Commit bec3c049 authored by Jan Stolarek's avatar Jan Stolarek

Drop proc-points that don't exist in the graph (#8205)

On some architectures it might happen that stack layout pass will
invalidate the list of calculated procpoints by dropping some of
them. We fix this by checking whether a proc-point is in a graph
at the beginning of proc-point analysis. This is a speculative
fix for #8205.
parent 43111a0b
......@@ -83,6 +83,33 @@ most once per iteration, then recompute the reachability information.
arbitrary, and I don't know if the choice affects the final solution,
so I don't know if the number of proc points chosen is the
minimum---but the set will be minimal.
Note [Proc-point analysis]
~~~~~~~~~~~~~~~~~~~~~~~~~~
Given a specified set of proc-points (a set of block-ids), "proc-point
analysis" figures out, for every block, which proc-point it belongs to.
All the blocks belonging to proc-point P will constitute a single
top-level C procedure.
A non-proc-point block B "belongs to" a proc-point P iff B is
reachable from P without going through another proc-point.
Invariant: a block B should belong to at most one proc-point; if it
belongs to two, that's a bug.
Note [Non-existing proc-points]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
On some architectures it might happen that the list of proc-points
computed before stack layout pass will be invalidated by the stack
layout. This will happen if stack layout removes from the graph
blocks that were determined to be proc-points. Later on in the pipeline
we use list of proc-points to perform [Proc-point analysis], but
if a proc-point does not exist anymore then we will get compiler panic.
See #8205.
-}
type ProcPointSet = BlockSet
......@@ -104,11 +131,14 @@ instance Outputable Status where
procPointAnalysis :: ProcPointSet -> CmmGraph -> UniqSM (BlockEnv Status)
-- Once you know what the proc-points are, figure out
-- what proc-points each block is reachable from
procPointAnalysis procPoints g =
-- See Note [Proc-point analysis]
procPointAnalysis procPoints g@(CmmGraph {g_graph = graph}) =
-- pprTrace "procPointAnalysis" (ppr procPoints) $
dataflowAnalFwdBlocks g initProcPoints $ analFwd lattice forward
where initProcPoints = [(id, ProcPoint) | id <- setElems procPoints]
where initProcPoints = [(id, ProcPoint) | id <- setElems procPoints,
id `setMember` labelsInGraph ]
-- See Note [Non-existing proc-points]
labelsInGraph = labelsDefined graph
-- transfer equations
forward :: FwdTransfer CmmNode Status
......
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