[llvm-commits] [llvm] r164628 - in /llvm/trunk: include/llvm/Target/TargetLowering.h lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp lib/CodeGen/SelectionDAG/TargetLowering.cpp lib/Target/Hexagon/HexagonISelLowering.cpp

[Sebastian Pop]

Author: spop
Date: Tue Sep 25 15:35:36 2012
New Revision: 164628

URL: http://llvm.org/viewvc/llvm-project?rev=164628&view=rev
Log:
TargetLowering interface to set/get minimum block entries for jump tables.

Provide interface in TargetLowering to set or get the minimum number of basic
blocks whereby jump tables are generated for switch statements rather than an
if sequence.

    getMinimumJumpTableEntries() defaults to 4.
    setMinimumJumpTableEntries() allows target configuration.

    This patch changes the default for the Hexagon architecture to 5
    as it improves performance on some benchmarks.

Modified:
    llvm/trunk/include/llvm/Target/TargetLowering.h
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
    llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp
    llvm/trunk/lib/Target/Hexagon/HexagonISelLowering.cpp

Modified: llvm/trunk/include/llvm/Target/TargetLowering.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Target/TargetLowering.h?rev=164628&r1=164627&r2=164628&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Target/TargetLowering.h (original)
+++ llvm/trunk/include/llvm/Target/TargetLowering.h Tue Sep 25 15:35:36 2012
@@ -712,6 +712,12 @@
     return SupportJumpTables;
   }
 
+  /// getMinimumJumpTableEntries - return integer threshold on number of
+  /// blocks to use jump tables rather than if sequence.
+  int getMinimumJumpTableEntries() const {
+    return MinimumJumpTableEntries;
+  }
+
   /// getStackPointerRegisterToSaveRestore - If a physical register, this
   /// specifies the register that llvm.savestack/llvm.restorestack should save
   /// and restore.
@@ -1032,6 +1038,12 @@
     SupportJumpTables = Val;
   }
 
+  /// setMinimumJumpTableEntries - Indicate the number of blocks to generate
+  /// jump tables rather than if sequence.
+  void setMinimumJumpTableEntries(int Val) {
+    MinimumJumpTableEntries = Val;
+  }
+
   /// setStackPointerRegisterToSaveRestore - If set to a physical register, this
   /// specifies the register that llvm.savestack/llvm.restorestack should save
   /// and restore.
@@ -1826,6 +1838,9 @@
   /// If it's not true, then each jumptable must be lowered into if-then-else's.
   bool SupportJumpTables;
 
+  /// MinimumJumpTableEntries - Number of blocks threshold to use jump tables.
+  int MinimumJumpTableEntries;
+
   /// BooleanContents - Information about the contents of the high-bits in
   /// boolean values held in a type wider than i1.  See getBooleanContents.
   BooleanContent BooleanContents;

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp?rev=164628&r1=164627&r2=164628&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Tue Sep 25 15:35:36 2012
@@ -2093,7 +2093,7 @@
   for (CaseItr I = CR.Range.first, E = CR.Range.second; I != E; ++I)
     TSize += I->size();
 
-  if (!areJTsAllowed(TLI) || TSize.ult(4))
+  if (!areJTsAllowed(TLI) || TSize.ult(TLI.getMinimumJumpTableEntries()))
     return false;
 
   APInt Range = ComputeRange(First, Last);
@@ -2565,9 +2565,10 @@
     if (handleSmallSwitchRange(CR, WorkList, SV, Default, SwitchMBB))
       continue;
 
-    // If the switch has more than 5 blocks, and at least 40% dense, and the
+    // If the switch has more than N blocks, and is at least 40% dense, and the
     // target supports indirect branches, then emit a jump table rather than
     // lowering the switch to a binary tree of conditional branches.
+    // N defaults to 4 and is controlled via TLS.getMinimumJumpTableEntries().
     if (handleJTSwitchCase(CR, WorkList, SV, Default, SwitchMBB))
       continue;
 

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp?rev=164628&r1=164627&r2=164628&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp Tue Sep 25 15:35:36 2012
@@ -613,6 +613,7 @@
   ShouldFoldAtomicFences = false;
   InsertFencesForAtomic = false;
   SupportJumpTables = true;
+  MinimumJumpTableEntries = 4;
 
   InitLibcallNames(LibcallRoutineNames);
   InitCmpLibcallCCs(CmpLibcallCCs);

Modified: llvm/trunk/lib/Target/Hexagon/HexagonISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Hexagon/HexagonISelLowering.cpp?rev=164628&r1=164627&r2=164628&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Hexagon/HexagonISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/Hexagon/HexagonISelLowering.cpp Tue Sep 25 15:35:36 2012
@@ -1350,6 +1350,8 @@
     } else {
       setOperationAction(ISD::BR_JT, MVT::Other, Expand);
     }
+    // Increase jump tables cutover to 5, was 4.
+    setMinimumJumpTableEntries(5);
 
     setOperationAction(ISD::BR_CC, MVT::i32, Expand);