[PATCH] D86843: [EarlyCSE] Equivalent SELECTs should hash equally

[Bryan Chan via Phabricator via llvm-commits]

bryanpkc updated this revision to Diff 288823.
bryanpkc added a comment.

Moved the fix into `matchSelectWithOptionalNotCond` instead of duplicating code.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D86843/new/

https://reviews.llvm.org/D86843

Files:
  llvm/lib/Transforms/Scalar/EarlyCSE.cpp


Index: llvm/lib/Transforms/Scalar/EarlyCSE.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/EarlyCSE.cpp
+++ llvm/lib/Transforms/Scalar/EarlyCSE.cpp
@@ -191,6 +191,18 @@
     Pred = ICmpInst::getSwappedPredicate(Pred);
   }
 
+  // Check for inverted variants of min/max by swapping operands.
+  switch (Pred) {
+  case CmpInst::ICMP_ULE:
+  case CmpInst::ICMP_UGE:
+  case CmpInst::ICMP_SLE:
+  case CmpInst::ICMP_SGE:
+    Pred = CmpInst::getInversePredicate(Pred);
+    std::swap(A, B);
+  default:
+    break;
+  }
+
   switch (Pred) {
   case CmpInst::ICMP_UGT: Flavor = SPF_UMAX; break;
   case CmpInst::ICMP_ULT: Flavor = SPF_UMIN; break;
@@ -257,6 +269,25 @@
     Value *X, *Y;
     if (!match(Cond, m_Cmp(Pred, m_Value(X), m_Value(Y))))
       return hash_combine(Inst->getOpcode(), Cond, A, B);
+#if 0
+    // Prefer to hash the select as a min/max if possible.
+    CmpInst::Predicate InvPred = CmpInst::getInversePredicate(Pred);
+    if (X == B && Y == A) {
+      switch (InvPred) {
+      case CmpInst::ICMP_UGT: SPF = SPF_UMAX; break;
+      case CmpInst::ICMP_ULT: SPF = SPF_UMIN; break;
+      case CmpInst::ICMP_SGT: SPF = SPF_SMAX; break;
+      case CmpInst::ICMP_SLT: SPF = SPF_SMIN; break;
+      default: break;
+      }
+      if (SPF == SPF_SMIN || SPF == SPF_SMAX ||
+          SPF == SPF_UMIN || SPF == SPF_UMAX) {
+        if (A > B)
+          std::swap(A, B);
+        return hash_combine(Inst->getOpcode(), SPF, A, B);
+      }
+    }
+#endif
 
     // Similar to cmp normalization (above) - canonicalize the predicate value:
     // select (icmp Pred, X, Y), A, B --> select (icmp InvPred, X, Y), B, A


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