[llvm] r174345 - Add code to GlobalVariable.h so that global variables marked as

[Richard Smith]

On Mon, Feb 4, 2013 at 10:53 PM, Michael Gottesman <mgottesman at apple.com>wrote:

> Author: mgottesman
> Date: Tue Feb  5 00:53:26 2013
> New Revision: 174345
>
> URL: http://llvm.org/viewvc/llvm-project?rev=174345&view=rev
> Log:
> Add code to GlobalVariable.h so that global variables marked as
> externally_initialized return false for hasDefiniteInitializer and
> hasUniqueInitializer.
>
> rdar://12580965.
>
> Added:
>
> llvm/trunk/test/Transforms/GlobalOpt/externally-initialized-global-ctr.ll
> Modified:
>     llvm/trunk/include/llvm/IR/GlobalVariable.h
>
> Modified: llvm/trunk/include/llvm/IR/GlobalVariable.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/GlobalVariable.h?rev=174345&r1=174344&r2=174345&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/IR/GlobalVariable.h (original)
> +++ llvm/trunk/include/llvm/IR/GlobalVariable.h Tue Feb  5 00:53:26 2013
> @@ -110,7 +110,10 @@ public:
>      return hasInitializer() &&
>        // The initializer of a global variable with weak linkage may
> change at
>        // link time.
> -      !mayBeOverridden();
> +      !mayBeOverridden() &&
> +      // The initializer of a global variable with the
> externally_initialized
> +      // marker may change at runtime before cxx initializers are
> evaluated.
>

You mean "C++", not "cxx", right? (Or, more generally, before global
constructors run -- __attribute__((constructor)) functions are handled by
globalopt too.)


> +      !isExternallyInitialized();
>    }
>
>    /// hasUniqueInitializer - Whether the global variable has an
> initializer, and
> @@ -123,7 +126,11 @@ public:
>        // instead. It is wrong to modify the initializer of a global
> variable
>        // with *_odr linkage because then different instances of the
> global may
>        // have different initializers, breaking the One Definition Rule.
> -      !isWeakForLinker();
> +      !isWeakForLinker() &&
> +      // It is not safe to modify initializers of global variables with
> the
> +      // external_initializer marker since the value may be changed at
> runtime
> +      // before cxx initializers are evaluated.
> +      !isExternallyInitialized();
>    }
>
>    /// getInitializer - Return the initializer for this global variable.
>  It is
>
> Added:
> llvm/trunk/test/Transforms/GlobalOpt/externally-initialized-global-ctr.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GlobalOpt/externally-initialized-global-ctr.ll?rev=174345&view=auto
>
> ==============================================================================
> ---
> llvm/trunk/test/Transforms/GlobalOpt/externally-initialized-global-ctr.ll
> (added)
> +++
> llvm/trunk/test/Transforms/GlobalOpt/externally-initialized-global-ctr.ll
> Tue Feb  5 00:53:26 2013
> @@ -0,0 +1,35 @@
> +; RUN: opt < %s -globalopt -S | FileCheck %s
> +; rdar://12580965.
> +; ObjC++ test case.
> +
> +%struct.ButtonInitData = type { i8* }
> +
> + at _ZL14buttonInitData = internal global [1 x %struct.ButtonInitData]
> zeroinitializer, align 4
> +
> +@"\01L_OBJC_METH_VAR_NAME_40" = internal global [7 x i8] c"print:\00",
> section "__TEXT,__objc_methname,cstring_literals", align 1
> +@"\01L_OBJC_SELECTOR_REFERENCES_41" = internal externally_initialized
>  global i8* getelementptr inbounds ([7 x i8]*
> @"\01L_OBJC_METH_VAR_NAME_40", i32 0, i32 0), section "__DATA,
> __objc_selrefs, literal_pointers, no_dead_strip"
> +
> + at llvm.global_ctors = appending global [1 x { i32, void ()* }] [{ i32,
> void ()* } { i32 65535, void ()* @_GLOBAL__I_a }]
> + at llvm.used = appending global [2 x i8*] [i8* getelementptr inbounds ([7 x
> i8]* @"\01L_OBJC_METH_VAR_NAME_40", i32 0, i32 0),  i8* bitcast (i8**
> @"\01L_OBJC_SELECTOR_REFERENCES_41" to i8*)]
> +
> +define internal void @__cxx_global_var_init() section
> "__TEXT,__StaticInit,regular,pure_instructions" {
> +  %1 = load i8** @"\01L_OBJC_SELECTOR_REFERENCES_41", !invariant.load
> !2009
> +  store i8* %1, i8** getelementptr inbounds ([1 x
> %struct.ButtonInitData]* @_ZL14buttonInitData, i32 0, i32 0, i32 0), align 4
> +  ret void
> +}
> +
> +define internal void @_GLOBAL__I_a() section
> "__TEXT,__StaticInit,regular,pure_instructions" {
> +  call void @__cxx_global_var_init()
> +  ret void
> +}
> +
> +declare void @test(i8*)
> +
> +define void @print() {
> +; CHECK: %1 = load i8** getelementptr inbounds ([1 x
> %struct.ButtonInitData]* @_ZL14buttonInitData, i32 0, i32 0, i32 0), align 4
> +  %1 = load i8** getelementptr inbounds ([1 x %struct.ButtonInitData]*
> @_ZL14buttonInitData, i32 0, i32 0, i32 0), align 4
> +  call void @test(i8* %1)
> +  ret void
> +}
> +
> +!2009 = metadata !{}
> \ No newline at end of file
>
>
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