diff options
| -rw-r--r-- | compiler/cmm/CmmSink.hs | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/compiler/cmm/CmmSink.hs b/compiler/cmm/CmmSink.hs index 7acc4dd460..2ff9b98d2a 100644 --- a/compiler/cmm/CmmSink.hs +++ b/compiler/cmm/CmmSink.hs @@ -465,6 +465,27 @@ data AbsMem -- Note that SpMem is invalidated if Sp is changed, but the definition -- of 'conflicts' above handles that. +-- ToDo: this won't currently fix the following commonly occurring code: +-- x1 = [R1 + 8] +-- x2 = [R1 + 16] +-- .. +-- [Hp - 8] = x1 +-- [Hp - 16] = x2 +-- .. + +-- because [R1 + 8] and [Hp - 8] are both HeapMem. We know that +-- assignments to [Hp + n] do not conflict with any other heap memory, +-- but this is tricky to nail down. What if we had +-- +-- x = Hp + n +-- [x] = ... +-- +-- the store to [x] should be "new heap", not "old heap". +-- Furthermore, you could imagine that if we started inlining +-- functions in Cmm then there might well be reads of heap memory +-- that was written in the same basic block. To take advantage of +-- non-aliasing of heap memory we will have to be more clever. + bothMems :: AbsMem -> AbsMem -> AbsMem bothMems NoMem x = x bothMems x NoMem = x |