From 6ff5de4b1d88af62d9b1e92c9a7b5166f9b23260 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Wed, 26 Aug 2009 16:06:11 +0000
Subject: [PATCH] Add comments detailing a known bug, so that people writing
 other backends don't use it as an example.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80105 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/PIC16/PIC16ISelLowering.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lib/Target/PIC16/PIC16ISelLowering.cpp b/lib/Target/PIC16/PIC16ISelLowering.cpp
index d4cbc0a1c3b..7a5b5ff40df 100644
--- a/lib/Target/PIC16/PIC16ISelLowering.cpp
+++ b/lib/Target/PIC16/PIC16ISelLowering.cpp
@@ -533,6 +533,10 @@ SDValue PIC16TargetLowering::ExpandStore(SDNode *N, SelectionDAG &DAG) {
     SDValue SrcLo, SrcHi;
     GetExpandedParts(Src, DAG, SrcLo, SrcHi);
     SDValue ChainLo = Chain, ChainHi = Chain;
+    // FIXME: This makes unsafe assumptions. The Chain may be a TokenFactor
+    // created for an unrelated purpose, in which case it may not have
+    // exactly two operands. Also, even if it does have two operands, they
+    // may not be the low and high parts of an aligned load that was split.
     if (Chain.getOpcode() == ISD::TokenFactor) {
       ChainLo = Chain.getOperand(0);
       ChainHi = Chain.getOperand(1);
@@ -560,16 +564,19 @@ SDValue PIC16TargetLowering::ExpandStore(SDNode *N, SelectionDAG &DAG) {
     GetExpandedParts(SrcHi, DAG, SrcHi1, SrcHi2);
 
     SDValue ChainLo = Chain, ChainHi = Chain;
+    // FIXME: This makes unsafe assumptions; see the FIXME above.
     if (Chain.getOpcode() == ISD::TokenFactor) {  
       ChainLo = Chain.getOperand(0);
       ChainHi = Chain.getOperand(1);
     }
     SDValue ChainLo1 = ChainLo, ChainLo2 = ChainLo, ChainHi1 = ChainHi,
             ChainHi2 = ChainHi;
+    // FIXME: This makes unsafe assumptions; see the FIXME above.
     if (ChainLo.getOpcode() == ISD::TokenFactor) {
       ChainLo1 = ChainLo.getOperand(0);
       ChainLo2 = ChainLo.getOperand(1);
     }
+    // FIXME: This makes unsafe assumptions; see the FIXME above.
     if (ChainHi.getOpcode() == ISD::TokenFactor) {
       ChainHi1 = ChainHi.getOperand(0);
       ChainHi2 = ChainHi.getOperand(1);
@@ -601,6 +608,7 @@ SDValue PIC16TargetLowering::ExpandStore(SDNode *N, SelectionDAG &DAG) {
     SDValue SrcLo, SrcHi;
     GetExpandedParts(Src, DAG, SrcLo, SrcHi);
     SDValue ChainLo = Chain, ChainHi = Chain;
+    // FIXME: This makes unsafe assumptions; see the FIXME above.
     if (Chain.getOpcode() == ISD::TokenFactor) {
       ChainLo = Chain.getOperand(0);
       ChainHi = Chain.getOperand(1);