Add x86 SIMD vany_true and x86_ptest

In order to implement SIMD's any_true (https://github.com/WebAssembly/simd/blob/master/proposals/simd/SIMD.md#any-lane-true), we must legalize some instruction (I chose `vany_true`) to a sequence of `PTEST` and `SETNZ`. To emit `PTEST` I added the new CLIF instruction `x86_ptest` and used CLIF's `trueif ne` for `SETNZ`.

cranelift/codegen/meta/src/isa/x86/legalize.rs

@@ -55,12 +55,14 @@ pub(crate) fn define(shared: &mut SharedDefinitions, x86_instructions: &Instruct
     let shuffle = insts.by_name("shuffle");
     let srem = insts.by_name("srem");
     let sshr = insts.by_name("sshr");
+    let trueif = insts.by_name("trueif");
     let udiv = insts.by_name("udiv");
     let umulhi = insts.by_name("umulhi");
     let ushr_imm = insts.by_name("ushr_imm");
     let urem = insts.by_name("urem");
     let ushr = insts.by_name("ushr");
     let vconst = insts.by_name("vconst");
+    let vany_true = insts.by_name("vany_true");
 
     let x86_bsf = x86_instructions.by_name("x86_bsf");
     let x86_bsr = x86_instructions.by_name("x86_bsr");
@@ -69,6 +71,7 @@ pub(crate) fn define(shared: &mut SharedDefinitions, x86_instructions: &Instruct
     let x86_psll = x86_instructions.by_name("x86_psll");
     let x86_psra = x86_instructions.by_name("x86_psra");
     let x86_psrl = x86_instructions.by_name("x86_psrl");
+    let x86_ptest = x86_instructions.by_name("x86_ptest");
     let x86_umulx = x86_instructions.by_name("x86_umulx");
     let x86_smulx = x86_instructions.by_name("x86_smulx");
 
@@ -446,6 +449,16 @@ pub(crate) fn define(shared: &mut SharedDefinitions, x86_instructions: &Instruct
         );
     }
 
+    // SIMD vany_true
+    let ne = Literal::enumerator_for(&imm.intcc, "ne");
+    for ty in ValueType::all_lane_types().filter(allowed_simd_type) {
+        let vany_true = vany_true.bind(vector(ty, sse_vector_size));
+        narrow.legalize(
+            def!(y = vany_true(x)),
+            vec![def!(a = x86_ptest(x, x)), def!(y = trueif(ne, a))],
+        );
+    }
+
     narrow.custom_legalize(shuffle, "convert_shuffle");
     narrow.custom_legalize(extractlane, "convert_extractlane");
     narrow.custom_legalize(insertlane, "convert_insertlane");