT User's Guide for details.
 
 The execution-time approach is intended to provide fast turnaround for