method that returns its result as a DepResultTy instead of as a
MemDepResult. This reduces conversion back and forth.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60266 91177308-0d34-0410-b5e6-96231b3b80d8
dependencies. The basic situation was this: consider if we had:
store1
...
store2
...
store3
Where memdep thinks that store3 depends on store2 and store2 depends
on store1. The problem happens when we delete store2: The code in
question was updating dep info for store3 to be store1. This is a
spiffy optimization, but is not safe at all, because aliasing isn't
transitive. This bug isn't exposed today with DSE because DSE will only
zap store2 if it is identifical to store 3, and in this case, it is
safe to update it to depend on store1. However, memcpyopt is not so
fortunate, which is presumably why the "dropInstruction" code used to
exist.
Since this doesn't actually provide a speedup in practice, just rip the
code out.
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an entry in the nonlocal deps map, don't reset entries
referencing that instruction to [dirty, null], instead, set
them to [dirty,next] where next is the instruction after the
deleted one. Use this information in the non-local deps
code to avoid rescanning entire blocks.
This speeds up GVN slightly by avoiding pointless work. On
403.gcc this makes GVN 1.5% faster.
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Put a some code back to handle buggy behavior that GVN expects: it wants
loads to depend on each other, and accesses to depend on their allocations.
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former does caching, the later doesn't. This dramatically simplifies
the logic in getDependency and getDependencyFrom.
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Document the Dirty value more precisely, use it for the uninitialized
DepResultTy value. Change reverse mappings to be from an instruction*
instead of DepResultTy, and stop tracking other forms. This makes it more
clear that we only care about the instruction cases.
Eliminate a DepResultTy,bool pair by using Dirty in the local case as well,
shrinking the map and simplifying the code.
This speeds up GVN by ~3% on 403.gcc.
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query. This makes it crystal clear what cases can escape from MemDep that
the clients have to handle. This also gives the clients a nice simplified
interface to it that is easy to poke at.
This patch also makes DepResultTy and MemoryDependenceAnalysis::DepType
private, yay.
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of a pointer/int pair instead of a manually bitmangled pointer.
This forces clients to think a little more about checking the
appropriate pieces and will be useful for internal
implementation improvements later.
I'm not particularly happy with this. After going through this
I don't think that the clients of memdep should be exposed to
the internal type at all. I'll fix this in a subsequent commit.
This has no functionality change.
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properly updates the reverse dependency map when it installs updated
dependencies for instructions that depend on the removed instruction.
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but it doesn't make any sense at all.
Also make the method const, private, and fit in 80 cols while we're at it.
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nothing to do with dead instruction elimination. No tests in
dejagnu depend on this, so I don't know what it was needed for.
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