[PATCH] D59873: Add additional mangling for struct members of non trivial structs

[Dan Zimmerman via Phabricator via cfe-commits]

danzimm created this revision.
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In https://bugs.llvm.org/show_bug.cgi?id=41206 we observe bad codegen when 
embedding a non-trivial C struct within a C struct. This is due to the fact 
that name mangling for non-trivial structs marks the two structs as identical. 
This diff contains a potential fix for this issue. I've included a test that 
exercises this for two scenarios. Please comment if there're any other 
scenarios I should consider.

Test Plan: I've included a unit test


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D59873

Files:
  clang/lib/CodeGen/CGNonTrivialStruct.cpp


Index: clang/lib/CodeGen/CGNonTrivialStruct.cpp
===================================================================
--- clang/lib/CodeGen/CGNonTrivialStruct.cpp
+++ clang/lib/CodeGen/CGNonTrivialStruct.cpp
@@ -139,8 +139,8 @@
 // <alignment-info> ::= <dst-alignment> ["_" <src-alignment>]
 // <struct-field-info> ::= <field-info>+
 // <field-info> ::= <struct-or-scalar-field-info> | <array-field-info>
-// <struct-or-scalar-field-info> ::= <struct-field-info> | <strong-field-info> 
|
-//                                   <trivial-field-info>
+// <struct-or-scalar-field-info> ::= "_S" <struct-field-info> |
+//                                   <strong-field-info> | <trivial-field-info>
 // <array-field-info> ::= "_AB" <array-offset> "s" <element-size> "n"
 //                        <num-elements> <innermost-element-info> "_AE"
 // <innermost-element-info> ::= <struct-or-scalar-field-info>
@@ -175,6 +175,7 @@
   void visitStruct(QualType QT, const FieldDecl *FD,
                    CharUnits CurStructOffset) {
     CharUnits FieldOffset = CurStructOffset + asDerived().getFieldOffset(FD);
+    appendStr("_S");
     asDerived().visitStructFields(QT, FieldOffset);
   }
 



Index: clang/lib/CodeGen/CGNonTrivialStruct.cpp
===================================================================
--- clang/lib/CodeGen/CGNonTrivialStruct.cpp
+++ clang/lib/CodeGen/CGNonTrivialStruct.cpp
@@ -139,8 +139,8 @@
 // <alignment-info> ::= <dst-alignment> ["_" <src-alignment>]
 // <struct-field-info> ::= <field-info>+
 // <field-info> ::= <struct-or-scalar-field-info> | <array-field-info>
-// <struct-or-scalar-field-info> ::= <struct-field-info> | <strong-field-info> |
-//                                   <trivial-field-info>
+// <struct-or-scalar-field-info> ::= "_S" <struct-field-info> |
+//                                   <strong-field-info> | <trivial-field-info>
 // <array-field-info> ::= "_AB" <array-offset> "s" <element-size> "n"
 //                        <num-elements> <innermost-element-info> "_AE"
 // <innermost-element-info> ::= <struct-or-scalar-field-info>
@@ -175,6 +175,7 @@
   void visitStruct(QualType QT, const FieldDecl *FD,
                    CharUnits CurStructOffset) {
     CharUnits FieldOffset = CurStructOffset + asDerived().getFieldOffset(FD);
+    appendStr("_S");
     asDerived().visitStructFields(QT, FieldOffset);
   }
 

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