llvm-svn: 10815

Remove checks for many common Unix programs. Our build process currently
assumes they are there and makes no provisions for any other world-views.
(We can add some of these checks back at some later time if it should prove
useful, but right now, we do not need to check to see whether "rm" exists.)

Remove checks for many common standard C headers and functions. We assume
ISO/ANSI C++, and we always use the <cfoo> versions of ANSI C's <foo.h>
headers, so these checks will not help anything.

Edit configure's warning messages for clarity and content.

Change checks for "optional" programs to default to using "true" instead of
"false", so that a failure to find, e.g., etags, will be less likely to result
in make failing.

No longer shall we check for --enable-purify or --with-purify options.
No longer shall we propagate these to the Makefiles.

configure regenerated using autoconf-2.57.

Please feel free to send me any questions or comments you have. :-)

llvm-svn: 10814

when an implicitely defined register is later used by an alias. For example:

         call foo
         %reg1024 = mov %AL

The call implicitely defines EAX but only AL is used. Before this fix
no information was available on AL. Now EAX and all its aliases except
AL get defined and die at the call instruction whereas AL lives to be
killed by the assignment.

llvm-svn: 10813

testcase test/Regression/Assembler/ConstantExprFold.llx

Note that these kinds of things only rarely show up in source code, but are
exceedingly common in the intermediate stages of algorithms like SCCP.  By
folding things (especially relational operators) that use symbolic constants,
we are able to speculatively fold more conditional branches, which can
lead to some big simplifications.

It would be easy to add a lot more special cases here, so if you notice
SCCP missing anything "obvious", you know what to make smarter.  :)

llvm-svn: 10812

llvm-svn: 10811

llvm-svn: 10810

llvm-svn: 10809

llvm-svn: 10808

Move a bunch of (now) private stuff from ConstantFolding.h into
ConstantFolding.cpp.

This _finally_ gets us to a place where we have a sane constant folder.  The
rules are:

1. LLVM clients now use ConstantExpr::get* methods to fold constants.  If they
   cannot be folded, a constantexpr is created, so these methods always return
   valid Constant*'s.
2. The implementation of ConstantExpr::get* uses the functions exposed by
   ConstantFolding.h to try to fold constants.  If they cannot be folded,
   they should return a null pointer.
3. The implementation of ConstantFolding can do whatever it wants, and only
   has one client (Constants.cpp)

This cuts down on the wierd dependencies, and eliminates the two interfaces.
The old constanthandling interface was especially bad for clients to use
because almost none of them took the failure condition into consideration,
thus leading to obscure problems.

llvm-svn: 10807

this whole refactoring: allow constant folding methods to return something
other than predefined classes, allow them to return generic Constant*'s.

llvm-svn: 10806

llvm-svn: 10805

llvm-svn: 10804

operator constant folding stuff.

llvm-svn: 10803

llvm-svn: 10802

llvm-svn: 10801

llvm-svn: 10800

llvm-svn: 10799

llvm-svn: 10798

llvm-svn: 10797

llvm-svn: 10796

llvm-svn: 10795

llvm-svn: 10794

llvm-svn: 10793

llvm-svn: 10792

llvm-svn: 10791

llvm-svn: 10790

llvm-svn: 10789

llvm-svn: 10788

llvm-svn: 10787

llvm-svn: 10786

llvm-svn: 10785

llvm-svn: 10784

llvm-svn: 10783

llvm-svn: 10782

llvm-svn: 10781

llvm-svn: 10780

llvm-svn: 10779

constants as being "true" when evaluating branches.  This was introduced
because we now create constantexprs for the constants instead of failing the
fold.

llvm-svn: 10778

llvm-svn: 10777

binary and YACC as bison -y.

llvm-svn: 10776