From 926dc168c893e1848a18e45fd78f9b99d6f4cd5d Mon Sep 17 00:00:00 2001
From: Jim Grosbach <grosbach@apple.com>
Date: Thu, 28 Jun 2012 21:03:44 +0000
Subject: [PATCH] 'Promote' vector [su]int_to_fp should widen elements.

Teach vector legalization how to honor Promote for int to float
conversions. The code checking whether to promote the operation knew
to look at the operand, but the actual promotion code didn't. This
fixes that. The operand is promoted up via [zs]ext.

rdar://11762659

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159378 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../SelectionDAG/LegalizeVectorOps.cpp        | 57 ++++++++++++++++++-
 1 file changed, 54 insertions(+), 3 deletions(-)

diff --git a/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp b/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
index 9fe4480d113..704f99bcf0e 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
@@ -71,6 +71,9 @@ class VectorLegalizer {
   // operands to a different type and bitcasting the result back to the
   // original type.
   SDValue PromoteVectorOp(SDValue Op);
+  // Implements [SU]INT_TO_FP vector promotion; this is a [zs]ext of the input
+  // operand to the next size up.
+  SDValue PromoteVectorOpINT_TO_FP(SDValue Op);
 
   public:
   bool Run();
@@ -231,9 +234,19 @@ SDValue VectorLegalizer::LegalizeOp(SDValue Op) {
 
   switch (TLI.getOperationAction(Node->getOpcode(), QueryType)) {
   case TargetLowering::Promote:
-    // "Promote" the operation by bitcasting
-    Result = PromoteVectorOp(Op);
-    Changed = true;
+    switch (Op.getOpcode()) {
+    default:
+      // "Promote" the operation by bitcasting
+      Result = PromoteVectorOp(Op);
+      Changed = true;
+      break;
+    case ISD::SINT_TO_FP:
+    case ISD::UINT_TO_FP:
+      // "Promote" the operation by extending the operand.
+      Result = PromoteVectorOpINT_TO_FP(Op);
+      Changed = true;
+      break;
+    }
     break;
   case TargetLowering::Legal: break;
   case TargetLowering::Custom: {
@@ -293,6 +306,44 @@ SDValue VectorLegalizer::PromoteVectorOp(SDValue Op) {
   return DAG.getNode(ISD::BITCAST, dl, VT, Op);
 }
 
+SDValue VectorLegalizer::PromoteVectorOpINT_TO_FP(SDValue Op) {
+  // INT_TO_FP operations may require the input operand be promoted even
+  // when the type is otherwise legal.
+  EVT VT = Op.getOperand(0).getValueType();
+  assert(Op.getNode()->getNumValues() == 1 &&
+         "Can't promote a vector with multiple results!");
+
+  // Normal getTypeToPromoteTo() doesn't work here, as that will promote
+  // by widening the vector w/ the same element width and twice the number
+  // of elements. We want the other way around, the same number of elements,
+  // each twice the width.
+  //
+  // Increase the bitwidth of the element to the next pow-of-two
+  // (which is greater than 8 bits).
+  unsigned NumElts = VT.getVectorNumElements();
+  EVT EltVT = VT.getVectorElementType();
+  EltVT = EVT::getIntegerVT(*DAG.getContext(), 2 * EltVT.getSizeInBits());
+  assert(EltVT.isSimple() && "Promoting to a non-simple vector type!");
+
+  // Build a new vector type and check if it is legal.
+  MVT NVT = MVT::getVectorVT(EltVT.getSimpleVT(), NumElts);
+
+  DebugLoc dl = Op.getDebugLoc();
+  SmallVector<SDValue, 4> Operands(Op.getNumOperands());
+
+  unsigned Opc = Op.getOpcode() == ISD::UINT_TO_FP ? ISD::ZERO_EXTEND :
+    ISD::SIGN_EXTEND;
+  for (unsigned j = 0; j != Op.getNumOperands(); ++j) {
+    if (Op.getOperand(j).getValueType().isVector())
+      Operands[j] = DAG.getNode(Opc, dl, NVT, Op.getOperand(j));
+    else
+      Operands[j] = Op.getOperand(j);
+  }
+
+  return DAG.getNode(Op.getOpcode(), dl, Op.getValueType(), &Operands[0],
+                     Operands.size());
+}
+
 
 SDValue VectorLegalizer::ExpandLoad(SDValue Op) {
   DebugLoc dl = Op.getDebugLoc();