[llvm] [Support][KnownFPClass] Refine fdiv and fdiv_self class propagation + some minor fixes for propagateXorSign (PR #215014)

[Max Graey via llvm-commits]

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@@ -2346,8 +2342,7 @@ define nofpclass(nan) half @ret_nonan__unknown__fdiv__zero_or_nan(half %unknown,
 define nofpclass(inf) half @ret_noinf__unknown__fdiv__zero_or_nan(half %unknown, half nofpclass(inf sub norm) %zero.or.nan) {
 ; CHECK-LABEL: define nofpclass(inf) half @ret_noinf__unknown__fdiv__zero_or_nan(
 ; CHECK-SAME: half [[UNKNOWN:%.*]], half nofpclass(inf sub norm) [[ZERO_OR_NAN:%.*]]) {
-; CHECK-NEXT:    [[DIV:%.*]] = fdiv half [[UNKNOWN]], [[ZERO_OR_NAN]]
-; CHECK-NEXT:    ret half [[DIV]]
+; CHECK-NEXT:    ret half +qnan
 ;
   %div = fdiv half %unknown, %zero.or.nan
   ret half %div
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MaxGraey wrote:

proof: https://alive2.llvm.org/ce/z/LxwHEV

https://github.com/llvm/llvm-project/pull/215014