> In this case it's fold-all-builtins folding a strlen call with a > PHI <"foo", "bar"> argument. IMHO not presenting RTL with such > non-sense is best achieved by not letting TER do constant propagation > (because it doesn't "fold" the result). We can never rule out such > stray non-propagated constants, so that makes expand more robust > (and hopes for RTL CCP). > > Index: gcc/tree-ssa-ter.c > =================================================================== > --- gcc/tree-ssa-ter.c (revision 204664) > +++ gcc/tree-ssa-ter.c (working copy) > @@ -438,6 +439,12 @@ ter_is_replaceable_p (gimple stmt) > && !is_gimple_val (gimple_assign_rhs1 (stmt))) > return false; > > + /* Do not propagate "modeless" constants - we may end up > confusing the RTL > + expanders. Leave the optimization to RTL CCP. */ > + if (gimple_assign_single_p (stmt) > + && CONSTANT_CLASS_P (gimple_assign_rhs1 (stmt))) > + return false; > + > return true; > } > return false; > > does that make sense? I'll test it then.
I agree with Joern that we want more constant propagation/folding during RTL expansion, not less, so IMO that's the wrong direction. -- Eric Botcazou
