Pass big aggregated arguments indirectly.

Ensures that arguments of any type can be passed through
`classify_arg_ty()`. Previously any aggregated argument
with a size above the maximum of `MAX_ARG_IN_REGS_SIZE`
triggered the `stack_required` assertion.

The reason was that that the flag directly depends on the
calculated amount of required registered which is not
determined if a given argument is bigger than the expected
maximum of `MAX_ARG_IN_REGS_SIZE`.

Author: 0ndorio

src/librustc_target/abi/call/xtensa.rs

@@ -20,18 +20,22 @@ fn classify_arg_ty<Ty>(arg: &mut ArgType<'_, Ty>, xlen: u64, remaining_gpr: &mut
     // according to the ABI. 2*XLen-aligned varargs are passed in "aligned"
     // register pairs, so may consume 3 registers.
 
-    let mut stack_required = false;
     let arg_size = arg.layout.size;
-    let alignment = arg.layout.details.align.abi;
-
+    if arg_size.bits() > MAX_ARG_IN_REGS_SIZE {
+        arg.make_indirect();
+        return;
+    }
 
+    let alignment = arg.layout.details.align.abi;
     let mut required_gpr = 1u64; // at least one per arg
+
     if alignment.bits() == 2 * xlen {
         required_gpr = 2 + (*remaining_gpr % 2);
     } else if  arg_size.bits() > xlen && arg_size.bits() <= MAX_ARG_IN_REGS_SIZE {
         required_gpr = (arg_size.bits() + (xlen - 1)) / xlen;
     }
 
+    let mut stack_required = false;
     if required_gpr > *remaining_gpr {
         stack_required = true;
         required_gpr = *remaining_gpr;