[llvm] [DAG] computeKnownFPClass - Add handling for AssertNoFPClass (PR #190185)

[Simon Pilgrim via llvm-commits]

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@@ -29,3 +29,32 @@ define i1 @sqrt_neginf_v4f32(<4 x float> %a0, ptr %p1) {
   %res = tail call i1 @llvm.is.fpclass.f32(float %elt, i32 4)  ; 0x4 = "neginf"
   ret i1 %res
 }
+
+define i1 @demanded_elts_safe_lane(float %unknown) {
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RKSimon wrote:

These don't appear to do anything - I'd recommend adding tests to riscv instead as x86 currently doesn't support isfpclass so relies on early expansion.

Another good way you could try is (temporarily) disable ISD::AssertNoFPClass in isKnownNeverNaN, see which tests in `ninja check-llvm-codegen` fail and build new tests based off those.

https://github.com/llvm/llvm-project/pull/190185