[llvm] [InstSimplify] Optimize maximumnum and minimumnum (PR #139581)

[Matt Arsenault via llvm-commits]

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@@ -6711,7 +6712,16 @@ Value *llvm::simplifyBinaryIntrinsic(Intrinsic::ID IID, Type *ReturnType,
   case Intrinsic::maxnum:
   case Intrinsic::minnum:
   case Intrinsic::maximum:
-  case Intrinsic::minimum: {
+  case Intrinsic::minimum:
+  case Intrinsic::maximumnum:
+  case Intrinsic::minimumnum: {
+    // In several cases here, we deviate from exact IEEE 754 semantics
+    // to enable optimizations (as allowed by the LLVM IR spec).
+    //
+    // For instance, we often return one of the arguments unmodified instead of
+    // inserting an llvm.canonicalize to transform input sNaNs into qNaNs or to
+    // respect any FTZ semantics, and sometimes assume all NaN inputs are qNaNs.
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arsenm wrote:

Comment is a bit off; FTZ is explicitly non-standard. Maybe just state this may drop a canonicalize 

https://github.com/llvm/llvm-project/pull/139581