GCC's default optimization level is -O0. Unfortunately unlike other compilers,
GCC generates extremely inefficient code with -O0. It is almost unusable for
low-level debugging or manual inspection of generated code. So a -O option is
always required for compilation. -Og not only allows for fast compilation, but
also produces code that is efficient, readable as well as debuggable.
Therefore -Og makes for a much better default setting.
Any comments?
2017-10-26 Wilco Dijkstra <wdijk...@arm.com>
* opts.c (default_options_optimization): Set default to -Og.
doc/
* invoke.texi (-O0) Remove default mention.
(-Og): Add mention of default setting.
--
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index
3328a3b5fafa6a98007eff52d2a26af520de9128..74c33ea35b9f320b419a3417e6007d2391536f1b
100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -7343,7 +7343,7 @@ by @option{-O2} and also turns on the following
optimization flags:
@item -O0
@opindex O0
Reduce compilation time and make debugging produce the expected
-results. This is the default.
+results.
@item -Os
@opindex Os
@@ -7371,7 +7371,7 @@ Optimize debugging experience. @option{-Og} enables
optimizations
that do not interfere with debugging. It should be the optimization
level of choice for the standard edit-compile-debug cycle, offering
a reasonable level of optimization while maintaining fast compilation
-and a good debugging experience.
+and a good debugging experience. This is the default.
@end table
If you use multiple @option{-O} options, with or without level numbers,
diff --git a/gcc/opts.c b/gcc/opts.c
index
dfad955e220870a3250198640f3790c804b191e0..74511215309f11445685db4894be2ab6881695d3
100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -565,6 +565,12 @@ default_options_optimization (struct gcc_options *opts,
int opt2;
bool openacc_mode = false;
+ /* Set the default optimization to -Og. */
+ opts->x_optimize_size = 0;
+ opts->x_optimize = 1;
+ opts->x_optimize_fast = 0;
+ opts->x_optimize_debug = 1;
+
/* Scan to see what optimization level has been specified. That will
determine the default value of many flags. */
for (i = 1; i < decoded_options_count; i++)
