[llvm] r301403 - [DAG] add FIXME comments for splat detection; NFC

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Wed Apr 26 08:27:57 2017
New Revision: 301403

URL: http://llvm.org/viewvc/llvm-project?rev=301403&view=rev
Log:
[DAG] add FIXME comments for splat detection; NFC

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=301403&r1=301402&r2=301403&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Wed Apr 26 08:27:57 2017
@@ -7640,6 +7640,8 @@ bool BuildVectorSDNode::isConstantSplat(
   if (MinSplatBits > VecWidth)
     return false;
 
+  // FIXME: The widths are based on this node's type, but build vectors can
+  // truncate their operands. 
   SplatValue = APInt(VecWidth, 0);
   SplatUndef = APInt(VecWidth, 0);
 
@@ -7669,6 +7671,8 @@ bool BuildVectorSDNode::isConstantSplat(
   // The build_vector is all constants or undefs. Find the smallest element
   // size that splats the vector.
   HasAnyUndefs = (SplatUndef != 0);
+
+  // FIXME: This does not work for vectors with elements less than 8 bits.
   while (VecWidth > 8) {
     unsigned HalfSize = VecWidth / 2;
     APInt HighValue = SplatValue.lshr(HalfSize).trunc(HalfSize);

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp?rev=301403&r1=301402&r2=301403&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp Wed Apr 26 08:27:57 2017
@@ -1364,6 +1364,9 @@ unsigned TargetLowering::ComputeNumSignB
   return 1;
 }
 
+// FIXME: Ideally, this would use ISD::isConstantSplatVector(), but that must
+// work with truncating build vectors and vectors with elements of less than
+// 8 bits.
 bool TargetLowering::isConstTrueVal(const SDNode *N) const {
   if (!N)
     return false;