Change SelectionDAG type legalization to allow BUILD_VECTOR operands to be

promoted to legal types without changing the type of the vector.  This is
following a suggestion from Duncan
(http://lists.cs.uiuc.edu/pipermail/llvmdev/2009-February/019923.html).
The transformation that used to be done during type legalization is now
postponed to DAG legalization.  This allows the BUILD_VECTORs to be optimized
and potentially handled specially by target-specific code.

It turns out that this is also consistent with an optimization done by the
DAG combiner: a BUILD_VECTOR and INSERT_VECTOR_ELT may be combined by
replacing one of the BUILD_VECTOR operands with the newly inserted element;
but INSERT_VECTOR_ELT allows its scalar operand to be larger than the
element type, with any extra high bits being implicitly truncated.  The
result is a BUILD_VECTOR where one of the operands has a type larger the
the vector element type.

Any code that operates on BUILD_VECTORs may now need to be aware of the
potential type discrepancy between the vector element type and the
BUILD_VECTOR operands.  This patch updates all of the places that I could
find to handle that case.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@68996 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 15 insertions, 4 deletions

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 0f15623898..022b961331 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -768,7 +768,8 @@ void SelectionDAG::VerifyNode(SDNode *N) {
     // following checks at least makes it possible to legalize most of the time.
 //    MVT EltVT = N->getValueType(0).getVectorElementType();
 //    for (SDNode::op_iterator I = N->op_begin(), E = N->op_end(); I != E; ++I)
-//      assert(I->getValueType() == EltVT &&
+//      assert((I->getValueType() == EltVT ||
+//              I->getValueType() == TLI.getTypeToTransformTo(EltVT)) &&
 //             "Wrong operand type!");
     break;
   }
@@ -2550,8 +2551,17 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, MVT VT,
 
     // EXTRACT_VECTOR_ELT of BUILD_VECTOR is often formed while lowering is
     // expanding large vector constants.
-    if (N2C && N1.getOpcode() == ISD::BUILD_VECTOR)
-      return N1.getOperand(N2C->getZExtValue());
+    if (N2C && N1.getOpcode() == ISD::BUILD_VECTOR) {
+      SDValue Elt = N1.getOperand(N2C->getZExtValue());
+      if (Elt.getValueType() != VT) {
+        // If the vector element type is not legal, the BUILD_VECTOR operands
+        // are promoted and implicitly truncated.  Make that explicit here.
+        assert(Elt.getValueType() == TLI.getTypeToTransformTo(VT) &&
+               "Bad type for BUILD_VECTOR operand");
+        Elt = getNode(ISD::TRUNCATE, DL, VT, Elt);
+      }
+      return Elt;
+    }
 
     // EXTRACT_VECTOR_ELT of INSERT_VECTOR_ELT is often formed when vector
     // operations are lowered to scalars.
@@ -5569,7 +5579,8 @@ bool BuildVectorSDNode::isConstantSplat(APInt &SplatValue,
     if (OpVal.getOpcode() == ISD::UNDEF)
       SplatUndef |= APInt::getBitsSet(sz, BitPos, BitPos +EltBitSize);
     else if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(OpVal))
-      SplatValue |= APInt(CN->getAPIntValue()).zextOrTrunc(sz) << BitPos;
+      SplatValue |= (APInt(CN->getAPIntValue()).zextOrTrunc(EltBitSize).
+                     zextOrTrunc(sz) << BitPos);
     else if (ConstantFPSDNode *CN = dyn_cast<ConstantFPSDNode>(OpVal))
       SplatValue |= CN->getValueAPF().bitcastToAPInt().zextOrTrunc(sz) <<BitPos;
      else