[llvm] Optimize count leading ones if promoted type (PR #99591)

[via llvm-commits]

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@@ -2624,6 +2624,58 @@ define <vscale x 1 x i9> @vp_ctlz_zero_undef_nxv1i9(<vscale x 1 x i9> %va, <vsca
   %v = call <vscale x 1 x i9> @llvm.vp.ctlz.nxv1i9(<vscale x 1 x i9> %va, i1 true, <vscale x 1 x i1> %m, i32 %evl)
   ret <vscale x 1 x i9> %v
 }
+define <vscale x 1 x i9> @vp_ctlo_nxv1i9(<vscale x 1 x i9> %va, <vscale x 1 x i1> %m, i32 zeroext %evl) {
+; CHECK-LABEL: vp_ctlo_nxv1i9:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetvli zero, a0, e16, mf4, ta, ma
+; CHECK-NEXT:    vsll.vi v8, v8, 7, v0.t
+; CHECK-NEXT:    vnot.v v8, v8, v0.t
+; CHECK-NEXT:    vfwcvt.f.xu.v v9, v8, v0.t
+; CHECK-NEXT:    vsetvli zero, zero, e32, mf2, ta, ma
+; CHECK-NEXT:    vsrl.vi v8, v9, 23, v0.t
+; CHECK-NEXT:    vsetvli zero, zero, e16, mf4, ta, ma
+; CHECK-NEXT:    vnsrl.wi v8, v8, 0, v0.t
+; CHECK-NEXT:    li a0, 142
+; CHECK-NEXT:    vrsub.vx v8, v8, a0, v0.t
+; CHECK-NEXT:    ret
+;
+; CHECK-ZVBB-LABEL: vp_ctlo_nxv1i9:
+; CHECK-ZVBB:       # %bb.0:
+; CHECK-ZVBB-NEXT:    vsetvli zero, a0, e16, mf4, ta, ma
+; CHECK-ZVBB-NEXT:    vsll.vi v8, v8, 7, v0.t
+; CHECK-ZVBB-NEXT:    vnot.v v8, v8, v0.t
+; CHECK-ZVBB-NEXT:    vclz.v v8, v8, v0.t
+; CHECK-ZVBB-NEXT:    ret
+  %va.not = xor <vscale x 1 x i9> %va, splat (i9 -1)
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v01dXYZ wrote:

Maybe you want me to not try to match `VP_CTLZ + XOR` and only keep `VP_CTLZ + VP_XOR`. 

https://github.com/llvm/llvm-project/pull/99591