[llvm] [DA] Rewrite BanerjeeMIV test with safe APInt interval arithmetic (PR #207662)

[Ruoyu Qiu via llvm-commits]

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@@ -1962,464 +2093,251 @@ bool DependenceInfo::banerjeeMIVtest(const SCEV *Src, const SCEV *Dst,
 
   LLVM_DEBUG(dbgs() << "starting Banerjee\n");
   ++BanerjeeApplications;
-  LLVM_DEBUG(dbgs() << "    Src = " << *Src << '\n');
-  const SCEV *A0;
-  SmallVector<CoefficientInfo, 4> A;
-  collectCoeffInfo(Src, true, A0, A);
-  LLVM_DEBUG(dbgs() << "    Dst = " << *Dst << '\n');
-  const SCEV *B0;
-  SmallVector<CoefficientInfo, 4> B;
-  collectCoeffInfo(Dst, false, B0, B);
-  SmallVector<BoundInfo, 4> Bound(MaxLevels + 1);
-  const SCEV *Delta = minusSCEVNoSignedOverflow(B0, A0, *SE);
-  if (!Delta)
-    return false;
-  LLVM_DEBUG(dbgs() << "\tDelta = " << *Delta << '\n');
-
-  // Compute bounds for all the * directions.
-  LLVM_DEBUG(dbgs() << "\tBounds[*]\n");
-  for (unsigned K = 1; K <= MaxLevels; ++K) {
-    Bound[K].Iterations = A[K].Iterations ? A[K].Iterations : B[K].Iterations;
-    Bound[K].Direction = Dependence::DVEntry::ALL;
-    Bound[K].DirSet = Dependence::DVEntry::NONE;
-    findBoundsALL(A, B, Bound, K);
-#ifndef NDEBUG
-    LLVM_DEBUG(dbgs() << "\t    " << K << '\t');
-    if (Bound[K].Lower[Dependence::DVEntry::ALL])
-      LLVM_DEBUG(dbgs() << *Bound[K].Lower[Dependence::DVEntry::ALL] << '\t');
-    else
-      LLVM_DEBUG(dbgs() << "-inf\t");
-    if (Bound[K].Upper[Dependence::DVEntry::ALL])
-      LLVM_DEBUG(dbgs() << *Bound[K].Upper[Dependence::DVEntry::ALL] << '\n');
-    else
-      LLVM_DEBUG(dbgs() << "+inf\n");
-#endif
-  }
 
-  // Test the *, *, *, ... case.
-  bool Disproved = false;
-  if (testBounds(Dependence::DVEntry::ALL, 0, Bound, Delta)) {
-    // Explore the direction vector hierarchy.
-    unsigned DepthExpanded = 0;
-    unsigned NewDeps =
-        exploreDirections(1, A, B, Bound, Loops, DepthExpanded, Delta);
-    if (NewDeps > 0) {
-      bool Improved = false;
-      for (unsigned K = 1; K <= CommonLevels; ++K) {
-        if (Loops[K]) {
-          unsigned Old = Result.DV[K - 1].Direction;
-          Result.DV[K - 1].Direction = Old & Bound[K].DirSet;
-          Improved |= Old != Result.DV[K - 1].Direction;
-          if (!Result.DV[K - 1].Direction) {
-            Improved = false;
-            Disproved = true;
-            break;
-          }
-        }
-      }
-      if (Improved)
-        ++BanerjeeSuccesses;
-    } else {
-      ++BanerjeeIndependence;
-      Disproved = true;
+  unsigned SrcBits = SE->getTypeSizeInBits(Src->getType());
+  unsigned DstBits = SE->getTypeSizeInBits(Dst->getType());
+  unsigned BaseBits = std::max(SrcBits, DstBits);
+  // Accepted coefficients and constants fit in signed BaseBits, and loop
+  // bounds fit in unsigned BaseBits. WideBits is large enough for products of
+  // those values and for summing one interval term per loop level.
+  unsigned WideBits = std::max(8u, 2 * BaseBits + MaxLevels + 8);
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cabbaken wrote:

I did it logically as debug code, without double-checking.

https://github.com/llvm/llvm-project/pull/207662