gccrs: Implement compilation support for TuplePatternItems::RANGED

Example GIMPLE output of the match statement for match-restpattern-tuple-1.rs:

...
RUSTTMP.2 = x;
_1 = RUSTTMP.2.__0;
_2 = _1 == 1;
_3 = RUSTTMP.2.__3;
_4 = _3 == 4;
_5 = _2 & _4;
if (_5 != 0) goto <D.109>; else goto <D.110>;
<D.109>:
{
    {

    }
    goto <D.104>;
}
<D.110>:
if (1 != 0) goto <D.111>; else goto <D.112>;
<D.111>:
{
    {

    }
    goto <D.104>;
}
<D.112>:
<D.104>:
...

gcc/rust/ChangeLog:

	* backend/rust-compile-pattern.cc (CompilePatternCheckExpr::visit(TuplePattern)):
		Implement check expression compilation for TuplePatternItems::RANGED.

Signed-off-by: Yap Zhi Heng <yapzhhg@gmail.com>

Author: Polygonalr

gcc/rust/backend/rust-compile-pattern.cc

@@ -430,8 +430,50 @@ CompilePatternCheckExpr::visit (HIR::TuplePattern &pattern)
     {
     case HIR::TuplePatternItems::RANGED:
       {
-	// TODO
-	gcc_unreachable ();
+	auto &items
+	  = static_cast<HIR::TuplePatternItemsRanged &> (pattern.get_items ());
+	size_t tuple_field_index = 0;
+
+	// lookup the type to find out number of fields
+	TyTy::BaseType *ty = nullptr;
+	bool ok = ctx->get_tyctx ()->lookup_type (
+	  pattern.get_mappings ().get_hirid (), &ty);
+	rust_assert (ok);
+	rust_assert (ty->get_kind () == TyTy::TypeKind::TUPLE);
+
+	// compile check expr for lower patterns
+	for (auto &pat : items.get_lower_patterns ())
+	  {
+	    tree field_expr
+	      = Backend::struct_field_expression (match_scrutinee_expr,
+						  tuple_field_index++,
+						  pat->get_locus ());
+
+	    tree check_expr_sub
+	      = CompilePatternCheckExpr::Compile (*pat, field_expr, ctx);
+	    check_expr = Backend::arithmetic_or_logical_expression (
+	      ArithmeticOrLogicalOperator::BITWISE_AND, check_expr,
+	      check_expr_sub, pat->get_locus ());
+	  }
+
+	// skip the fields that are not checked
+	tuple_field_index = static_cast<TyTy::TupleType &> (*ty).num_fields ()
+			    - items.get_upper_patterns ().size ();
+
+	// compile check expr for upper patterns
+	for (auto &pat : items.get_upper_patterns ())
+	  {
+	    tree field_expr
+	      = Backend::struct_field_expression (match_scrutinee_expr,
+						  tuple_field_index++,
+						  pat->get_locus ());
+
+	    tree check_expr_sub
+	      = CompilePatternCheckExpr::Compile (*pat, field_expr, ctx);
+	    check_expr = Backend::arithmetic_or_logical_expression (
+	      ArithmeticOrLogicalOperator::BITWISE_AND, check_expr,
+	      check_expr_sub, pat->get_locus ());
+	  }
       }
       break;
 

gcc/testsuite/rust/compile/match-restpattern-tuple-1.rs

@@ -0,0 +1,8 @@
+fn main() {
+    let x = (1, 2, 3, 4);
+
+    match x {
+        (1, .., 4) => {},
+        _ => {}
+    }
+}

gcc/testsuite/rust/compile/match-restpattern-tuple-2.rs

@@ -0,0 +1,8 @@
+fn main() {
+    let x = (1, 2, 3, 4);
+
+    match x {
+        (1, .., 2, 3, 4, 5) => {}, // { dg-error "expected a tuple with 4 elements, found one with 5 elements" }
+        _ => {}
+    }
+}

gcc/testsuite/rust/execute/torture/match-restpattern-tuple.rs

@@ -0,0 +1,27 @@
+// { dg-output "correct\r*" }
+extern "C" {
+    fn puts(s: *const i8);
+}
+
+fn main() -> i32 {
+    let x = (1, 2, 3, 4);
+    let mut ret = 1;
+
+    match x {
+        (1, .., 2, 4) => {
+            /* should not take this path */
+            unsafe { puts("wrong\0" as *const str as *const i8) }
+        },
+        (2, ..) => {
+            /* should not take this path */
+            unsafe { puts("wrong\0" as *const str as *const i8) }
+        },
+        (b, .., 4) => { 
+            ret -= b;
+            unsafe { puts("correct\0" as *const str as *const i8) }
+        },
+        _ => {}
+    }
+
+    ret
+}