[llvm] IVDesc: unify RecurKinds IAnyOf and FAnyOf (PR #118393)

[David Sherwood via llvm-commits]

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@@ -209,7 +207,9 @@ class RecurrenceDescriptor {
 
   RecurKind getRecurrenceKind() const { return Kind; }
 
-  unsigned getOpcode() const { return getOpcode(getRecurrenceKind()); }
+  unsigned getOpcode() const {
+    return getOpcode(getRecurrenceKind(), getRecurrenceType());
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david-arm wrote:

Hmm, it's pretty confusing having Instruction::getOpcode and RecurrenceDescriptor::getOpcode. I see now that `isRecurrenceInstr` calls the Instruction version. So if #118777 lands `getOpcode` in this PR will still return the wrong value, but simply won't get called in lib/Analysis/IVDescriptors.cpp. However, `getOpcode` will still be incorrect if called anywhere else and so there will still be a hidden bug in the code. Essentially it looks like the static version of `RecurrenceDescriptor::getOpcode` is returning the opcode at the start of the chain of operations, e.g. RecurKind::SMin returns icmp too rather than the select operation which is at the end. If `getOpcode` requires the type used at the start of the chain, then presumably we should be passing in that type instead?

https://github.com/llvm/llvm-project/pull/118393