I'm looking for an approval of the attached patch.
I've adjusted the documentation based on Sandra's input (i.e.,
documented the negative of the option rather than the positive;
thank you for the review, btw.)
On 11/08/2016 08:13 PM, Martin Sebor wrote:
The -fprintf-return-value optimization has been disabled since
the last time it caused a bootstrap failure on powerpc64le. With
the underlying problems fixed GCC has bootstrapped fine on all of
powerpc64, powerpc64le and x86_64 and tested with no regressions.
I'd like to re-enable the option. The attached patch does that.
Thanks
Martin
gcc/c-family/ChangeLog:
* c.opt (-fprintf-return-value): Enable by default.
gcc/ChangeLog:
* doc/invoke.texi (-fprintf-return-value): Document that option
is enabled by default.
Index: gcc/c-family/c.opt
===================================================================
--- gcc/c-family/c.opt (revision 242500)
+++ gcc/c-family/c.opt (working copy)
@@ -1550,7 +1550,7 @@ C++ ObjC++ Var(flag_pretty_templates) Init(1)
-fno-pretty-templates Do not pretty-print template specializations as the template signature followed by the arguments.
fprintf-return-value
-C ObjC C++ ObjC++ LTO Optimization Var(flag_printf_return_value) Init(0)
+C ObjC C++ ObjC++ LTO Optimization Var(flag_printf_return_value) Init(1)
Treat known sprintf return values as constants.
freplace-objc-classes
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi (revision 242500)
+++ gcc/doc/invoke.texi (working copy)
@@ -384,7 +384,7 @@ Objective-C and Objective-C++ Dialects}.
-fno-toplevel-reorder -fno-trapping-math -fno-zero-initialized-in-bss @gol
-fomit-frame-pointer -foptimize-sibling-calls @gol
-fpartial-inlining -fpeel-loops -fpredictive-commoning @gol
--fprefetch-loop-arrays -fprintf-return-value @gol
+-fprefetch-loop-arrays -fno-printf-return-value @gol
-fprofile-correction @gol
-fprofile-use -fprofile-use=@var{path} -fprofile-values @gol
-fprofile-reorder-functions @gol
@@ -8286,18 +8286,19 @@ dependent on the structure of loops within the sou
Disabled at level @option{-Os}.
-@item -fprintf-return-value
-@opindex fprintf-return-value
-Substitute constants for known return value of formatted output functions
-such as @code{sprintf}, @code{snprintf}, @code{vsprintf}, and @code{vsnprintf}
-(but not @code{printf} of @code{fprintf}). This transformation allows GCC
-to optimize or even eliminate branches based on the known return value of
-these functions called with arguments that are either constant, or whose
-values are known to be in a range that makes determining the exact return
-value possible. For example, both the branch and the body of the @code{if}
-statement (but not the call to @code{snprint}) can be optimized away when
-@code{i} is a 32-bit or smaller integer because the return value is guaranteed
-to be at most 8.
+@item -fno-printf-return-value
+@opindex fno-printf-return-value
+Do not substitute constants for known return value of formatted output
+functions such as @code{sprintf}, @code{snprintf}, @code{vsprintf}, and
+@code{vsnprintf} (but not @code{printf} or @code{fprintf}). This
+transformation allows GCC to optimize or even eliminate branches based
+on the known return value of these functions called with arguments that
+are either constant, or whose values are known to be in a range that
+makes determining the exact return value possible. For example, when
+@option{-fprintf-return-value} is in effect, both the branch and the
+body of the @code{if} statement (but not the call to @code{snprintf})
+can be optimized away when @code{i} is a 32-bit or smaller integer
+because the return value is guaranteed to be at most 8.
@smallexample
char buf[9];
@@ -8308,7 +8309,7 @@ if (snprintf (buf, "%08x", i) >= sizeof buf)
The @option{-fprintf-return-value} option relies on other optimizations
and yields best results with @option{-O2}. It works in tandem with the
@option{-Wformat-length} option. The @option{-fprintf-return-value}
-option is disabled by default.
+option is enabled by default.
@item -fno-peephole
@itemx -fno-peephole2
