From 22e40cc7feb8abda85762e4f07719836d5c57f1a Mon Sep 17 00:00:00 2001
From: Cherry Mui <cherryyz@google.com>
Date: Tue, 3 Aug 2021 19:35:55 -0400
Subject: compiler: support new language constructs in escape analysis

Previous CLs add new language constructs in Go 1.17, specifically,
unsafe.Add, unsafe.Slice, and conversion from a slice to a pointer
to an array. This CL handles them in the escape analysis.

At the point of the escape analysis, unsafe.Add and unsafe.Slice
are still builtin calls, so just handle them in data flow.
Conversion from a slice to a pointer to an array has already been
lowered to a combination of compound expression, conditional
expression and slice info expressions, so handle them in the
escape analysis.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/339671
---
 gcc/go/gofrontend/expressions.h | 75 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)

(limited to 'gcc/go/gofrontend/expressions.h')

diff --git a/gcc/go/gofrontend/expressions.h b/gcc/go/gofrontend/expressions.h
index 492849b..79a8785 100644
--- a/gcc/go/gofrontend/expressions.h
+++ b/gcc/go/gofrontend/expressions.h
@@ -62,6 +62,7 @@ class Type_guard_expression;
 class Heap_expression;
 class Receive_expression;
 class Slice_value_expression;
+class Slice_info_expression;
 class Conditional_expression;
 class Compound_expression;
 class Numeric_constant;
@@ -900,6 +901,14 @@ class Expression
   compound_expression()
   { return this->convert<Compound_expression, EXPRESSION_COMPOUND>(); }
 
+  // If this is a slice info expression, return the
+  // Slice_info_expression structure.  Otherwise, return NULL.
+  Slice_info_expression*
+  slice_info_expression()
+  {
+    return this->convert<Slice_info_expression, EXPRESSION_SLICE_INFO>();
+  }
+
   // Return true if this is a composite literal.
   bool
   is_composite_literal() const;
@@ -4262,6 +4271,60 @@ class Slice_value_expression : public Expression
   Expression* cap_;
 };
 
+// An expression that evaluates to some characteristic of a slice.
+// This is used when indexing, bound-checking, or nil checking a slice.
+
+class Slice_info_expression : public Expression
+{
+ public:
+  Slice_info_expression(Expression* slice, Slice_info slice_info,
+                        Location location)
+    : Expression(EXPRESSION_SLICE_INFO, location),
+      slice_(slice), slice_info_(slice_info)
+  { }
+
+  // The slice operand of this slice info expression.
+  Expression*
+  slice() const
+  { return this->slice_; }
+
+  // The info this expression is about.
+  Slice_info
+  info() const
+  { return this->slice_info_; }
+
+ protected:
+  Type*
+  do_type();
+
+  void
+  do_determine_type(const Type_context*)
+  { }
+
+  Expression*
+  do_copy()
+  {
+    return new Slice_info_expression(this->slice_->copy(), this->slice_info_,
+                                     this->location());
+  }
+
+  Bexpression*
+  do_get_backend(Translate_context* context);
+
+  void
+  do_dump_expression(Ast_dump_context*) const;
+
+  void
+  do_issue_nil_check()
+  { this->slice_->issue_nil_check(); }
+
+ private:
+  // The slice for which we are getting information.
+  Expression* slice_;
+  // What information we want.
+  Slice_info slice_info_;
+};
+
 // Conditional expressions.
 
 class Conditional_expression : public Expression
@@ -4277,6 +4340,14 @@ class Conditional_expression : public Expression
   condition() const
   { return this->cond_; }
 
+  Expression*
+  then_expr() const
+  { return this->then_; }
+
+  Expression*
+  else_expr() const
+  { return this->else_; }
+
  protected:
   int
   do_traverse(Traverse*);
@@ -4322,6 +4393,10 @@ class Compound_expression : public Expression
   init() const
   { return this->init_; }
 
+  Expression*
+  expr() const
+  { return this->expr_; }
+
  protected:
   int
   do_traverse(Traverse*);
-- 
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