> It'd be better to make the both zero-sized, like an array of i8 with
zero elements. This idiom has come up before, and that's our recommended
solution. We've tweaked the optimizers to ensure that zero-sized objects are
not assumed to be distinct.
Okay, I have rewritten my clear BSS section function as :
;————
@__bss_start = external global [0 x i32]
@__bss_end = external global [0 x i32]
define void @clearBSS () nounwind {
entry:
%startPtr = getelementptr [0 x i32], [0 x i32]* @__bss_start, i32 0, i32 0
%endPtr = getelementptr [0 x i32], [0 x i32]* @__bss_end, i32 0, i32 0
br label %bssLoopTest
bssLoopTest:
%p = phi i32* [%startPtr, %entry], [%p.next, %bssLoop]
%completed = icmp eq i32* %p, %endPtr
br i1 %completed, label %clearCompleted, label %bssLoop
bssLoop:
store i32 0, i32* %p, align 4
%p.next = getelementptr inbounds i32, i32* %p, i32 1
br label %bssLoopTest
clearCompleted:
ret void
}
;————
It works, opt preserves the while loop.
Thanks,
Pierre Molinaro
> Le 28 août 2015 à 17:59, Reid Kleckner via llvm-dev <llvm-dev at
lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> a écrit :
>
> On Fri, Aug 28, 2015 at 8:27 AM, Joerg Sonnenberger via llvm-dev
<llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>>
wrote:
> On Fri, Aug 28, 2015 at 04:52:56PM +0200, devh8h via llvm-dev wrote:
> > Is there a way to prevent the optimizer to assume the two variables
> > are distinct ? Or what is the proper way to deal with link time values
?
>
> Make one of them weak.
>
> It'd be better to make the both zero-sized, like an array of i8 with
zero elements. This idiom has come up before, and that's our recommended
solution. We've tweaked the optimizers to ensure that zero-sized objects are
not assumed to be distinct.
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