From 08c8a26e9ca87ad2dd5b26d397e6107b68adfe76 Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <ian@gcc.gnu.org>
Date: Fri, 3 May 2019 21:45:35 +0000
Subject: compiler: recognize and optimize array range clear

    Recognize

            for i := range a { a[i] = zero }

    for array or slice a, and rewrite it to call memclr, as the gc
    compiler does.

    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/169398

From-SVN: r270862
---
 gcc/go/gofrontend/expressions.h | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

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

diff --git a/gcc/go/gofrontend/expressions.h b/gcc/go/gofrontend/expressions.h
index af7b00c..d2a3472 100644
--- a/gcc/go/gofrontend/expressions.h
+++ b/gcc/go/gofrontend/expressions.h
@@ -544,6 +544,11 @@ class Expression
   is_constant() const
   { return this->do_is_constant(); }
 
+  // Return whether this is the zero value of its type.
+  bool
+  is_zero_value() const
+  { return this->do_is_zero_value(); }
+
   // Return whether this expression can be used as a static
   // initializer.  This is true for an expression that has only
   // numbers and pointers to global variables or composite literals
@@ -1066,6 +1071,11 @@ class Expression
   do_is_constant() const
   { return false; }
 
+  // Return whether this is the zero value of its type.
+  virtual bool
+  do_is_zero_value() const
+  { return false; }
+
   // Return whether this expression can be used as a constant
   // initializer.
   virtual bool
@@ -1600,6 +1610,10 @@ class String_expression : public Expression
   { return true; }
 
   bool
+  do_is_zero_value() const
+  { return this->val_ == ""; }
+
+  bool
   do_is_static_initializer() const
   { return true; }
 
@@ -1693,6 +1707,9 @@ class Type_conversion_expression : public Expression
   do_is_constant() const;
 
   bool
+  do_is_zero_value() const;
+
+  bool
   do_is_static_initializer() const;
 
   bool
@@ -1756,6 +1773,10 @@ class Unsafe_type_conversion_expression : public Expression
   do_traverse(Traverse* traverse);
 
   bool
+  do_is_zero_value() const
+  { return this->expr_->is_zero_value(); }
+
+  bool
   do_is_static_initializer() const;
 
   Type*
@@ -2152,6 +2173,9 @@ class String_concat_expression : public Expression
   do_is_constant() const;
 
   bool
+  do_is_zero_value() const;
+
+  bool
   do_is_static_initializer() const;
 
   Type*
@@ -3570,7 +3594,7 @@ class Struct_construction_expression : public Expression,
 	type_(type)
   { }
 
- // Return whether this is a constant initializer.
+  // Return whether this is a constant initializer.
   bool
   is_constant_struct() const;
 
@@ -3579,6 +3603,9 @@ class Struct_construction_expression : public Expression,
   do_traverse(Traverse* traverse);
 
   bool
+  do_is_zero_value() const;
+
+  bool
   do_is_static_initializer() const;
 
   Type*
@@ -3643,6 +3670,9 @@ protected:
   do_traverse(Traverse* traverse);
 
   bool
+  do_is_zero_value() const;
+
+  bool
   do_is_static_initializer() const;
 
   Type*
-- 
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