[gem5-dev] [S] Change in gem5/gem5[develop]: mem-ruby: Optimize enum to string conversion in SLICC

[Gabriel B. (Gerrit) via gem5-dev]

Gabriel B. has uploaded this change for review. (  
https://gem5-review.googlesource.com/c/public/gem5/+/67676?usp=email )

Change subject: mem-ruby: Optimize enum to string conversion in SLICC
......................................................................

mem-ruby: Optimize enum to string conversion in SLICC

The result was previously returned in a brand new std::string every
time. std::strings are now cached in a static const array and returned
by const reference.

Change-Id: I5ef6e3ef94898bc606e29b950caef9ab32935da2
---
M src/mem/slicc/ast/EnumDeclAST.py
M src/mem/slicc/ast/StateDeclAST.py
M src/mem/slicc/symbols/Type.py
3 files changed, 24 insertions(+), 16 deletions(-)



diff --git a/src/mem/slicc/ast/EnumDeclAST.py  
b/src/mem/slicc/ast/EnumDeclAST.py
index 5ffc8bb..25fd124 100644
--- a/src/mem/slicc/ast/EnumDeclAST.py
+++ b/src/mem/slicc/ast/EnumDeclAST.py
@@ -66,7 +66,7 @@
         # Add the implicit State_to_string method - FIXME, this is a bit  
dirty
         func_id = "%s_to_string" % t.c_ident

-        pairs = {"external": "yes"}
+        pairs = {"external": "yes", "return_by_const_ref": "yes"}
         func = Func(
             self.symtab,
             func_id + "_" + t.c_ident,
diff --git a/src/mem/slicc/ast/StateDeclAST.py  
b/src/mem/slicc/ast/StateDeclAST.py
index f6e5d6e..ae50b82 100644
--- a/src/mem/slicc/ast/StateDeclAST.py
+++ b/src/mem/slicc/ast/StateDeclAST.py
@@ -65,7 +65,7 @@
         # Add the implicit State_to_string method - FIXME, this is a bit  
dirty
         func_id = "%s_to_string" % t.c_ident

-        pairs = {"external": "yes"}
+        pairs = {"external": "yes", "return_by_const_ref": "yes"}
         func = Func(
             self.symtab,
             func_id + "_" + t.ident,
diff --git a/src/mem/slicc/symbols/Type.py b/src/mem/slicc/symbols/Type.py
index a0bcd7b..797ced5 100644
--- a/src/mem/slicc/symbols/Type.py
+++ b/src/mem/slicc/symbols/Type.py
@@ -582,7 +582,7 @@
 ${{self.c_ident}} string_to_${{self.c_ident}}(const ::std::string& str);

 // Code to convert state to a string
-::std::string ${{self.c_ident}}_to_string(const ${{self.c_ident}}& obj);
+const ::std::string& ${{self.c_ident}}_to_string(const ${{self.c_ident}}&  
obj);

 // Code to increment an enumeration type
 ${{self.c_ident}} &operator++(${{self.c_ident}} &e);
@@ -735,29 +735,24 @@
 }

 // Code to convert state to a string
-std::string
+const std::string&
 ${{self.c_ident}}_to_string(const ${{self.c_ident}}& obj)
 {
-    switch(obj) {
+    static const std::array<std::string, ${{self.c_ident}}_NUM> lut = {
 """
         )
-
-        # For each field
+        code.indent()
         code.indent()
         for enum in self.enums.values():
-            code("  case ${{self.c_ident}}_${{enum.ident}}:")
-            code('    return "${{enum.ident}}";')
+            code('"${{enum.ident}}",')
         code.dedent()
+        code("};")
+        code("return lut.at(obj);")
+        code.dedent()
+        code("}")

-        # Trailer
         code(
             """
-      default:
-        panic("Invalid range for type ${{self.c_ident}}");
-    }
-    // Appease the compiler since this function has a return value
-    return "";
-}

 // Code to convert from a string to the enumeration
 ${{self.c_ident}}

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Gerrit-Project: public/gem5
Gerrit-Branch: develop
Gerrit-Change-Id: I5ef6e3ef94898bc606e29b950caef9ab32935da2
Gerrit-Change-Number: 67676
Gerrit-PatchSet: 1
Gerrit-Owner: Gabriel B. <gabriel.bus...@arteris.com>
Gerrit-MessageType: newchange
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