svn commit: r286007 - in stable/10/contrib/llvm: include/llvm/CodeGen lib/CodeGen/SelectionDAG lib/Target/X86

[Dimitry Andric]

Author: dim
Date: Wed Jul 29 12:59:16 2015
New Revision: 286007
URL: https://svnweb.freebsd.org/changeset/base/286007

Log:
  Pull in r219009 from upstream llvm trunk (by Adam Nemet):
  
    [ISel] Keep matching state consistent when folding during X86 address match
  
    In the X86 backend, matching an address is initiated by the 'addr' complex
    pattern and its friends.  During this process we may reassociate and-of-shift
    into shift-of-and (FoldMaskedShiftToScaledMask) to allow folding of the
    shift into the scale of the address.
  
    However as demonstrated by the testcase, this can trigger CSE of not only the
    shift and the AND which the code is prepared for but also the underlying load
    node.  In the testcase this node is sitting in the RecordedNode and MatchScope
    data structures of the matcher and becomes a deleted node upon CSE.  Returning
    from the complex pattern function, we try to access it again hitting an assert
    because the node is no longer a load even though this was checked before.
  
    Now obviously changing the DAG this late is bending the rules but I think it
    makes sense somewhat.  Outside of addresses we prefer and-of-shift because it
    may lead to smaller immediates (FoldMaskAndShiftToScale is an even better
    example because it create a non-canonical node).  We currently don't recognize
    addresses during DAGCombiner where arguably this canonicalization should be
    performed.  On the other hand, having this in the matcher allows us to cover
    all the cases where an address can be used in an instruction.
  
    I've also talked a little bit to Dan Gohman on llvm-dev who added the RAUW for
    the new shift node in FoldMaskedShiftToScaledMask.  This RAUW is responsible
    for initiating the recursive CSE on users
    (http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-September/076903.html) but it
    is not strictly necessary since the shift is hooked into the visited user.  Of
    course it's safer to keep the DAG consistent at all times (e.g. for accurate
    number of uses, etc.).
  
    So rather than changing the fundamentals, I've decided to continue along the
    previous patches and detect the CSE.  This patch installs a very targeted
    DAGUpdateListener for the duration of a complex-pattern match and updates the
    matching state accordingly.  (Previous patches used HandleSDNode to detect the
    CSE but that's not practical here).  The listener is only installed on X86.
  
    I tested that there is no measurable overhead due to this while running
    through the spec2k BC files with llc.  The only thing we pay for is the
    creation of the listener.  The callback never ever triggers in spec2k since
    this is a corner case.
  
    Fixes rdar://problem/18206171
  
  This fixes a possible crash in x86 code generation when compiling recent
  llvm/clang trunk sources.
  
  Direct commit to stable/10, since head already has llvm/clang 3.6.1,
  which includes this fix.
  
  Reported by:	jonathan, theraven
  Upstream PR:	https://llvm.org/bugs/show_bug.cgi?id=24249

Modified:
  stable/10/contrib/llvm/include/llvm/CodeGen/SelectionDAGISel.h
  stable/10/contrib/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
  stable/10/contrib/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp

Modified: stable/10/contrib/llvm/include/llvm/CodeGen/SelectionDAGISel.h
==============================================================================
--- stable/10/contrib/llvm/include/llvm/CodeGen/SelectionDAGISel.h	Wed Jul 29 12:42:45 2015	(r286006)
+++ stable/10/contrib/llvm/include/llvm/CodeGen/SelectionDAGISel.h	Wed Jul 29 12:59:16 2015	(r286007)
@@ -238,6 +238,12 @@ public:
                            const unsigned char *MatcherTable,
                            unsigned TableSize);
 
+  /// \brief Return true if complex patterns for this target can mutate the
+  /// DAG.
+  virtual bool ComplexPatternFuncMutatesDAG() const {
+    return false;
+  }
+
 private:
 
   // Calls to these functions are generated by tblgen.

Modified: stable/10/contrib/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
==============================================================================
--- stable/10/contrib/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp	Wed Jul 29 12:42:45 2015	(r286006)
+++ stable/10/contrib/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp	Wed Jul 29 12:59:16 2015	(r286007)
@@ -2345,6 +2345,42 @@ struct MatchScope {
   bool HasChainNodesMatched, HasGlueResultNodesMatched;
 };
 
+/// \\brief A DAG update listener to keep the matching state
+/// (i.e. RecordedNodes and MatchScope) uptodate if the target is allowed to
+/// change the DAG while matching.  X86 addressing mode matcher is an example
+/// for this.
+class MatchStateUpdater : public SelectionDAG::DAGUpdateListener
+{
+      SmallVectorImpl<std::pair<SDValue, SDNode*> > &RecordedNodes;
+      SmallVectorImpl<MatchScope> &MatchScopes;
+public:
+  MatchStateUpdater(SelectionDAG &DAG,
+                    SmallVectorImpl<std::pair<SDValue, SDNode*> > &RN,
+                    SmallVectorImpl<MatchScope> &MS) :
+    SelectionDAG::DAGUpdateListener(DAG),
+    RecordedNodes(RN), MatchScopes(MS) { }
+
+  void NodeDeleted(SDNode *N, SDNode *E) {
+    // Some early-returns here to avoid the search if we deleted the node or
+    // if the update comes from MorphNodeTo (MorphNodeTo is the last thing we
+    // do, so it's unnecessary to update matching state at that point).
+    // Neither of these can occur currently because we only install this
+    // update listener during matching a complex patterns.
+    if (!E || E->isMachineOpcode())
+      return;
+    // Performing linear search here does not matter because we almost never
+    // run this code.  You'd have to have a CSE during complex pattern
+    // matching.
+    for (auto &I : RecordedNodes)
+      if (I.first.getNode() == N)
+        I.first.setNode(E);
+
+    for (auto &I : MatchScopes)
+      for (auto &J : I.NodeStack)
+        if (J.getNode() == N)
+          J.setNode(E);
+  }
+};
 }
 
 SDNode *SelectionDAGISel::
@@ -2599,6 +2635,14 @@ SelectCodeCommon(SDNode *NodeToMatch, co
       unsigned CPNum = MatcherTable[MatcherIndex++];
       unsigned RecNo = MatcherTable[MatcherIndex++];
       assert(RecNo < RecordedNodes.size() && "Invalid CheckComplexPat");
+
+      // If target can modify DAG during matching, keep the matching state
+      // consistent.
+      std::unique_ptr<MatchStateUpdater> MSU;
+      if (ComplexPatternFuncMutatesDAG())
+        MSU.reset(new MatchStateUpdater(*CurDAG, RecordedNodes,
+                                        MatchScopes));
+
       if (!CheckComplexPattern(NodeToMatch, RecordedNodes[RecNo].second,
                                RecordedNodes[RecNo].first, CPNum,
                                RecordedNodes))

Modified: stable/10/contrib/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
==============================================================================
--- stable/10/contrib/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp	Wed Jul 29 12:42:45 2015	(r286006)
+++ stable/10/contrib/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp	Wed Jul 29 12:59:16 2015	(r286007)
@@ -290,6 +290,13 @@ namespace {
     const X86InstrInfo *getInstrInfo() const {
       return getTargetMachine().getInstrInfo();
     }
+
+    /// \brief Address-mode matching performs shift-of-and to and-of-shift
+    /// reassociation in order to expose more scaled addressing
+    /// opportunities.
+    bool ComplexPatternFuncMutatesDAG() const override {
+      return true;
+    }
   };
 }