http://llvm.org/bugs/show_bug.cgi?id=15402
Bug ID: 15402
Summary: GlobalOpt creates giant initializers leading to
excessively large object files
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Interprocedural Optimizations
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
Created attachment 10112
--> http://llvm.org/bugs/attachment.cgi?id=10112&action=edit
Reduced .ll file
This appears to be an optimization bug to me where GlobalOpt sacrifices file
size at any cost.
In the example I have a large array which was originally marked as
zeroinitializer, and store to the array in the c-tor chain. When GlobalOpt
runs it builds a very large initializer of all zeros except for the one
non-zero value written in the c-tor chain. Which results in a very large
object file just to initialize one element of this array. To reproduce run
globalopt on the attached file.
For reference here is the original c++
int __attribute__((used)) bob[1000000];
int foo() {
bob[10] = 99;
return 0;
}
int x = foo();
int main() {
return 0;
}
I was hoping to get some general advise as to the best way to do sparse data
initialization efficiently. It seems the ELF itself sort of limits this due to
the contiguous nature of its sections, so any ideas would be appreciated.
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