machinst ABI: Pass fixed frame size to gen_clobber_restore

The ABI common code currently passes the fixed frame size to
the gen_clobber_save back-end routine, which is required to
emit code to allocate the required stack space in the prologue.

Similarly, the back-end needs to emit code to de-allocate the
stack in the epilogue.  However, at this point the back-end
does not have access to that fixed frame size value any more.
With targets that use a frame pointer, this does not matter,
since de-allocation can be done simply by assigning the frame
pointer back to the stack pointer.  However, on targets that
do not use a frame pointer, the frame size is required.

To allow back-ends that option, this patch changes ABI common
code to pass the fixed frame size to get_clobber_restore as
well (the same value as is passed to get_clobber_save).

cranelift/codegen/src/isa/aarch64/abi.rs

@@ -559,6 +559,7 @@ impl ABIMachineSpec for AArch64MachineDeps {
         call_conv: isa::CallConv,
         flags: &settings::Flags,
         clobbers: &Set<Writable<RealReg>>,
+        _fixed_frame_storage_size: u32,
     ) -> SmallVec<[Inst; 16]> {
         let mut insts = SmallVec::new();
         let (clobbered_int, clobbered_vec) = get_regs_saved_in_prologue(call_conv, clobbers);

cranelift/codegen/src/isa/arm32/abi.rs

@@ -336,6 +336,7 @@ impl ABIMachineSpec for Arm32MachineDeps {
         _call_conv: isa::CallConv,
         _flags: &settings::Flags,
         clobbers: &Set<Writable<RealReg>>,
+        _fixed_frame_storage_size: u32,
     ) -> SmallVec<[Inst; 16]> {
         let mut insts = SmallVec::new();
         let clobbered_vec = get_callee_saves(clobbers);

cranelift/codegen/src/isa/x64/abi.rs

@@ -437,6 +437,7 @@ impl ABIMachineSpec for X64ABIMachineSpec {
         call_conv: isa::CallConv,
         flags: &settings::Flags,
         clobbers: &Set<Writable<RealReg>>,
+        _fixed_frame_storage_size: u32,
     ) -> SmallVec<[Self::I; 16]> {
         let mut insts = SmallVec::new();