[PATCH] D14267: Add target preference for GatherAllAliases max depth

[Matt Arsenault via llvm-commits]

arsenm created this revision.
arsenm added a reviewer: hfinkel.
arsenm added a subscriber: llvm-commits.

http://reviews.llvm.org/D14267

Files:
  include/llvm/Target/TargetLowering.h
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  lib/CodeGen/TargetLoweringBase.cpp

Index: lib/CodeGen/TargetLoweringBase.cpp
===================================================================
--- lib/CodeGen/TargetLoweringBase.cpp
+++ lib/CodeGen/TargetLoweringBase.cpp
@@ -776,6 +776,7 @@
   MinFunctionAlignment = 0;
   PrefFunctionAlignment = 0;
   PrefLoopAlignment = 0;
+  GatherAllAliasesMaxDepth = 6;
   MinStackArgumentAlignment = 1;
   InsertFencesForAtomic = false;
   MinimumJumpTableEntries = 4;
Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -14467,7 +14467,7 @@
     // FIXME: The depth check could be made to return the last non-aliasing
     // chain we found before we hit a tokenfactor rather than the original
     // chain.
-    if (Depth > 6) {
+    if (Depth > TLI.getGatherAllAliasesMaxDepth()) {
       Aliases.clear();
       Aliases.push_back(OriginalChain);
       return;
Index: include/llvm/Target/TargetLowering.h
===================================================================
--- include/llvm/Target/TargetLowering.h
+++ include/llvm/Target/TargetLowering.h
@@ -833,6 +833,10 @@
     return TargetDAGCombineArray[NT >> 3] & (1 << (NT&7));
   }
 
+  unsigned getGatherAllAliasesMaxDepth() const {
+    return GatherAllAliasesMaxDepth;
+  }
+
   /// \brief Get maximum # of store operations permitted for llvm.memset
   ///
   /// This function returns the maximum number of store operations permitted
@@ -1962,6 +1966,12 @@
   ///      is[Z|FP]ExtFree of the related types is not true.
   virtual bool isExtFreeImpl(const Instruction *I) const { return false; }
 
+  /// Depth that GatherAllAliases should should continue looking for chain
+  /// dependencies when trying to find a more preferrable chain. As na
+  /// approximation, this should be more than the number of consecutive stores
+  /// expected to be merged.
+  unsigned GatherAllAliasesMaxDepth;
+
   /// \brief Specify maximum number of store instructions per memset call.
   ///
   /// When lowering \@llvm.memset this field specifies the maximum number of


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