[llvm-branch-commits] [llvm] [DA] Hoist division check for early exit in weakCrossingSIVtest (NFC) (PR #188442)

[Ryotaro Kasuga via llvm-branch-commits]

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@@ -1428,6 +1428,27 @@ bool DependenceInfo::weakCrossingSIVtest(const SCEV *Coeff,
     return true;
   }
 
+  // check that Coeff divides Delta
+  APInt APDelta = ConstDelta->getAPInt();
+  APInt APCoeff = ConstCoeff->getAPInt();
+  APInt Distance = APDelta; // these need to be initialzed
+  APInt Remainder = APDelta;
+  APInt::sdivrem(APDelta, APCoeff, Distance, Remainder);
+  LLVM_DEBUG(dbgs() << "\t    Remainder = " << Remainder << "\n");
+  if (Remainder != 0) {
+    // Coeff doesn't divide Delta, no dependence
+    ++WeakCrossingSIVindependence;
+    ++WeakCrossingSIVsuccesses;
+    return true;
+  }
+  LLVM_DEBUG(dbgs() << "\t    Distance = " << Distance << "\n");
+  // if 2*Coeff doesn't divide Delta, then the equal direction isn't possible
+  if (Distance[0]) {
+    // Equal direction isn't possible
+    Result.DV[Level].Direction &= ~Dependence::DVEntry::EQ;
+    ++WeakCrossingSIVsuccesses;
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kasuga-fj wrote:

I don't know how useful this metrics is, but with this change, the value could be incremented twice within a single invocation (when `Delta % (2*Coeff) != 0` and `Delta >s ML`).

https://github.com/llvm/llvm-project/pull/188442