(performing the addition in a wider type and explicitly checking for overflow), and
fold them down to intrinsics. This currently only supports signed-addition, but could
be generalized if someone works out the magic constant formulas for other operations.
Fixes <rdar://problem/8558713>.
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When it sees a promising select it now tries to figure out whether the condition of the select is known in any of the predecessors and if so it maps the operands appropriately.
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which is simpler than finding a place to insert in BB.
- Don't perform the 'if condition hoisting' xform on certain
i1 PHIs, as it interferes with switch formation.
This re-fixes "example 7", without breaking the world hopefully.
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first, it can kick in on blocks whose conditions have been
folded to a constant, even though one of the edges will be
trivially folded.
second, it doesn't clean up the "if diamond" that it just
eliminated away. This is a problem because other simplifycfg
xforms kick in depending on the order of block visitation,
causing pointless work.
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when simplifying, allowing them to be eagerly turned into switches. This
is the last step required to get "Example 7" from this blog post:
http://blog.regehr.org/archives/320
On X86, we now generate this machine code, which (to my eye) seems better
than the ICC generated code:
_crud: ## @crud
## BB#0: ## %entry
cmpb $33, %dil
jb LBB0_4
## BB#1: ## %switch.early.test
addb $-34, %dil
cmpb $58, %dil
ja LBB0_3
## BB#2: ## %switch.early.test
movzbl %dil, %eax
movabsq $288230376537592865, %rcx ## imm = 0x400000017001421
btq %rax, %rcx
jb LBB0_4
LBB0_3: ## %lor.rhs
xorl %eax, %eax
ret
LBB0_4: ## %lor.end
movl $1, %eax
ret
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(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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(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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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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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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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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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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