[llvm] [InstCombine] Fold fcmp ogt (x - y), 0 into fcmp ogt x, y #85245 (PR #85506)

[Matt Arsenault via llvm-commits]

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@@ -7972,6 +7972,11 @@ Instruction *InstCombinerImpl::visitFCmpInst(FCmpInst &I) {
   Constant *RHSC;
   if (match(Op0, m_Instruction(LHSI)) && match(Op1, m_Constant(RHSC))) {
     switch (LHSI->getOpcode()) {
+    case Instruction::FSub:
+      if (Pred == FCmpInst::FCMP_OGT && match(RHSC, m_PosZeroFP()) &&
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arsenm wrote:

https://github.com/llvm/llvm-project/blob/6f44bb7717897191be25aa01161831c67cdf5b84/llvm/include/llvm/Analysis/ValueTracking.h#L511 is the helper I was thinking of. It's 1 level below isKnownNeverInfinity, but can be used the same way 

https://github.com/llvm/llvm-project/pull/85506