[PATCH] D32253: [APInt] Implement APInt::intersects without creating a temporary APInt in the multiword case

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.

This is a simple question we should be able to answer without creating a temporary to hold the AND result. We can also get an early out as soon as we find a word that intersects.


https://reviews.llvm.org/D32253

Files:
  include/llvm/ADT/APInt.h
  lib/Support/APInt.cpp


Index: lib/Support/APInt.cpp
===================================================================
--- lib/Support/APInt.cpp
+++ lib/Support/APInt.cpp
@@ -722,6 +722,14 @@
   return Count;
 }
 
+bool APInt::intersectsSlowCase(const APInt &RHS) const {
+  for (unsigned i = 0, e = getNumWords(); i != e; ++i)
+    if ((pVal[i] & RHS.pVal[i]) != 0)
+      return true;
+
+  return false;
+}
+
 APInt APInt::byteSwap() const {
   assert(BitWidth >= 16 && BitWidth % 16 == 0 && "Cannot byteswap!");
   if (BitWidth == 16)
Index: include/llvm/ADT/APInt.h
===================================================================
--- include/llvm/ADT/APInt.h
+++ include/llvm/ADT/APInt.h
@@ -209,6 +209,9 @@
   /// out-of-line slow case for countPopulation
   unsigned countPopulationSlowCase() const LLVM_READONLY;
 
+  /// out-of-line slow case for intersects.
+  bool intersectsSlowCase(const APInt &RHS) const LLVM_READONLY;
+
   /// out-of-line slow case for setBits.
   void setBitsSlowCase(unsigned loBit, unsigned hiBit);
 
@@ -1204,9 +1207,10 @@
   /// This operation tests if there are any pairs of corresponding bits
   /// between this APInt and RHS that are both set.
   bool intersects(const APInt &RHS) const {
-    APInt temp(*this);
-    temp &= RHS;
-    return temp != 0;
+    assert(BitWidth == RHS.BitWidth && "Bit widths must be the same");
+    if (isSingleWord())
+      return (VAL & RHS.VAL) != 0;
+    return intersectsSlowCase(RHS);
   }
 
   /// @}


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