Behaviour of INLINABLE depends on whether the modules included are already compiled.

When investigating containers performance, I came across the following problem:

My Data.Map annotates nearly every method as INLINABLE. My main module Main.hs is trivial:

import Data.Map as M

main = print $ M.lookup 5 $ foldr (\x -> insert x x) empty [1..100]

Suppose my tree contains only .hs files, no .hi or .o. I can compile either by

• ghc --make -c -O Main.hs, which compiles Data/Map.hs automatically, or
• ghc --make -c -O Data/Map.hs && ghc --make -c -O Main.hs, which compiles Data/Map.hs explicitely with the same arguments first.

Expected result of both compilations: Main.o is the same.

Actual result: in the first case, Data.Map.lookup method does not get inlined in Main.o, but in the second case the Data.Map.lookup method gets inlined in Main.o.

If affects both ghc-7.0 and ghc-head branches.

I am not sure this is a bug, but I would definitely expect both of the compilation methods to yield the same file.

The self-contained source tree is attached.

Trac metadata

Trac field	Value
Version	7.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
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CC	simonpj
Operating system
Architecture