gccrs: Implement compilation for SlicePattern matching against ArrayType scrutinee

Example GIMPLE output from compiling testsuite/rust/compile/match-pattern-array.rs:

  ...
  a[0] = 0;
  a[1] = 1;
  RUSTTMP.3 = a;
  _1 = RUSTTMP.3[0];
  _2 = _1 == 0;
  _3 = RUSTTMP.3[1];
  _4 = _3 == 1;
  _5 = _2 & _4;
  if (_5 != 0) goto <D.122>; else goto <D.123>;
  <D.122>:
  {
    {

		}
	}
  goto <D.117>;
  }
  <D.123>:
	...

gcc/rust/ChangeLog:

	* rust-backend.h: New size_constant_expression function.
	* rust-gcc.cc: Implementation of size_constant_expression function to generate tree node
		for array access.
	* backend/rust-compile-pattern.h: Remove empty visits for SlicePattern.
	* backend/rust-compile-pattern.cc: Implement SlicePattern check expression & binding
		compilation against ArrayType scrutinee.

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

6 files changed, 127 insertions, 2 deletions

diff --git a/gcc/rust/backend/rust-compile-pattern.cc b/gcc/rust/backend/rust-compile-pattern.cc
index 3351bec..6d889ba 100644
--- a/gcc/rust/backend/rust-compile-pattern.cc
+++ b/gcc/rust/backend/rust-compile-pattern.cc
@@ -514,6 +514,53 @@ CompilePatternCheckExpr::visit (HIR::IdentifierPattern &pattern)
     }
 }
 
+void
+CompilePatternCheckExpr::visit (HIR::SlicePattern &pattern)
+{
+  check_expr = boolean_true_node;
+
+  // lookup the type
+  TyTy::BaseType *lookup = nullptr;
+  bool ok
+    = ctx->get_tyctx ()->lookup_type (pattern.get_mappings ().get_hirid (),
+				      &lookup);
+  rust_assert (ok);
+
+  // pattern must either be ArrayType or SliceType, should be already confirmed
+  // by type checking
+  rust_assert (lookup->get_kind () == TyTy::TypeKind::ARRAY
+	       || lookup->get_kind () == TyTy::TypeKind::SLICE);
+
+  size_t array_element_index = 0;
+  switch (lookup->get_kind ())
+    {
+    case TyTy::TypeKind::ARRAY:
+      for (auto &pattern_member : pattern.get_items ())
+	{
+	  tree array_index_tree
+	    = Backend::size_constant_expression (array_element_index++);
+	  tree element_expr
+	    = Backend::array_index_expression (match_scrutinee_expr,
+					       array_index_tree,
+					       pattern.get_locus ());
+	  tree check_expr_sub
+	    = CompilePatternCheckExpr::Compile (*pattern_member, element_expr,
+						ctx);
+	  check_expr = Backend::arithmetic_or_logical_expression (
+	    ArithmeticOrLogicalOperator::BITWISE_AND, check_expr,
+	    check_expr_sub, pattern.get_locus ());
+	}
+      break;
+    case TyTy::TypeKind::SLICE:
+      rust_sorry_at (
+	pattern.get_locus (),
+	"SlicePattern matching against slices are not yet supported");
+      break;
+    default:
+      rust_unreachable ();
+    }
+}
+
 // setup the bindings
 
 void
@@ -837,6 +884,44 @@ CompilePatternBindings::visit (HIR::TuplePattern &pattern)
     }
 }
 
+void
+CompilePatternBindings::visit (HIR::SlicePattern &pattern)
+{
+  // lookup the type
+  TyTy::BaseType *lookup = nullptr;
+  bool ok
+    = ctx->get_tyctx ()->lookup_type (pattern.get_mappings ().get_hirid (),
+				      &lookup);
+  rust_assert (ok);
+
+  rust_assert (lookup->get_kind () == TyTy::TypeKind::ARRAY
+	       || lookup->get_kind () == TyTy::TypeKind::SLICE);
+
+  size_t array_element_index = 0;
+  switch (lookup->get_kind ())
+    {
+    case TyTy::TypeKind::ARRAY:
+      for (auto &pattern_member : pattern.get_items ())
+	{
+	  tree array_index_tree
+	    = Backend::size_constant_expression (array_element_index++);
+	  tree element_expr
+	    = Backend::array_index_expression (match_scrutinee_expr,
+					       array_index_tree,
+					       pattern.get_locus ());
+	  CompilePatternBindings::Compile (*pattern_member, element_expr, ctx);
+	}
+      break;
+    case TyTy::TypeKind::SLICE:
+      rust_sorry_at (
+	pattern.get_locus (),
+	"SlicePattern matching against slices are not yet supported");
+      break;
+    default:
+      rust_unreachable ();
+    }
+}
+
 //
 
 void
diff --git a/gcc/rust/backend/rust-compile-pattern.h b/gcc/rust/backend/rust-compile-pattern.h
index 4dd7d55..233799e 100644
--- a/gcc/rust/backend/rust-compile-pattern.h
+++ b/gcc/rust/backend/rust-compile-pattern.h
@@ -46,6 +46,7 @@ public:
   void visit (HIR::TupleStructPattern &) override;
   void visit (HIR::TuplePattern &) override;
   void visit (HIR::IdentifierPattern &) override;
+  void visit (HIR::SlicePattern &) override;
 
   // Always succeeds
   void visit (HIR::WildcardPattern &) override
@@ -55,7 +56,6 @@ public:
 
   // Empty visit for unused Pattern HIR nodes.
   void visit (HIR::QualifiedPathInExpression &) override {}
-  void visit (HIR::SlicePattern &) override {}
 
   CompilePatternCheckExpr (Context *ctx, tree match_scrutinee_expr)
     : HIRCompileBase (ctx), match_scrutinee_expr (match_scrutinee_expr),
@@ -95,6 +95,7 @@ public:
   void visit (HIR::ReferencePattern &pattern) override;
   void visit (HIR::IdentifierPattern &) override;
   void visit (HIR::TuplePattern &pattern) override;
+  void visit (HIR::SlicePattern &) override;
 
   // Empty visit for unused Pattern HIR nodes.
   void visit (HIR::AltPattern &) override {}
@@ -102,7 +103,6 @@ public:
   void visit (HIR::PathInExpression &) override {}
   void visit (HIR::QualifiedPathInExpression &) override {}
   void visit (HIR::RangePattern &) override {}
-  void visit (HIR::SlicePattern &) override {}
   void visit (HIR::WildcardPattern &) override {}
 
 protected:
diff --git a/gcc/rust/rust-backend.h b/gcc/rust/rust-backend.h
index 2d813d9..8a77d96 100644
--- a/gcc/rust/rust-backend.h
+++ b/gcc/rust/rust-backend.h
@@ -176,6 +176,9 @@ tree char_constant_expression (char c);
 // Get a char literal
 tree wchar_constant_expression (wchar_t c);
 
+// Get a size literal
+tree size_constant_expression (size_t val);
+
 // Return an expression for the boolean value VAL.
 tree boolean_constant_expression (bool val);
 
diff --git a/gcc/rust/rust-gcc.cc b/gcc/rust/rust-gcc.cc
index 42cdc6c..c5fda5c 100644
--- a/gcc/rust/rust-gcc.cc
+++ b/gcc/rust/rust-gcc.cc
@@ -818,6 +818,12 @@ char_constant_expression (char c)
   return build_int_cst (char_type_node, c);
 }
 
+tree
+size_constant_expression (size_t val)
+{
+  return size_int (val);
+}
+
 // Make a constant boolean expression.
 
 tree
diff --git a/gcc/testsuite/rust/compile/match-slicepattern-array.rs b/gcc/testsuite/rust/compile/match-slicepattern-array.rs
new file mode 100644
index 0000000..e48ca75
--- /dev/null
+++ b/gcc/testsuite/rust/compile/match-slicepattern-array.rs
@@ -0,0 +1,8 @@
+fn main() {
+    let a = [0, 1];
+
+    match a {
+        [0, 1] => {},
+        _ => {}
+    }
+}
diff --git a/gcc/testsuite/rust/execute/torture/match-slicepattern-array-1.rs b/gcc/testsuite/rust/execute/torture/match-slicepattern-array-1.rs
new file mode 100644
index 0000000..95c55d8
--- /dev/null
+++ b/gcc/testsuite/rust/execute/torture/match-slicepattern-array-1.rs
@@ -0,0 +1,23 @@
+// { dg-output "correct\r*" }
+extern "C" {
+    fn puts(s: *const i8);
+}
+
+fn main() -> i32 {
+    let a = [0, 1];
+    let mut ret = 1;
+
+    match a {
+        [0, 0] => {
+            /* should not take this path */
+            unsafe { puts("wrong\0" as *const str as *const i8) }
+        },
+        [0, b] => {
+            ret -= b;
+            unsafe { puts("correct\0" as *const str as *const i8) }
+        },
+        _ => {}
+    }
+
+    ret
+}