From 11495e5acb53c05965781c1910510e588aaee27e Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev@redking.me.uk>
Date: Sun, 13 Oct 2019 19:35:35 +0000
Subject: [PATCH] [X86] getTargetShuffleInputs - Control KnownUndef mask
 element resolution as well as KnownZero.

We were already controlling whether the KnownZero elements were being written to the target mask, this extends it to the KnownUndef elements as well so we can prevent the target shuffle mask being manipulated at all.

llvm-svn: 374732
---
 llvm/lib/Target/X86/X86ISelLowering.cpp | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 52d6f67..a340eff9 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -6812,7 +6812,7 @@ static bool getTargetShuffleAndZeroables(SDValue N, SmallVectorImpl<int> &Mask,
 static bool getTargetShuffleInputs(SDValue Op, SmallVectorImpl<SDValue> &Inputs,
                                    SmallVectorImpl<int> &Mask,
                                    SelectionDAG &DAG, unsigned Depth,
-                                   bool ResolveZero);
+                                   bool ResolveKnownElts);
 
 // Attempt to decode ops that could be represented as a shuffle mask.
 // The decoded shuffle mask may contain a different number of elements to the
@@ -6821,7 +6821,7 @@ static bool getFauxShuffleMask(SDValue N, const APInt &DemandedElts,
                                SmallVectorImpl<int> &Mask,
                                SmallVectorImpl<SDValue> &Ops,
                                SelectionDAG &DAG, unsigned Depth,
-                               bool ResolveZero) {
+                               bool ResolveKnownElts) {
   Mask.clear();
   Ops.clear();
 
@@ -6916,9 +6916,9 @@ static bool getFauxShuffleMask(SDValue N, const APInt &DemandedElts,
     SmallVector<int, 64> SrcMask0, SrcMask1;
     SmallVector<SDValue, 2> SrcInputs0, SrcInputs1;
     if (!getTargetShuffleInputs(N0, SrcInputs0, SrcMask0, DAG, Depth + 1,
-                                ResolveZero) ||
+                                ResolveKnownElts) ||
         !getTargetShuffleInputs(N1, SrcInputs1, SrcMask1, DAG, Depth + 1,
-                                ResolveZero))
+                                ResolveKnownElts))
       return false;
     size_t MaskSize = std::max(SrcMask0.size(), SrcMask1.size());
     SmallVector<int, 64> Mask0, Mask1;
@@ -6966,7 +6966,7 @@ static bool getFauxShuffleMask(SDValue N, const APInt &DemandedElts,
     SmallVector<int, 64> SubMask;
     SmallVector<SDValue, 2> SubInputs;
     if (!getTargetShuffleInputs(peekThroughOneUseBitcasts(Sub), SubInputs,
-                                SubMask, DAG, Depth + 1, ResolveZero))
+                                SubMask, DAG, Depth + 1, ResolveKnownElts))
       return false;
     if (SubMask.size() != NumSubElts) {
       assert(((SubMask.size() % NumSubElts) == 0 ||
@@ -7250,7 +7250,7 @@ static bool getTargetShuffleInputs(SDValue Op, const APInt &DemandedElts,
                                    SmallVectorImpl<int> &Mask,
                                    APInt &KnownUndef, APInt &KnownZero,
                                    SelectionDAG &DAG, unsigned Depth,
-                                   bool ResolveZero) {
+                                   bool ResolveKnownElts) {
   EVT VT = Op.getValueType();
   if (!VT.isSimple() || !VT.isVector())
     return false;
@@ -7258,17 +7258,17 @@ static bool getTargetShuffleInputs(SDValue Op, const APInt &DemandedElts,
   if (getTargetShuffleAndZeroables(Op, Mask, Inputs, KnownUndef, KnownZero)) {
     for (int i = 0, e = Mask.size(); i != e; ++i) {
       int &M = Mask[i];
-      if (M < 0)
+      if (M < 0 || !ResolveKnownElts)
         continue;
       if (KnownUndef[i])
         M = SM_SentinelUndef;
-      else if (ResolveZero && KnownZero[i])
+      else if (KnownZero[i])
         M = SM_SentinelZero;
     }
     return true;
   }
   if (getFauxShuffleMask(Op, DemandedElts, Mask, Inputs, DAG, Depth,
-                         ResolveZero)) {
+                         ResolveKnownElts)) {
     KnownUndef = KnownZero = APInt::getNullValue(Mask.size());
     for (int i = 0, e = Mask.size(); i != e; ++i) {
       int M = Mask[i];
@@ -7285,7 +7285,7 @@ static bool getTargetShuffleInputs(SDValue Op, const APInt &DemandedElts,
 static bool getTargetShuffleInputs(SDValue Op, SmallVectorImpl<SDValue> &Inputs,
                                    SmallVectorImpl<int> &Mask,
                                    SelectionDAG &DAG, unsigned Depth = 0,
-                                   bool ResolveZero = true) {
+                                   bool ResolveKnownElts = true) {
   EVT VT = Op.getValueType();
   if (!VT.isSimple() || !VT.isVector())
     return false;
@@ -7294,7 +7294,7 @@ static bool getTargetShuffleInputs(SDValue Op, SmallVectorImpl<SDValue> &Inputs,
   unsigned NumElts = Op.getValueType().getVectorNumElements();
   APInt DemandedElts = APInt::getAllOnesValue(NumElts);
   return getTargetShuffleInputs(Op, DemandedElts, Inputs, Mask, KnownUndef,
-                                KnownZero, DAG, Depth, ResolveZero);
+                                KnownZero, DAG, Depth, ResolveKnownElts);
 }
 
 /// Returns the scalar element that will make up the ith
-- 
2.7.4