r199709 - Use private linkage for utf-16 objc strings too.

Bob Wilson bob.wilson at apple.com
Tue Feb 25 16:30:47 PST 2014 

Rafael, this change is causing problems. Apple’s linker needs to see labels in the __ustring sections, and with this change, the ustring labels are local to the assembler and never seen at link-time. Please revert this. We can investigate getting the linker to relax that constraint in the future, but it doesn’t work now.

On Jan 20, 2014, at 6:57 PM, Rafael Espindola <rafael.espindola at gmail.com> wrote:

> Author: rafael
> Date: Mon Jan 20 20:57:56 2014
> New Revision: 199709
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=199709&view=rev
> Log:
> Use private linkage for utf-16 objc strings too.
> 
> Modified:
>    cfe/trunk/lib/CodeGen/CodeGenModule.cpp
>    cfe/trunk/test/CodeGen/darwin-string-literals.c
>    cfe/trunk/test/CodeGen/utf16-cfstrings.c
>    cfe/trunk/test/CodeGenObjC/2009-08-05-utf16.m
>    cfe/trunk/test/CodeGenObjC/2010-02-01-utf16-with-null.m
> 
> Modified: cfe/trunk/lib/CodeGen/CodeGenModule.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenModule.cpp?rev=199709&r1=199708&r2=199709&view=diff
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CodeGenModule.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CodeGenModule.cpp Mon Jan 20 20:57:56 2014
> @@ -2378,18 +2378,11 @@ CodeGenModule::GetAddrOfConstantCFString
>     C = llvm::ConstantDataArray::getString(VMContext, Entry.getKey());
>   }
> 
> -  llvm::GlobalValue::LinkageTypes Linkage;
> -  if (isUTF16)
> -    // FIXME: why do utf strings get "_" labels instead of "L" labels?
> -    Linkage = llvm::GlobalValue::InternalLinkage;
> -  else
> -    Linkage = llvm::GlobalValue::PrivateLinkage;
> -
>   // Note: -fwritable-strings doesn't make the backing store strings of
>   // CFStrings writable. (See <rdar://problem/10657500>)
>   llvm::GlobalVariable *GV =
> -    new llvm::GlobalVariable(getModule(), C->getType(), /*isConstant=*/true,
> -                             Linkage, C, ".str");
> +      new llvm::GlobalVariable(getModule(), C->getType(), /*isConstant=*/true,
> +                               llvm::GlobalValue::PrivateLinkage, C, ".str");
>   GV->setUnnamedAddr(true);
>   // Don't enforce the target's minimum global alignment, since the only use
>   // of the string is via this class initializer.
> 
> Modified: cfe/trunk/test/CodeGen/darwin-string-literals.c
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/darwin-string-literals.c?rev=199709&r1=199708&r2=199709&view=diff
> ==============================================================================
> --- cfe/trunk/test/CodeGen/darwin-string-literals.c (original)
> +++ cfe/trunk/test/CodeGen/darwin-string-literals.c Mon Jan 20 20:57:56 2014
> @@ -2,16 +2,16 @@
> 
> // CHECK-LSB: @.str = private unnamed_addr constant [8 x i8] c"string0\00"
> // CHECK-LSB: @.str1 = private unnamed_addr constant [8 x i8] c"string1\00"
> -// CHECK-LSB: @.str2 = internal unnamed_addr constant [18 x i16] [i16 104, i16 101, i16 108, i16 108, i16 111, i16 32, i16 8594, i16 32, i16 9731, i16 32, i16 8592, i16 32, i16 119, i16 111, i16 114, i16 108, i16 100, i16 0], section "__TEXT,__ustring", align 2
> -// CHECK-LSB: @.str4 = internal unnamed_addr constant [6 x i16] [i16 116, i16 101, i16 115, i16 116, i16 8482, i16 0], section "__TEXT,__ustring", align 2
> +// CHECK-LSB: @.str2 = private unnamed_addr constant [18 x i16] [i16 104, i16 101, i16 108, i16 108, i16 111, i16 32, i16 8594, i16 32, i16 9731, i16 32, i16 8592, i16 32, i16 119, i16 111, i16 114, i16 108, i16 100, i16 0], section "__TEXT,__ustring", align 2
> +// CHECK-LSB: @.str4 = private unnamed_addr constant [6 x i16] [i16 116, i16 101, i16 115, i16 116, i16 8482, i16 0], section "__TEXT,__ustring", align 2
> 
> 
> // RUN: %clang_cc1 -triple powerpc-apple-darwin9 -emit-llvm %s -o - | FileCheck -check-prefix CHECK-MSB %s
> 
> // CHECK-MSB: @.str = private unnamed_addr constant [8 x i8] c"string0\00"
> // CHECK-MSB: @.str1 = private unnamed_addr constant [8 x i8] c"string1\00"
> -// CHECK-MSB: @.str2 = internal unnamed_addr constant [18 x i16] [i16 104, i16 101, i16 108, i16 108, i16 111, i16 32, i16 8594, i16 32, i16 9731, i16 32, i16 8592, i16 32, i16 119, i16 111, i16 114, i16 108, i16 100, i16 0], section "__TEXT,__ustring", align 2
> -// CHECK-MSB: @.str4 = internal unnamed_addr constant [6 x i16] [i16 116, i16 101, i16 115, i16 116, i16 8482, i16 0], section "__TEXT,__ustring", align 2
> +// CHECK-MSB: @.str2 = private unnamed_addr constant [18 x i16] [i16 104, i16 101, i16 108, i16 108, i16 111, i16 32, i16 8594, i16 32, i16 9731, i16 32, i16 8592, i16 32, i16 119, i16 111, i16 114, i16 108, i16 100, i16 0], section "__TEXT,__ustring", align 2
> +// CHECK-MSB: @.str4 = private unnamed_addr constant [6 x i16] [i16 116, i16 101, i16 115, i16 116, i16 8482, i16 0], section "__TEXT,__ustring", align 2
> 
> const char *g0 = "string0";
> const void *g1 = __builtin___CFStringMakeConstantString("string1");
> 
> Modified: cfe/trunk/test/CodeGen/utf16-cfstrings.c
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/utf16-cfstrings.c?rev=199709&r1=199708&r2=199709&view=diff
> ==============================================================================
> --- cfe/trunk/test/CodeGen/utf16-cfstrings.c (original)
> +++ cfe/trunk/test/CodeGen/utf16-cfstrings.c Mon Jan 20 20:57:56 2014
> @@ -1,7 +1,7 @@
> // RUN: %clang_cc1 -triple x86_64-apple-darwin -emit-llvm %s -o - | FileCheck %s
> // <rdar://problem/10655949>
> 
> -// CHECK: @.str = internal unnamed_addr constant [9 x i16] [i16 252, i16 98, i16 101, i16 114, i16 104, i16 117, i16 110, i16 100, i16 0], section "__TEXT,__ustring", align 2
> +// CHECK: @.str = private unnamed_addr constant [9 x i16] [i16 252, i16 98, i16 101, i16 114, i16 104, i16 117, i16 110, i16 100, i16 0], section "__TEXT,__ustring", align 2
> 
> #define CFSTR __builtin___CFStringMakeConstantString
> 
> 
> Modified: cfe/trunk/test/CodeGenObjC/2009-08-05-utf16.m
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenObjC/2009-08-05-utf16.m?rev=199709&r1=199708&r2=199709&view=diff
> ==============================================================================
> --- cfe/trunk/test/CodeGenObjC/2009-08-05-utf16.m (original)
> +++ cfe/trunk/test/CodeGenObjC/2009-08-05-utf16.m Mon Jan 20 20:57:56 2014
> @@ -1,5 +1,5 @@
> // RUN: %clang_cc1 -emit-llvm -w -x objective-c %s -o - | FileCheck %s
> // rdar://7095855 rdar://7115749
> 
> -// CHECK: internal unnamed_addr constant [6 x i16] [i16 105, i16 80, i16 111, i16 100, i16 8482, i16 0], section "__TEXT,__ustring", align 2
> +// CHECK: private unnamed_addr constant [6 x i16] [i16 105, i16 80, i16 111, i16 100, i16 8482, i16 0], section "__TEXT,__ustring", align 2
> void *P = @"iPod™";
> 
> Modified: cfe/trunk/test/CodeGenObjC/2010-02-01-utf16-with-null.m
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenObjC/2010-02-01-utf16-with-null.m?rev=199709&r1=199708&r2=199709&view=diff
> ==============================================================================
> --- cfe/trunk/test/CodeGenObjC/2010-02-01-utf16-with-null.m (original)
> +++ cfe/trunk/test/CodeGenObjC/2010-02-01-utf16-with-null.m Mon Jan 20 20:57:56 2014
> @@ -1,7 +1,7 @@
> // RUN: %clang_cc1 -triple i686-apple-darwin -emit-llvm %s -o - | FileCheck %s
> // rdar://7589850
> 
> -// CHECK: @.str = internal unnamed_addr constant [9 x i16] [i16 103, i16 111, i16 111, i16 100, i16 0, i16 98, i16 121, i16 101, i16 0], section "__TEXT,__ustring", align 2
> +// CHECK: @.str = private unnamed_addr constant [9 x i16] [i16 103, i16 111, i16 111, i16 100, i16 0, i16 98, i16 121, i16 101, i16 0], section "__TEXT,__ustring", align 2
> // CHECK: @_unnamed_cfstring_ = private constant %struct.NSConstantString { i32* getelementptr inbounds ([0 x i32]* @__CFConstantStringClassReference, i32 0, i32 0), i32 2000, i8* bitcast ([9 x i16]* @.str to i8*), i32 8 }, section "__DATA,__cfstring"
> // CHECK: @P = global i8* bitcast (%struct.NSConstantString* @_unnamed_cfstring_ to i8*), align 4
> void *P = @"good\0bye";
> 
> 
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