diff --git a/cranelift/codegen/src/machinst/abi.rs b/cranelift/codegen/src/machinst/abi.rs
index bbff4abeca..e51a636145 100644
--- a/cranelift/codegen/src/machinst/abi.rs
+++ b/cranelift/codegen/src/machinst/abi.rs
@@ -561,7 +561,7 @@ pub struct Sig(u32);
 cranelift_entity::entity_impl!(Sig);
 
 /// ABI information shared between body (callee) and caller.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct SigData {
     /// Argument locations (regs or stack slots). Stack offsets are relative to
     /// SP on entry to function.
@@ -669,10 +669,17 @@ impl SigData {
         // regs, which we will remove from the clobber set below.
         let mut clobbers = M::get_regs_clobbered_by_call(self.call_conv);
 
-        // Compute defs: all retval regs, and all caller-save (clobbered) regs.
+        // Compute defs: all retval regs, and all caller-save
+        // (clobbered) regs, except for StructRet args.
         let mut defs = smallvec![];
         for ret in &self.rets {
-            if let &ABIArg::Slots { ref slots, .. } = ret {
+            if let &ABIArg::Slots {
+                ref slots, purpose, ..
+            } = ret
+            {
+                if purpose == ir::ArgumentPurpose::StructReturn {
+                    continue;
+                }
                 for slot in slots {
                     match slot {
                         &ABIArgSlot::Reg { reg, .. } => {
@@ -694,9 +701,17 @@ impl SigData {
         // regs, which we will remove from the clobber set below.
         let mut clobbers = M::get_regs_clobbered_by_call(self.call_conv);
 
-        // Remove retval regs from clobbers.
+        // Remove retval regs from clobbers. Skip StructRets: these
+        // are not, semantically, returns at the CLIF level, so we
+        // treat such a value as a clobber instead.
         for ret in &self.rets {
-            if let &ABIArg::Slots { ref slots, .. } = ret {
+            if let &ABIArg::Slots {
+                ref slots, purpose, ..
+            } = ret
+            {
+                if purpose == ir::ArgumentPurpose::StructReturn {
+                    continue;
+                }
                 for slot in slots {
                     match slot {
                         &ABIArgSlot::Reg { reg, .. } => {
diff --git a/cranelift/codegen/src/machinst/isle.rs b/cranelift/codegen/src/machinst/isle.rs
index 119727e571..8781d8372d 100644
--- a/cranelift/codegen/src/machinst/isle.rs
+++ b/cranelift/codegen/src/machinst/isle.rs
@@ -1206,13 +1206,22 @@ macro_rules! isle_prelude_method_helpers {
                     self.lower_ctx.emit(inst);
                 }
             }
+
             // Handle retvals prior to emitting call, so the
             // constraints are on the call instruction; but buffer the
             // instructions till after the call.
             let mut outputs = InstOutput::new();
             let mut retval_insts: crate::machinst::abi::SmallInstVec<_> = smallvec::smallvec![];
-            for i in 0..num_rets {
-                let ret = self.lower_ctx.sigs()[abi].get_ret(i);
+            // We take the *last* `num_rets` returns of the sig:
+            // this skips a StructReturn, if any, that is present.
+            let sigdata = &self.lower_ctx.sigs()[abi];
+            debug_assert!(num_rets <= sigdata.num_rets());
+            for i in (sigdata.num_rets() - num_rets)..sigdata.num_rets() {
+                // Borrow `sigdata` again so we don't hold a `self`
+                // borrow across the `&mut self` arg to
+                // `abi_arg_slot_regs()` below.
+                let sigdata = &self.lower_ctx.sigs()[abi];
+                let ret = sigdata.get_ret(i);
                 let retval_regs = self.abi_arg_slot_regs(&ret).unwrap();
                 retval_insts.extend(
                     caller
diff --git a/cranelift/filetests/filetests/isa/aarch64/call.clif b/cranelift/filetests/filetests/isa/aarch64/call.clif
index 64ea276ae3..add90de40e 100644
--- a/cranelift/filetests/filetests/isa/aarch64/call.clif
+++ b/cranelift/filetests/filetests/isa/aarch64/call.clif
@@ -475,7 +475,6 @@ block0(v0: i64):
 ;   mov x8, x0
 ;   ldr x4, 8 ; b 12 ; data TestCase(%g) + 0
 ;   blr x4
-;   mov x0, x8
 ;   ldp fp, lr, [sp], #16
 ;   ret
 
diff --git a/cranelift/filetests/filetests/isa/x64/struct-ret.clif b/cranelift/filetests/filetests/isa/x64/struct-ret.clif
index b1fa7ede30..a502546ce4 100644
--- a/cranelift/filetests/filetests/isa/x64/struct-ret.clif
+++ b/cranelift/filetests/filetests/isa/x64/struct-ret.clif
@@ -33,6 +33,7 @@ block0(v0: i64, v1: i64):
 ;   movq    %rsi, %rdi
 ;   load_ext_name %f2+0, %r8
 ;   call    *%r8
+;   movq    %rdx, %rax
 ;   movq    %rbp, %rsp
 ;   popq    %rbp
 ;   ret
@@ -47,10 +48,15 @@ block0(v0: i64):
 
 ;   pushq   %rbp
 ;   movq    %rsp, %rbp
+;   subq    %rsp, $16, %rsp
+;   movq    %r15, 0(%rsp)
 ; block0:
-;   movq    %rdi, %rax
+;   movq    %rdi, %r15
 ;   load_ext_name %f4+0, %rdx
 ;   call    *%rdx
+;   movq    %r15, %rax
+;   movq    0(%rsp), %r15
+;   addq    %rsp, $16, %rsp
 ;   movq    %rbp, %rsp
 ;   popq    %rbp
 ;   ret