[wasm-simd][arm][arm64[liftoff] Implement i8x16.popcnt

Bug: v8:11002
Change-Id: I914a7c24828bc53300dc905388741e6939686540
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2676922Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72634}

src/wasm/baseline/arm/liftoff-assembler-arm.h

@@ -3404,7 +3404,7 @@ void LiftoffAssembler::emit_i8x16_shuffle(LiftoffRegister dst,
 
 void LiftoffAssembler::emit_i8x16_popcnt(LiftoffRegister dst,
                                          LiftoffRegister src) {
-  bailout(kSimd, "i8x16.popcnt");
+  vcnt(liftoff::GetSimd128Register(dst), liftoff::GetSimd128Register(src));
 }
 
 void LiftoffAssembler::emit_i8x16_splat(LiftoffRegister dst,

src/wasm/baseline/arm64/liftoff-assembler-arm64.h

@@ -2454,7 +2454,7 @@ void LiftoffAssembler::emit_i8x16_shuffle(LiftoffRegister dst,
 
 void LiftoffAssembler::emit_i8x16_popcnt(LiftoffRegister dst,
                                          LiftoffRegister src) {
-  bailout(kSimd, "i8x16.popcnt");
+  Cnt(dst.fp().V16B(), src.fp().V16B());
 }
 
 void LiftoffAssembler::emit_i8x16_splat(LiftoffRegister dst,