https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64950
Bug ID: 64950
Summary: postpone expanding va_arg till pass_stdarg
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: vries at gcc dot gnu.org
pass_stdarg optimizes cfun->va_list_gpr/fpr_size by detecting va_args.
However, va_args are expanded at gimple level, so pass_stdarg detects them by
matching what the expansion of va_arg looks like after running through the
passes between gimplification and pass_stdarg.
This is known to be fragile (see f.i. PR 41089). It makes more sense to do the
pass_stdarg optimization while va_arg is still intact. And we want to run
optimization passes before pass_stdarg to be able to eliminate some unwanted
va_args. So, it makes sense to postpone expansion of va_arg untill pass_stdarg.
Michael Matz posted a prototype patch (
https://gcc.gnu.org/ml/gcc/2015-01/msg00304.html ). Latest version availabe at
vries/expand-va-arg-at-pass-stdarg. Testing status of latest version available
at https://gcc.gnu.org/ml/gcc/2015-02/msg00020.html .
