http://llvm.org/bugs/show_bug.cgi?id=8993
Summary: Constant string codegen broken by r123585
Product: libraries
Version: trunk
Platform: PC
OS/Version: All
Status: NEW
Severity: normal
Priority: P
Component: Common Code Generator Code
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Created an attachment (id=6016)
--> (http://llvm.org/bugs/attachment.cgi?id=6016)
simple sample file
“123585 by rafael, 18:19
Only put unnamed_addr constants in mergeable sections. Fixes PR8297.
Modified /llvm/trunk/lib/Target/TargetLoweringObjectFile.cpp”
After this commit, most C string end up in the data segment instead of text
segment, just like if the compiler was invoked with -fwritable-string.
This is a important issue as it break CFString and constant obj-c string
codegen with clang.
When trying to link any object compiled after this change, the linker emit this
warning for each object that contains constant CF/NSString.
ld: warning: -fwritable-strings not compatible with literal CF/NSString in
/WBAEFunctions.o
And here is a sample of the assembly generated before and after this change:
----------- before:
.section __TEXT,__cstring,cstring_literals
L_.str: ## @.str
.asciz "Hello World"
----------- after:
.section __DATA,__data
L_.str: ## @.str
.asciz "Hello World"
I attached a sample file used to generate this assembly and the result before
and after the change.
I simply use "clang -S" to compile this file.
Note: the default target is x86_64-apple-darwin10
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