Hello,
this patch adds variable tracking pass - it tracks where the variables
are located at each position in code and generates location lists.
GDB 6.x can read this information and show value of variables even
in optimized code, i.e. variables in registers, variables on stack
addressed using stack pointer, variables whose location changes in the
function, ...
Variable tracking takes about 2% of compile time and is enabled by
default when compiling with debug info and optimization.
I know GCC is in stage 2 but GDB people would like GCC to generate
location lists...
I think the risk of breaking something is really small. The risk is
almost zero when we disable it by default.
Bootstrapped/regtested x86-64.
OK for mainline?