Rollup merge of rust-lang#47541 - psumbera:master, r=eddyb

Fixes sparc64 cabi fixes.

Argument up to 16 bytes size is provided in registers.
Return value up to 32 bytes size is stored in registers.

Fixes: rust-lang#46679

---

Firefox now (almost) build on sparc. Original rust issue seems to be gone. Note that I'm not rust expert and the fix was suggested in bug.

src/librustc_trans/cabi_sparc64.rs

@@ -50,7 +50,7 @@ fn classify_ret_ty<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>, ret: &mut ArgType<'tcx>)
     }
     let size = ret.layout.size;
     let bits = size.bits();
-    if bits <= 128 {
+    if bits <= 256 {
         let unit = if bits <= 8 {
             Reg::i8()
         } else if bits <= 16 {
@@ -84,6 +84,11 @@ fn classify_arg_ty<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>, arg: &mut ArgType<'tcx>)
     }
 
     let total = arg.layout.size;
+    if total.bits() > 128 {
+        arg.make_indirect();
+        return;
+    }
+
     arg.cast_to(Uniform {
         unit: Reg::i64(),
         total