This allows pointers to aggregate objects, whose elements are only read, to
be promoted and passed in by element instead of by reference.  This can
enable a LOT of subsequent optimizations in the caller function.

It's worth pointing out that this stuff happens a LOT of C++ programs, because
objects in templates are generally passed around by reference.  When these
templates are instantiated on small aggregate or scalar types, however, it is
more efficient to pass them in by value than by reference.

This transformation triggers most on C++ codes (e.g. 334 times on eon), but
does happen on C codes as well.  For example, on mesa it triggers 72 times,
and on gcc it triggers 35 times.  this is amazingly good considering that
we are using 'basicaa' so far.

llvm-svn: 12202

llvm-svn: 12201

llvm-svn: 12200

llvm-svn: 12199

llvm-svn: 12198

a zero value is the most likely way to cause further simplification, so we do it.

llvm-svn: 12197

llvm-svn: 12196

llvm-svn: 12195

llvm-svn: 12194

variables.

llvm-svn: 12193

llvm-svn: 12192

llvm-svn: 12190

llvm-svn: 12189

llvm-svn: 12188

llvm-svn: 12187

Emit RETL instruction to return instead of funny JMPL.
Fix indentation.

llvm-svn: 12186

Add RET, RETL.  Rename SAVE, RESTORE & JMPL for consistency.

llvm-svn: 12185

llvm-svn: 12184

llvm-svn: 12183

llvm-svn: 12182

llvm-svn: 12180

llvm-svn: 12169

llvm-svn: 12161

llvm-svn: 12143

llvm-svn: 12128

llvm-svn: 12127

llvm-svn: 12126

This reduces CBU time from 145s -> 122s (debug build), reduces # allocated nodes
from 129420 to 116477.

llvm-svn: 12125

llvm-svn: 12124

llvm-svn: 12123

llvm-svn: 12122

llvm-svn: 12120

llvm-svn: 12119

llvm-svn: 12118

The problem was that we were merging a field of a node with a value that was
deleted.  Thanks to bugpoint for reducing povray to a nice small 3 function
example.  :)

llvm-svn: 12116

Make sure to scope the NodeMap passed into cloneInto so that it doesn't point
to nodes that are deleted.  Add some FIXME's for future performance enhancements.

llvm-svn: 12115

llvm-svn: 12113

llvm-svn: 12112

llvm-svn: 12111

llvm-svn: 12110