diff --git a/cranelift/codegen/meta/src/shared/legalize.rs b/cranelift/codegen/meta/src/shared/legalize.rs
index 9588272709..1c2c510460 100644
--- a/cranelift/codegen/meta/src/shared/legalize.rs
+++ b/cranelift/codegen/meta/src/shared/legalize.rs
@@ -188,6 +188,10 @@ pub(crate) fn define(insts: &InstructionGroup, imm: &Immediates) -> TransformGro
     narrow.custom_legalize(load, "narrow_load");
     narrow.custom_legalize(store, "narrow_store");
 
+    // iconst.i64 can't be legalized in the meta langage (because integer literals can't be
+    // embedded as part of arguments), so use a custom legalization for now.
+    narrow.custom_legalize(iconst, "narrow_iconst");
+
     narrow.legalize(
         def!(a = iadd(x, y)),
         vec![
diff --git a/cranelift/codegen/src/legalizer/mod.rs b/cranelift/codegen/src/legalizer/mod.rs
index 0f24689d8c..2fd353c7b9 100644
--- a/cranelift/codegen/src/legalizer/mod.rs
+++ b/cranelift/codegen/src/legalizer/mod.rs
@@ -16,7 +16,7 @@
 use crate::bitset::BitSet;
 use crate::cursor::{Cursor, FuncCursor};
 use crate::flowgraph::ControlFlowGraph;
-use crate::ir::types::I32;
+use crate::ir::types::{I32, I64};
 use crate::ir::{self, InstBuilder, MemFlags};
 use crate::isa::TargetIsa;
 use crate::predicates;
@@ -633,3 +633,35 @@ fn narrow_store(
     );
     pos.remove_inst();
 }
+
+/// Expands an illegal iconst value by splitting it into two.
+fn narrow_iconst(
+    inst: ir::Inst,
+    func: &mut ir::Function,
+    _cfg: &mut ControlFlowGraph,
+    isa: &dyn TargetIsa,
+) {
+    let imm: i64 = if let ir::InstructionData::UnaryImm {
+        opcode: ir::Opcode::Iconst,
+        imm,
+    } = &func.dfg[inst]
+    {
+        (*imm).into()
+    } else {
+        panic!("unexpected instruction in narrow_iconst");
+    };
+
+    let mut pos = FuncCursor::new(func).at_inst(inst);
+    pos.use_srcloc(inst);
+
+    let ty = pos.func.dfg.ctrl_typevar(inst);
+    if isa.pointer_bits() == 32 && ty == I64 {
+        let low = pos.ins().iconst(I32, imm & 0xffffffff);
+        let high = pos.ins().iconst(I32, imm >> 32);
+        // The instruction has as many results as iconcat, so no need to replace them.
+        pos.func.dfg.replace(inst).iconcat(low, high);
+        return;
+    }
+
+    unimplemented!("missing encoding or legalization for iconst.{:?}", ty);
+}
diff --git a/cranelift/filetests/filetests/isa/x86/legalize-custom.clif b/cranelift/filetests/filetests/isa/x86/legalize-custom.clif
index 747f4e819b..2657bfd497 100644
--- a/cranelift/filetests/filetests/isa/x86/legalize-custom.clif
+++ b/cranelift/filetests/filetests/isa/x86/legalize-custom.clif
@@ -62,14 +62,6 @@ ebb0:
     return v1
 }
 
-function %f64const() -> f64 {
-ebb0:
-    v1 = f64const 0x1.0p1
-    ; check: $(tmp=$V) = iconst.i64
-    ; check: v1 = bitcast.f64 $tmp
-    return v1
-}
-
 function %select_f64(f64, f64, i32) -> f64 {
 ebb0(v0: f64, v1: f64, v2: i32):
     v3 = select v2, v0, v1
diff --git a/cranelift/filetests/filetests/isa/x86/legalize-f64const-x64.clif b/cranelift/filetests/filetests/isa/x86/legalize-f64const-x64.clif
new file mode 100644
index 0000000000..addafe90a3
--- /dev/null
+++ b/cranelift/filetests/filetests/isa/x86/legalize-f64const-x64.clif
@@ -0,0 +1,13 @@
+; Test the legalization of f64const.
+test legalizer
+target x86_64
+
+; regex: V=v\d+
+
+function %f64const() -> f64 {
+ebb0:
+    v1 = f64const 0x1.0p1
+    ; check: $(tmp=$V) = iconst.i64
+    ; check: v1 = bitcast.f64 $tmp
+    return v1
+}
diff --git a/cranelift/filetests/filetests/legalizer/iconst-i64.clif b/cranelift/filetests/filetests/legalizer/iconst-i64.clif
new file mode 100644
index 0000000000..a3c9168416
--- /dev/null
+++ b/cranelift/filetests/filetests/legalizer/iconst-i64.clif
@@ -0,0 +1,12 @@
+test legalizer
+target i686
+
+function %foo() -> i64 {
+ebb0:
+    v1 = iconst.i64 0x6400000042
+    return v1
+}
+
+; check: v2 = iconst.i32 66
+; check: v3 = iconst.i32 100
+; check: v1 = iconcat v2, v3