(x & 2^n) ? 2^m+C : C
we can offset both arms by C to get the "(x & 2^n) ? 2^m : 0" form, optimize the
select to a shift and apply the offset afterwards.
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The last uses of these functions were removed in r113852 when LazyValueInfo was permanently enabled and removed the need for them.
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zextOrTrunc(), and APSInt methods extend(), extOrTrunc() and new method
trunc(), to be const and to return a new value instead of modifying the
object in place.
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(if available) as we go so that we get simple constantexprs not insane ones.
This fixes the failure of clang/test/CodeGenCXX/virtual-base-ctor.cpp
that the previous iteration of this patch had.
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optimization.
Consider:
static void foo() {
A = alloca
...
}
static void bar() {
B = alloca
...
call foo();
}
void main() {
bar()
}
The inliner proceeds bottom up, but lets pretend it decides not to inline foo
into bar. When it gets to main, it inlines bar into main(), and says "hey, I
just inlined an alloca "B" into main, lets remember that. Then it keeps going
and finds that it now contains a call to foo. It decides to inline foo into
main, and says "hey, foo has an alloca A, and I have an alloca B from another
inlined call site, lets reuse it". The problem with this of course, is that
the lifetime of A and B are nested, not disjoint.
Unfortunately I can't create a reasonable testcase for this: the one in the
PR is both huge and extremely sensitive, because you minor tweaks end up
causing foo to get inlined into bar too early. We already have tests for the
basic alloca merging optimization and this does not break them.
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memcpy's like:
memcpy(A, B)
memcpy(A, C)
we cannot delete the first memcpy as dead if A and C might be aliases.
If so, we actually get:
memcpy(A, B)
memcpy(A, A)
which is not correct to transform into:
memcpy(A, A)
This patch was heavily influenced by Jakub Staszak's patch in PR8728, thanks
Jakub!
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Should have no functional change other than the order of two transformations that are mutually-exclusive and the exact formatting of debug output.
Internally, it now stores the ConstantInt*s as Constant*s, and actual undef values instead of nulls.
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20040709-1.c from the gcc testsuite. I was using the size of a
pointer instead of the pointee. This fixes rdar://8713376
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may-aliasing stores that partially overlap with different base
pointers. This implements PR6043 and the non-variable part of
PR8657
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1. if the underlying pointer passed in can be resolved
to any argument or alloca, then we don't need to scan.
Previously we would only avoid the scan if the alloca
or byval was actually considered dead.
2. The dead store processing code is itself completely
dead and didn't handle volatile stores right anyway,
so delete it. This allows simplifying the interface
to RemoveAccessedObjects.
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made sense to me. We now have a set of dead stack objects, and
they become live when loaded. Fix a theoretical problem where
we'd pass in the wrong pointer to the alias query.
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If the call might read all the allocas, stop scanning early.
Convert a vector to smallvector, shrink SmallPtrSet to 16 instead
of 64 to avoid crazy linear scans.
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now that DSE hacks on them. This fixes a regression I introduced,
by generalizing DSE to hack on transfers.
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about pairs of AA::Location's instead of looking for MemDep's
"Def" predicate. This is more powerful and general, handling
memset/memcpy/store all uniformly, and implementing PR8701 and
probably obsoleting parts of memcpyoptimizer.
This also fixes an obscure bug with init.trampoline and i8
stores, but I'm not surprised it hasn't been hit yet. Enhancing
init.trampoline to carry the size that it stores would allow
DSE to be much more aggressive about optimizing them.
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is trivially dead, since these have side effects. This makes the
(misnamed) MemoryUseIntrinsic class dead, so remove it.
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contains "ref".
Enhance DSE to use a modref query instead of a store-specific hack
to generalize the "ignore may-alias stores" optimization to handle
memset and memcpy.
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1. Don't bother trying to optimize:
lifetime.end(ptr)
store(ptr)
as it is undefined, and therefore shouldn't exist.
2. Move the 'storing a loaded pointer' xform up, simplifying
the may-aliased store code.
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