[llvm] Optimize fptrunc(x)>=C1 --> x>=C2 (PR #99475)

[Matt Arsenault via llvm-commits]

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@@ -7882,6 +7892,79 @@ static Instruction *foldFCmpReciprocalAndZero(FCmpInst &I, Instruction *LHSI,
   return new FCmpInst(Pred, LHSI->getOperand(1), RHSC, "", &I);
 }
 
+// Fold trunc(x) < constant --> x < constant if possible.
+static Instruction *foldFCmpFpTrunc(FCmpInst &I, Instruction *LHSI,
+                                    Constant *RHSC) {
+  FCmpInst::Predicate Pred = I.getPredicate();
+  bool RoundDown = false;
+
+  if ((Pred == FCmpInst::FCMP_OGE) || (Pred == FCmpInst::FCMP_UGE) ||
+      (Pred == FCmpInst::FCMP_OLT) || (Pred == FCmpInst::FCMP_ULT))
+    RoundDown = true;
+  else if ((Pred == FCmpInst::FCMP_OGT) || (Pred == FCmpInst::FCMP_UGT) ||
+           (Pred == FCmpInst::FCMP_OLE) || (Pred == FCmpInst::FCMP_ULE))
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arsenm wrote:

Don't need parentheses around all these == expressions 

https://github.com/llvm/llvm-project/pull/99475