Support predicate registers (clobber-only) in Hexagon inline assembly

Author: taiki-e

src/asm.rs

@@ -634,6 +634,9 @@ fn reg_to_gcc(reg: InlineAsmRegOrRegClass) -> ConstraintOrRegister {
             InlineAsmRegClass::Bpf(BpfInlineAsmRegClass::reg) => "r",
             InlineAsmRegClass::Bpf(BpfInlineAsmRegClass::wreg) => "w",
             InlineAsmRegClass::Hexagon(HexagonInlineAsmRegClass::reg) => "r",
+            InlineAsmRegClass::Hexagon(HexagonInlineAsmRegClass::preg) => {
+                unreachable!("clobber-only")
+            }
             InlineAsmRegClass::LoongArch(LoongArchInlineAsmRegClass::reg) => "r",
             InlineAsmRegClass::LoongArch(LoongArchInlineAsmRegClass::freg) => "f",
             InlineAsmRegClass::M68k(M68kInlineAsmRegClass::reg) => "r",
@@ -720,6 +723,9 @@ fn dummy_output_type<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, reg: InlineAsmRegCl
             cx.type_vector(cx.type_i64(), 2)
         }
         InlineAsmRegClass::Hexagon(HexagonInlineAsmRegClass::reg) => cx.type_i32(),
+        InlineAsmRegClass::Hexagon(HexagonInlineAsmRegClass::preg) => {
+            unreachable!("clobber-only")
+        }
         InlineAsmRegClass::LoongArch(LoongArchInlineAsmRegClass::reg) => cx.type_i32(),
         InlineAsmRegClass::LoongArch(LoongArchInlineAsmRegClass::freg) => cx.type_f32(),
         InlineAsmRegClass::Mips(MipsInlineAsmRegClass::reg) => cx.type_i32(),