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.

llvm-svn: 60797

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 34f0ccac47d..979dea0d7f0 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1246,6 +1246,22 @@ SDValue SelectionDAG::CreateStackTemporary(MVT VT, unsigned minAlign) {
   return getFrameIndex(FrameIdx, TLI.getPointerTy());
 }
 
+/// CreateStackTemporary - Create a stack temporary suitable for holding
+/// either of the specified value types.
+SDValue SelectionDAG::CreateStackTemporary(MVT VT1, MVT VT2) {
+  unsigned Bytes = std::max(VT1.getStoreSizeInBits(),
+                            VT2.getStoreSizeInBits())/8;
+  const Type *Ty1 = VT1.getTypeForMVT();
+  const Type *Ty2 = VT2.getTypeForMVT();
+  const TargetData *TD = TLI.getTargetData();
+  unsigned Align = std::max(TD->getPrefTypeAlignment(Ty1),
+                            TD->getPrefTypeAlignment(Ty2));
+
+  MachineFrameInfo *FrameInfo = getMachineFunction().getFrameInfo();
+  int FrameIdx = FrameInfo->CreateStackObject(Bytes, Align);
+  return getFrameIndex(FrameIdx, TLI.getPointerTy());
+}
+
 SDValue SelectionDAG::FoldSetCC(MVT VT, SDValue N1,
                                 SDValue N2, ISD::CondCode Cond) {
   // These setcc operations always fold.