diff --git a/cranelift/codegen/meta/src/isa/x86/encodings.rs b/cranelift/codegen/meta/src/isa/x86/encodings.rs
index fd160e3e21..7e9f74475e 100644
--- a/cranelift/codegen/meta/src/isa/x86/encodings.rs
+++ b/cranelift/codegen/meta/src/isa/x86/encodings.rs
@@ -1795,14 +1795,14 @@ fn define_simd(
 
         let is_zero_128bit =
             InstructionPredicate::new_is_all_zeroes(&*formats.unary_const, "constant_handle");
-        let template = rec_vconst_optimized.nonrex().opcodes(&PXOR);
+        let template = rec_vconst_optimized.opcodes(&PXOR).infer_rex();
         e.enc_32_64_func(instruction.clone(), template, |builder| {
             builder.inst_predicate(is_zero_128bit)
         });
 
         let is_ones_128bit =
             InstructionPredicate::new_is_all_ones(&*formats.unary_const, "constant_handle");
-        let template = rec_vconst_optimized.nonrex().opcodes(&PCMPEQB);
+        let template = rec_vconst_optimized.opcodes(&PCMPEQB).infer_rex();
         e.enc_32_64_func(instruction, template, |builder| {
             builder.inst_predicate(is_ones_128bit)
         });
@@ -1816,7 +1816,7 @@ fn define_simd(
     // in memory) but some performance measurements are needed.
     for ty in ValueType::all_lane_types().filter(allowed_simd_type) {
         let instruction = vconst.bind(vector(ty, sse_vector_size));
-        let template = rec_vconst.nonrex().opcodes(&MOVUPS_LOAD);
+        let template = rec_vconst.opcodes(&MOVUPS_LOAD).infer_rex();
         e.enc_32_64_maybe_isap(instruction, template, None); // from SSE
     }
 
@@ -1826,7 +1826,10 @@ fn define_simd(
     for ty in ValueType::all_lane_types().filter(allowed_simd_type) {
         // Store
         let bound_store = store.bind(vector(ty, sse_vector_size)).bind(Any);
-        e.enc_32_64(bound_store.clone(), rec_fst.opcodes(&MOVUPS_STORE));
+        e.enc_32_64(
+            bound_store.clone(),
+            rec_fst.opcodes(&MOVUPS_STORE).infer_rex(),
+        );
         e.enc_32_64(bound_store.clone(), rec_fstDisp8.opcodes(&MOVUPS_STORE));
         e.enc_32_64(bound_store, rec_fstDisp32.opcodes(&MOVUPS_STORE));
 
diff --git a/cranelift/codegen/meta/src/isa/x86/recipes.rs b/cranelift/codegen/meta/src/isa/x86/recipes.rs
index c512e98467..c9794a02da 100644
--- a/cranelift/codegen/meta/src/isa/x86/recipes.rs
+++ b/cranelift/codegen/meta/src/isa/x86/recipes.rs
@@ -46,6 +46,16 @@ impl<'builder> RecipeGroup<'builder> {
         self.templates.push(template.clone());
         template
     }
+    fn add_template_inferred(
+        &mut self,
+        recipe: EncodingRecipeBuilder,
+        infer_function: &'static str,
+    ) -> Rc<Template<'builder>> {
+        let template =
+            Rc::new(Template::new(recipe, self.regs).inferred_rex_compute_size(infer_function));
+        self.templates.push(template.clone());
+        template
+    }
     fn add_template(&mut self, template: Template<'builder>) -> Rc<Template<'builder>> {
         let template = Rc::new(template);
         self.templates.push(template.clone());
@@ -1481,7 +1491,7 @@ pub(crate) fn define<'shared>(
         );
 
         // XX /r register-indirect store of FPR with no offset.
-        recipes.add_template_recipe(
+        recipes.add_template_inferred(
             EncodingRecipeBuilder::new("fst", &formats.store, 1)
                 .operands_in(vec![fpr, gpr])
                 .inst_predicate(has_no_offset)
@@ -1504,6 +1514,7 @@ pub(crate) fn define<'shared>(
                         }
                     "#,
                 ),
+            "size_plus_maybe_sib_or_offset_inreg1_plus_rex_prefix_for_inreg0_inreg1",
         );
 
         let has_small_offset =
@@ -2515,7 +2526,7 @@ pub(crate) fn define<'shared>(
             ),
     );
 
-    recipes.add_template_recipe(
+    recipes.add_template_inferred(
         EncodingRecipeBuilder::new("vconst", &formats.unary_const, 5)
             .operands_out(vec![fpr])
             .clobbers_flags(false)
@@ -2526,9 +2537,10 @@ pub(crate) fn define<'shared>(
                     const_disp4(constant_handle, func, sink);
                 "#,
             ),
+        "size_with_inferred_rex_for_outreg0",
     );
 
-    recipes.add_template_recipe(
+    recipes.add_template_inferred(
         EncodingRecipeBuilder::new("vconst_optimized", &formats.unary_const, 1)
             .operands_out(vec![fpr])
             .clobbers_flags(false)
@@ -2538,6 +2550,7 @@ pub(crate) fn define<'shared>(
                     modrm_rr(out_reg0, out_reg0, sink);
                 "#,
             ),
+        "size_with_inferred_rex_for_outreg0",
     );
 
     recipes.add_template_recipe(
diff --git a/cranelift/codegen/src/isa/x86/enc_tables.rs b/cranelift/codegen/src/isa/x86/enc_tables.rs
index a93be1d658..27f7ed43db 100644
--- a/cranelift/codegen/src/isa/x86/enc_tables.rs
+++ b/cranelift/codegen/src/isa/x86/enc_tables.rs
@@ -123,6 +123,22 @@ fn size_plus_maybe_sib_or_offset_for_inreg_1(
     sizing.base_size + if needs_sib_or_offset { 1 } else { 0 }
 }
 
+/// Calculates the size while inferring if the first and second input registers (inreg0, inreg1)
+/// require a dynamic REX prefix and if the second input register (inreg1) requires a SIB or offset.
+fn size_plus_maybe_sib_or_offset_inreg1_plus_rex_prefix_for_inreg0_inreg1(
+    sizing: &RecipeSizing,
+    enc: Encoding,
+    inst: Inst,
+    divert: &RegDiversions,
+    func: &Function,
+) -> u8 {
+    let needs_rex = (EncodingBits::from(enc.bits()).rex_w() != 0)
+        || test_input(0, inst, divert, func, is_extended_reg)
+        || test_input(1, inst, divert, func, is_extended_reg);
+    size_plus_maybe_sib_or_offset_for_inreg_1(sizing, enc, inst, divert, func)
+        + if needs_rex { 1 } else { 0 }
+}
+
 /// Infers whether a dynamic REX prefix will be emitted, for use with one input reg.
 ///
 /// A REX prefix is known to be emitted if either:
@@ -199,6 +215,19 @@ fn size_with_inferred_rex_for_inreg0_outreg0(
     sizing.base_size + if needs_rex { 1 } else { 0 }
 }
 
+/// Infers whether a dynamic REX prefix will be emitted, based on a single output register.
+fn size_with_inferred_rex_for_outreg0(
+    sizing: &RecipeSizing,
+    enc: Encoding,
+    inst: Inst,
+    divert: &RegDiversions,
+    func: &Function,
+) -> u8 {
+    let needs_rex = (EncodingBits::from(enc.bits()).rex_w() != 0)
+        || test_result(0, inst, divert, func, is_extended_reg);
+    sizing.base_size + if needs_rex { 1 } else { 0 }
+}
+
 /// Infers whether a dynamic REX prefix will be emitted, for use with CMOV.
 ///
 /// CMOV uses 3 inputs, with the REX is inferred from reg1 and reg2.
diff --git a/cranelift/filetests/filetests/isa/x86/binary64.clif b/cranelift/filetests/filetests/isa/x86/binary64.clif
index 41290d1462..c241d33769 100644
--- a/cranelift/filetests/filetests/isa/x86/binary64.clif
+++ b/cranelift/filetests/filetests/isa/x86/binary64.clif
@@ -1679,3 +1679,11 @@ block0:
     [-, %r10]   v0 = bconst.b64 true    ; bin: 41 ba 00000001
     return
 }
+
+function %V128() {
+block0:
+    [-,%r10]            v3 = iconst.i64 0x2102_0304_f1f2_f3f4 ; bin: 49 ba 21020304f1f2f3f4
+    [-, %xmm9]          v4 = vconst.i32x4 [0 1 2 3]  ; bin: 44 0f 10 0d 00000005 PCRelRodata4(23)
+                        store v4, v3    ; bin: heap_oob 45 0f 11 0a
+                        return
+}