diff --git a/cranelift/codegen/src/isa/aarch64/abi.rs b/cranelift/codegen/src/isa/aarch64/abi.rs
index 0fcc181aa0..e57866c307 100644
--- a/cranelift/codegen/src/isa/aarch64/abi.rs
+++ b/cranelift/codegen/src/isa/aarch64/abi.rs
@@ -85,7 +85,7 @@ impl ABIMachineSpec for AArch64MachineDeps {
         params: &[ir::AbiParam],
         args_or_rets: ArgsOrRets,
         add_ret_area_ptr: bool,
-    ) -> CodegenResult<(Vec<ABIArg>, i64, Option<usize>)> {
+    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)> {
         let is_apple_cc = call_conv.extends_apple_aarch64();
 
         // See AArch64 ABI (https://github.com/ARM-software/abi-aa/blob/2021Q1/aapcs64/aapcs64.rst#64parameter-passing), sections 6.4.
@@ -105,7 +105,7 @@ impl ABIMachineSpec for AArch64MachineDeps {
         let mut next_xreg = 0;
         let mut next_vreg = 0;
         let mut next_stack: u64 = 0;
-        let mut ret = vec![];
+        let mut ret = ABIArgVec::new();
 
         let (max_per_class_reg_vals, mut remaining_reg_vals) = match args_or_rets {
             ArgsOrRets::Args => (8, 16), // x0-x7 and v0-v7
diff --git a/cranelift/codegen/src/isa/s390x/abi.rs b/cranelift/codegen/src/isa/s390x/abi.rs
index de95a733f2..75ee9557b6 100644
--- a/cranelift/codegen/src/isa/s390x/abi.rs
+++ b/cranelift/codegen/src/isa/s390x/abi.rs
@@ -224,12 +224,12 @@ impl ABIMachineSpec for S390xMachineDeps {
         params: &[ir::AbiParam],
         args_or_rets: ArgsOrRets,
         add_ret_area_ptr: bool,
-    ) -> CodegenResult<(Vec<ABIArg>, i64, Option<usize>)> {
+    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)> {
         let mut next_gpr = 0;
         let mut next_fpr = 0;
         let mut next_vr = 0;
         let mut next_stack: u64 = 0;
-        let mut ret = vec![];
+        let mut ret = ABIArgVec::new();
 
         if args_or_rets == ArgsOrRets::Args {
             next_stack = REG_SAVE_AREA_SIZE as u64;
diff --git a/cranelift/codegen/src/isa/x64/abi.rs b/cranelift/codegen/src/isa/x64/abi.rs
index 616ea12b45..9202e2c82f 100644
--- a/cranelift/codegen/src/isa/x64/abi.rs
+++ b/cranelift/codegen/src/isa/x64/abi.rs
@@ -47,14 +47,14 @@ impl ABIMachineSpec for X64ABIMachineSpec {
         params: &[ir::AbiParam],
         args_or_rets: ArgsOrRets,
         add_ret_area_ptr: bool,
-    ) -> CodegenResult<(Vec<ABIArg>, i64, Option<usize>)> {
+    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)> {
         let is_fastcall = call_conv.extends_windows_fastcall();
 
         let mut next_gpr = 0;
         let mut next_vreg = 0;
         let mut next_stack: u64 = 0;
         let mut next_param_idx = 0; // Fastcall cares about overall param index
-        let mut ret = vec![];
+        let mut ret = ABIArgVec::new();
 
         if args_or_rets == ArgsOrRets::Args && is_fastcall {
             // Fastcall always reserves 32 bytes of shadow space corresponding to
diff --git a/cranelift/codegen/src/machinst/abi_impl.rs b/cranelift/codegen/src/machinst/abi_impl.rs
index 203efe78cd..dd2e860386 100644
--- a/cranelift/codegen/src/machinst/abi_impl.rs
+++ b/cranelift/codegen/src/machinst/abi_impl.rs
@@ -310,7 +310,7 @@ pub trait ABIMachineSpec {
         params: &[ir::AbiParam],
         args_or_rets: ArgsOrRets,
         add_ret_area_ptr: bool,
-    ) -> CodegenResult<(Vec<ABIArg>, i64, Option<usize>)>;
+    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)>;
 
     /// Returns the offset from FP to the argument area, i.e., jumping over the saved FP, return
     /// address, and maybe other standard elements depending on ABI (e.g. Wasm TLS reg).
@@ -499,15 +499,18 @@ pub trait ABIMachineSpec {
     ) -> ir::ArgumentExtension;
 }
 
+// A vector of `ABIArg`s with inline capacity, since they are typically small.
+pub type ABIArgVec = SmallVec<[ABIArg; 6]>;
+
 /// ABI information shared between body (callee) and caller.
 #[derive(Clone)]
 pub struct ABISig {
     /// Argument locations (regs or stack slots). Stack offsets are relative to
     /// SP on entry to function.
-    args: Vec<ABIArg>,
+    args: ABIArgVec,
     /// Return-value locations. Stack offsets are relative to the return-area
     /// pointer.
-    rets: Vec<ABIArg>,
+    rets: ABIArgVec,
     /// Space on stack used to store arguments.
     sized_stack_arg_space: i64,
     /// Space on stack used to store return values.