gccrs: add support for lang_item eq and PartialEq trait

The Eq and Partial Ord are very similar to the operator overloads
we support for add/sub/etc... but they differ in that usually the
function call name matches the name of the lang item. This time
we need to have support to send in a new path for the method call
on the lang item we want instead of just the name of the lang item.

NOTE: this test case doesnt work correctly yet we need to support
the derive of partial eq on enums to generate the correct comparison
code for that.

Fixes Rust-GCC#3302

gcc/rust/ChangeLog:

	* backend/rust-compile-expr.cc (CompileExpr::visit): handle partial_eq possible call
	* backend/rust-compile-expr.h: handle case where lang item calls differ from name
	* hir/tree/rust-hir-expr.cc (OperatorExprMeta::OperatorExprMeta): new helper
	* hir/tree/rust-hir-expr.h: likewise
	* typecheck/rust-hir-type-check-expr.cc (TypeCheckExpr::visit): handle partial_eq
	(TypeCheckExpr::resolve_operator_overload): likewise
	* typecheck/rust-hir-type-check-expr.h: likewise
	* util/rust-lang-item.cc (LangItem::ComparisonToLangItem): map comparison to lang item
	(LangItem::ComparisonToSegment): likewise
	* util/rust-lang-item.h: new lang items PartialOrd and Eq
	* util/rust-operators.h (enum class): likewise

gcc/testsuite/ChangeLog:

	* rust/compile/nr2/exclude: nr2 cant handle this
	* rust/compile/cmp1.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>

1 files changed, 44 insertions, 0 deletions

diff --git a/gcc/rust/util/rust-lang-item.cc b/gcc/rust/util/rust-lang-item.cc
index c4c1d1c..4a60909 100644
--- a/gcc/rust/util/rust-lang-item.cc
+++ b/gcc/rust/util/rust-lang-item.cc
@@ -98,6 +98,9 @@ const BiMap<std::string, LangItem::Kind> Rust::LangItem::lang_items = {{
 
   {"into_iter", Kind::INTOITER_INTOITER},
   {"next", Kind::ITERATOR_NEXT},
+
+  {"eq", Kind::EQ},
+  {"partial_ord", Kind::PARTIAL_ORD},
 }};
 
 tl::optional<LangItem::Kind>
@@ -146,6 +149,47 @@ LangItem::OperatorToLangItem (ArithmeticOrLogicalOperator op)
 }
 
 LangItem::Kind
+LangItem::ComparisonToLangItem (ComparisonOperator op)
+{
+  switch (op)
+    {
+    case ComparisonOperator::NOT_EQUAL:
+    case ComparisonOperator::EQUAL:
+      return LangItem::Kind::EQ;
+
+    case ComparisonOperator::GREATER_THAN:
+    case ComparisonOperator::LESS_THAN:
+    case ComparisonOperator::GREATER_OR_EQUAL:
+    case ComparisonOperator::LESS_OR_EQUAL:
+      return LangItem::Kind::PARTIAL_ORD;
+    }
+
+  rust_unreachable ();
+}
+
+std::string
+LangItem::ComparisonToSegment (ComparisonOperator op)
+{
+  switch (op)
+    {
+    case ComparisonOperator::NOT_EQUAL:
+      return "ne";
+    case ComparisonOperator::EQUAL:
+      return "eq";
+    case ComparisonOperator::GREATER_THAN:
+      return "gt";
+    case ComparisonOperator::LESS_THAN:
+      return "lt";
+    case ComparisonOperator::GREATER_OR_EQUAL:
+      return "ge";
+    case ComparisonOperator::LESS_OR_EQUAL:
+      return "le";
+    }
+
+  rust_unreachable ();
+}
+
+LangItem::Kind
 LangItem::CompoundAssignmentOperatorToLangItem (ArithmeticOrLogicalOperator op)
 {
   switch (op)