[tree-ssa] Simplifying TARGET_EXPR

[Gabriel Dos Reis]

Mark Mitchell <mark@codesourcery.com> writes:

| > Do you think we should always elide copy-constructors by default,
| > unless explicitly told the contrary?
| 
| Yes.

OK, I got it -- I think we're on the same page.

[...]

|  On the other, copy constructor elision is observable
| behavior in the program, and it's going to make it hard to do
| debug, profile, and otherwise analyze your program if the number
| of copy constructor calls changes when you optimize.


Since the standard explicitly allows a compiler to elide
copy-constructors even though they have side-effects, C++ proggrammers
have come up (at least there are guidelines to that effect) not to
write programs whose semantics criticall depends on the number of
times copy-constructor/destructor are called.

I'm sympathetic to your take that we should try hard to preserve the
number of copy-constructor calls.

-- Gaby