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, 7 insertions, 16 deletions

diff --git a/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp b/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
index 9510987525..9a766e283a 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
@@ -507,15 +507,10 @@ bool DAGTypeLegalizer::SoftenFloatOperand(SDNode *N, unsigned OpNo) {
   // If the result is null, the sub-method took care of registering results etc.
   if (!Res.getNode()) return false;
 
-  // If the result is N, the sub-method updated N in place.  Check to see if any
-  // operands are new, and if so, mark them.
-  if (Res.getNode() == N) {
-    // Mark N as new and remark N and its operands.  This allows us to correctly
-    // revisit N if it needs another step of promotion and allows us to visit
-    // any new operands to N.
-    ReanalyzeNode(N);
+  // If the result is N, the sub-method updated N in place.  Tell the legalizer
+  // core about this.
+  if (Res.getNode() == N)
     return true;
-  }
 
   assert(Res.getValueType() == N->getValueType(0) && N->getNumValues() == 1 &&
          "Invalid operand expansion");
@@ -1190,15 +1185,11 @@ bool DAGTypeLegalizer::ExpandFloatOperand(SDNode *N, unsigned OpNo) {
 
   // If the result is null, the sub-method took care of registering results etc.
   if (!Res.getNode()) return false;
-  // If the result is N, the sub-method updated N in place.  Check to see if any
-  // operands are new, and if so, mark them.
-  if (Res.getNode() == N) {
-    // Mark N as new and remark N and its operands.  This allows us to correctly
-    // revisit N if it needs another step of expansion and allows us to visit
-    // any new operands to N.
-    ReanalyzeNode(N);
+
+  // If the result is N, the sub-method updated N in place.  Tell the legalizer
+  // core about this.
+  if (Res.getNode() == N)
     return true;
-  }
 
   assert(Res.getValueType() == N->getValueType(0) && N->getNumValues() == 1 &&
          "Invalid operand expansion");