Richard Guenther - Re: [PATCH][C++] Fix PR29433, make C++ use a lot less time/memory (original) (raw)

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On Tue, 20 Feb 2007, Michael Matz wrote:

Hi,

On Wed, 13 Dec 2006, Mark Mitchell wrote:

Nobody is arguing that DW_AT_name should be the huge string for the long term. However, I would argue that it should stay that huge string until we add the template arguments to debug info, and until GDB understands that information.

Okay, so the attached patch does that. On the testcase from PR29433 it has these results (on x86_64, but with -m32):

trunk, -O0, total: 1403994 kB (3:00 min) patched, -O0, total: 353658 kB (1:11 min) trunk, -O0 -g, total: 2539302 kB (3:17 min) patched, -O0 -g, total: 1668378 kB (2:32 min)

So it saves between 900MB and 1.1 GB :) [It also saves memory with -g because the strings are ggc_stddup'd again] I've removed the hand-crafted mangle_class_name_for_template and classtype_mangled_name functions and instead used the diagnostics machinery for real by not simply looking at DECL_NAME of a type (in dwarf2out), but instead use the dwarf_name langhook there. In C that will be equivalent to using DECL_NAME in C++ it will call cxx_printable_name, which prints nice (long) names for complicated types. The verbosity needs to be 2 for that, and instead of adding yet another langhook or wrapper function which is called just once, I've called it directly.

I noticed dwarf_name is mapped to decl_printable_name for C++ and we can gain another xstrdup/free if we implement the dwarf_name langhook for C++ by simply using cp/error.c:lang_decl_name. This way we avoid using the cxx_printable_name ring buffer for function decls.

This might shave off a few seconds in compile time and a few bytes off peak memory usage.

Richard.

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