[PATCH] CloneFunctionInto incorrectly cloning attributes

[Joey Gouly]

Hi all,

Attached is a patch to fix a bug in llvm::CloneFunctionInto.

Firstly, the amount of arguments are compared, and if they are equal the
attributes are copied over directly.
This is wrong if you are cloning into a function with the same number of
arguments, but if they are not actually
the same arguments.

After the first change, the attributes were still being cloned incorrectly.
So the second change is using
get(Ret/Fn)Attributes() instead of getAttributes(). This may not be the
right way to fix this, I'm hoping
Brian Wendling can say if this is a bug here, or in the Attributes API.

Example of how these bugs happen:

define void @x(i32* nocapture %a, i32 %b) {
  ret void
}

declare void @y(i64 %a, i64 %b)

Without my changes, after CloneFunctionInto(@y, @x):

define void @x(i32* nocapture %a, i32 %b) {
  ret void
}

define void @y(i64 nocapture %c, i64 %d) {
  ret void
}

Which is wrong, as it has put the nocapture attribute on %c, because they
have the same number of arguments.

Any comments? Good to commit?

Thanks,
Joey
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