Fix *_EXTEND_VECTOR_INREG legalization

Summary:
While promoting *_EXTEND_VECTOR_INREG nodes whose inputs are already
promoted, perform the appropriate sign extension for the promoted node
before doing the *_EXTEND_VECTOR_INREG operation.  If not, the undefined
high-order bits of the promoted operand may (a) be garbage inc ase of
zext) or (b) contribute the wrong sign-bit (in case of sext)

Updated the promote-vec3.ll test after this change.  The diff shows
explicit zeroing in case of zext and intermediate sign extension in case
of sext.

Reviewers: RKSimon

Subscribers: llvm-commits, srhines

Differential Revision: https://reviews.llvm.org/D25790

llvm-svn: 284752

1 files changed, 19 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
index 41ca0b462f6..0669536ec13 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
@@ -3349,11 +3349,27 @@ SDValue DAGTypeLegalizer::PromoteIntRes_EXTEND_VECTOR_INREG(SDNode *N) {
 
   SDLoc dl(N);
 
-  // For operands whose TypeAction is to promote, the promoted node to construct
-  // a new *_EXTEND_VECTOR_INREG node.
+  // For operands whose TypeAction is to promote, extend the promoted node
+  // appropriately (ZERO_EXTEND or SIGN_EXTEND) from the original pre-promotion
+  // type, and then construct a new *_EXTEND_VECTOR_INREG node to the promote-to
+  // type..
   if (getTypeAction(N->getOperand(0).getValueType())
       == TargetLowering::TypePromoteInteger) {
-    SDValue Promoted = GetPromotedInteger(N->getOperand(0));
+    SDValue Promoted;
+
+    switch(N->getOpcode()) {
+      case ISD::SIGN_EXTEND_VECTOR_INREG:
+        Promoted = SExtPromotedInteger(N->getOperand(0));
+        break;
+      case ISD::ZERO_EXTEND_VECTOR_INREG:
+        Promoted = ZExtPromotedInteger(N->getOperand(0));
+        break;
+      case ISD::ANY_EXTEND_VECTOR_INREG:
+        Promoted = GetPromotedInteger(N->getOperand(0));
+        break;
+      default:
+        llvm_unreachable("Node has unexpected Opcode");
+    }
     return DAG.getNode(N->getOpcode(), dl, NVT, Promoted);
   }