Interprocedural constant propagation ignores weak attribute

[llvmbot]

Bugzilla Link	2411
Resolution	FIXED
Resolved on	Sep 01, 2008 10:21
Version	unspecified
OS	Linux
Depends On	llvm/llvm-bugzilla-archive#2742
Attachments	Test case, Result of -ipconstprop
Reporter	LLVM Bugzilla Contributor

Extended Description

Interprocedural constant propagation (-ipconstprop) propagates the result of foo to main, regardless the weak attribute of foo:

define weak i32 @​foo() nounwind {
entry:
ret i32 1
}

define i32 @​main() nounwind {
entry:
%tmp1 = call i32 @​foo( ) nounwind
ret i32 %tmp1
}

test.ll as attached is the test case and test-ipconstprop.ll is the result after applying "opt -ipconstprop".

[llvmbot]

Several problems with weak functions are known, but I wasn't aware of
this one. Thanks for pointing it out! There is currently some discussion
of the best way of handling this kind of thing: audit all optimizers,
or set things up differently so that it is impossible to make mistakes
of this kind.

[lattner]

Fixed:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20080609/063502.html

Nice testcase!

[llvmbot]

mentioned in issue llvm/llvm-bugzilla-archive#2742