Fix 16-bit x86_pextr encoding

The x86 ISA has (at least) two encodings for PEXTRW:
 1. in the SSE2 opcode (66 0f c5) the XMM operand uses r/m and the GPR operand uses reg
 2. in the SSE4.1 opcode (66 0f 3a 15) the XMM operand uses reg and the GPR operand uses r/m

This changes the 16-bit x86_pextr encoding from #1 to #2 to match the other PEXTR* implementations (all #2 style).

Author: abrown

cranelift-codegen/meta/src/isa/x86/encodings.rs

@@ -1909,23 +1909,23 @@ pub(crate) fn define(
     }
 
     // SIMD extractlane
-    let mut x86_pextr_mapping: HashMap<u64, (Vec<u8>, Option<SettingPredicateNumber>)> =
-        HashMap::new();
-    x86_pextr_mapping.insert(8, (vec![0x66, 0x0f, 0x3a, 0x14], Some(use_sse41_simd))); // PEXTRB
-    x86_pextr_mapping.insert(16, (vec![0x66, 0x0f, 0xc5], None)); // PEXTRW from SSE2, SSE4.1 has a PEXTRW that can move to reg/m16 but the opcode is four bytes
-    x86_pextr_mapping.insert(32, (vec![0x66, 0x0f, 0x3a, 0x16], Some(use_sse41_simd))); // PEXTRD
-    x86_pextr_mapping.insert(64, (vec![0x66, 0x0f, 0x3a, 0x16], Some(use_sse41_simd))); // PEXTRQ, only x86_64
+    let mut x86_pextr_mapping: HashMap<u64, Vec<u8>> = HashMap::new();
+    x86_pextr_mapping.insert(8, vec![0x66, 0x0f, 0x3a, 0x14]); // PEXTRB
+    x86_pextr_mapping.insert(16, vec![0x66, 0x0f, 0x3a, 0x15]); // PEXTRW from SSE4.1, SSE2 has a
+                                                                // PEXTRW that can move to reg/m16 but the ModR/M assignment is backwards
+    x86_pextr_mapping.insert(32, vec![0x66, 0x0f, 0x3a, 0x16]); // PEXTRD
+    x86_pextr_mapping.insert(64, vec![0x66, 0x0f, 0x3a, 0x16]); // PEXTRQ, only x86_64
 
     for ty in ValueType::all_lane_types().filter(allowed_simd_type) {
-        if let Some((opcode, isap)) = x86_pextr_mapping.get(&ty.lane_bits()) {
+        if let Some(opcode) = x86_pextr_mapping.get(&ty.lane_bits()) {
             let instruction = x86_pextr.bind_vector_from_lane(ty, sse_vector_size);
             let template = rec_r_ib_unsigned_gpr.opcodes(opcode.clone());
             if ty.lane_bits() < 64 {
-                e.enc_32_64_maybe_isap(instruction, template.nonrex(), isap.clone());
+                e.enc_32_64_maybe_isap(instruction, template.nonrex(), Some(use_sse41_simd));
             } else {
                 // It turns out the 64-bit widths have REX/W encodings and only are available on
                 // x86_64.
-                e.enc64_maybe_isap(instruction, template.rex().w(), isap.clone());
+                e.enc64_maybe_isap(instruction, template.rex().w(), Some(use_sse41_simd));
             }
         }
     }

filetests/isa/x86/extractlane-binemit.clif

@@ -17,7 +17,7 @@ function %test_extractlane_i16() {
 ebb0:
 [-, %rax]   v0 = iconst.i16 4
 [-, %xmm1]  v1 = splat.i16x8 v0
-[-, %rax]   v2 = x86_pextr v1, 4    ; bin: 66 0f c5 c8 04
+[-, %rax]   v2 = x86_pextr v1, 4    ; bin: 66 0f 3a 15 c8 04
             return
 }