Fix PR3117: not all nodes being legalized. The

essential problem was that the DAG can contain
random unused nodes which were never analyzed.
When remapping a value of a node being processed,
such a node may become used and need to be analyzed;
however due to operands being transformed during
analysis the node may morph into a different one.
Users of the morphing node need to be updated, and
this wasn't happening.  While there I added a bunch
of documentation and sanity checks, so I (or some
other poor soul) won't have to scratch their head
over this stuff so long trying to remember how it
was all supposed to work next time some obscure
problem pops up!  The extra sanity checking exposed
a few places where invariants weren't being preserved,
so those are fixed too.  Since some of the sanity
checking is expensive, I added a flag to turn it
on.  It is also turned on when building with
ENABLE_EXPENSIVE_CHECKS=1.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60797 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1 insertions, 1 deletions

diff --git a/Makefile.rules b/Makefile.rules
index 82a108e243..46b1ed2635 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -274,7 +274,7 @@ endif
 # appropriate preprocessor symbols.
 ifdef ENABLE_EXPENSIVE_CHECKS
   BuildMode := $(BuildMode)+Checks
-  CPP.Defines += -D_GLIBCXX_DEBUG
+  CPP.Defines += -D_GLIBCXX_DEBUG -DXDEBUG
 endif
 
 ifeq ($(ENABLE_PIC),1)