Refactor a bunch of includes so that TargetMachine.h doesn't have to include

[oota-llvm.git] / lib / CodeGen / SelectionDAG / TargetLowering.cpp

diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 81e7785a847655fc6d6ee1e747385148f29b83a2..50d2dfb16e4ddbc55580d9df78ba839e43a1d6fe 100644 (file)
--- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Target/TargetLowering.h"
+#include "llvm/Target/TargetData.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/MRegisterInfo.h"
 #include "llvm/DerivedTypes.h"
@@ -467,8 +468,14 @@ bool TargetLowering::SimplifyDemandedBits(SDOperand Op, uint64_t DemandedMask,
       HighBits <<= MVT::getSizeInBits(VT) - ShAmt;
       uint64_t TypeMask = MVT::getIntVTBitMask(VT);
       
-      if (SimplifyDemandedBits(Op.getOperand(0),
-                               (DemandedMask << ShAmt) & TypeMask,
+      uint64_t InDemandedMask = (DemandedMask << ShAmt) & TypeMask;
+
+      // If any of the demanded bits are produced by the sign extension, we also
+      // demand the input sign bit.
+      if (HighBits & DemandedMask)
+        InDemandedMask |= MVT::getIntVTSignBit(VT);
+      
+      if (SimplifyDemandedBits(Op.getOperand(0), InDemandedMask,
                                KnownZero, KnownOne, TLO, Depth+1))
         return true;
       assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 
@@ -1176,8 +1183,29 @@ unsigned TargetLowering::ComputeNumSignBits(SDOperand Op, unsigned Depth) const{
     if (NumBits > 1) return NumBits;
   }
   
-  // FIXME: Should use computemaskedbits to look at the top bits.
-  return 1;
+  // Finally, if we can prove that the top bits of the result are 0's or 1's,
+  // use this information.
+  uint64_t KnownZero, KnownOne;
+  uint64_t Mask = MVT::getIntVTBitMask(VT);
+  ComputeMaskedBits(Op, Mask, KnownZero, KnownOne, Depth);
+  
+  uint64_t SignBit = MVT::getIntVTSignBit(VT);
+  if (KnownZero & SignBit) {        // SignBit is 0
+    Mask = KnownZero;
+  } else if (KnownOne & SignBit) {  // SignBit is 1;
+    Mask = KnownOne;
+  } else {
+    // Nothing known.
+    return 1;
+  }
+  
+  // Okay, we know that the sign bit in Mask is set.  Use CLZ to determine
+  // the number of identical bits in the top of the input value.
+  Mask ^= ~0ULL;
+  Mask <<= 64-VTBits;
+  // Return # leading zeros.  We use 'min' here in case Val was zero before
+  // shifting.  We don't want to return '64' as for an i32 "0".
+  return std::min(VTBits, CountLeadingZeros_64(Mask));
 }