[llvm] [DependenceAnalysis] Improve debug messages (PR #156367)

[Ryotaro Kasuga via llvm-commits]

================
@@ -3500,17 +3512,27 @@ bool DependenceInfo::tryDelinearizeParametricSize(
   // to the dependency checks.
   if (!DisableDelinearizationChecks)
     for (size_t I = 1; I < Size; ++I) {
-      if (!isKnownNonNegative(SrcSubscripts[I], SrcPtr))
-        return false;
-
-      if (!isKnownLessThan(SrcSubscripts[I], Sizes[I - 1]))
-        return false;
-
-      if (!isKnownNonNegative(DstSubscripts[I], DstPtr))
-        return false;
+      bool SNN = isKnownNonNegative(SrcSubscripts[I], SrcPtr);
+      bool DNN = isKnownNonNegative(DstSubscripts[I], DstPtr);
+      bool SLT = isKnownLessThan(SrcSubscripts[I], Sizes[I - 1]);
+      bool DLT = isKnownLessThan(DstSubscripts[I], Sizes[I - 1]);
+      if (SNN && DNN && SLT && DLT)
+        continue;
 
-      if (!isKnownLessThan(DstSubscripts[I], Sizes[I - 1]))
-        return false;
+      LLVM_DEBUG({
+        dbgs() << "Delinearization checks failed: can't prove the following\n";
+        if (!SNN)
+          dbgs() << "  isKnownNonNegative(" << *SrcSubscripts[I] << ")\n";
+        if (!DNN)
+          dbgs() << "  isKnownNonNegative(" << *DstSubscripts[I] << ")\n";
+        if (!SLT)
+          dbgs() << "  isKnownLessThan(" << *SrcSubscripts[I] << ", "
+                 << *Sizes[I - 1] << ")\n";
+        if (!DLT)
+          dbgs() << "  isKnownLessThan(" << *DstSubscripts[I] << ", "
+                 << *Sizes[I - 1] << ")\n";
+      });
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kasuga-fj wrote:

I'm not talking about parsing debug outputs. The point here is to prevent an increase in messy or unorganized logging. 

After posting my earlier comment, I realized that these messages should probably be placed inside `isKnownNonNegative` and `isKnownLessThan`, respectively.

https://github.com/llvm/llvm-project/pull/156367