Make addPassesToEmitAssembly() look slightly more like addPassesToJITCompile().

llvm-svn: 10818

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: 10810

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

llvm-svn: 10802

llvm-svn: 10801

llvm-svn: 10800

llvm-svn: 10799

llvm-svn: 10798

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: 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

register so that LiveVariable analysis is not confused.

llvm-svn: 10773

* Implement SCCP of load instructions, implementing Transforms/SCCP/loadtest.ll
  This allows us to fold expressions like "foo"[2], even if the pointer is only
  a conditional constant.

llvm-svn: 10767

from constant memory is, but lets not take chances.

llvm-svn: 10765

llvm-svn: 10763

case that the C/C++ front-end generates.

llvm-svn: 10761

llvm-svn: 10759

llvm-svn: 10757

llvm-svn: 10756

LiveVariables::HandlePhysRegDef private they use information that is
not in memory when LiveVariables finishes the analysis.

Also update the TwoAddressInstructionPass to not use this interface.

llvm-svn: 10755