1. Check for revisiting a block before checking domination, which is faster.
2. If the stored value isn't an instruction, we don't have to check for domination.
3. If we have a value used in the same block more than once, make sure to remove the
block from the UsingBlocks vector. Not doing so forces us to go through the slow
path for the alloca.
The combination of these improvements increases the number of allocas on the fastpath
from 8935 to 8982 on PR1432. This speeds it up from 2.90s to 2.20s (31%)
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a using block from the list if we handle it. Not doing this caused us
to not be able to promote (with the fast path) allocas which have uses (whoops).
This increases the # allocas hitting this fastpath from 4042 to 8935 on the
testcase in PR1432, speeding up mem2reg by 2.6x
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BBNumbers. Instead of using a bi-directional mapping, just use a single
densemap. This speeds up mem2reg on 176.gcc by 8%, from 1.3489 to
1.2485s.
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nondeterminism being bad) could cause some trivial missed optimizations (dead
phi nodes being left around for later passes to clean up).
With this, llvm-gcc4 now bootstraps and correctly compares. I don't know
why I never tried to do it before... :)
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has a single def. In this case, look for uses that are dominated by the def
and attempt to rewrite them to directly use the stored value.
This speeds up mem2reg on these values and reduces the number of phi nodes
inserted. This should address PR665.
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BasicBlock's removePredecessor routine. This requires shuffling around
the definition and implementation of hasContantValue from Utils.h,cpp into
Instructions.h,cpp
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The optimization for locally used allocas was not safe for allocas that
were read before they were written. This change disables that optimization
in that case.
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particular, invoke ret values are only live in the normal dest of the invoke
not in the unwind dest.
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unneccesary. This allows us to delete several hundred phi nodes of the
form PHI(x,x,x,undef) from 253.perlbmk and probably other programs as well.
This implements Mem2Reg/UndefValuesMerge.ll
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whose addresses where used by trivial phi nodes and select instructions. This
is now performed by the instcombine pass, which is more powerful, is much
simpler, and is faster. This allows the deletion of a bunch of code, two
FIXME's and two gotos.
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Move include/Config and include/Support into include/llvm/Config,
include/llvm/ADT and include/llvm/Support. From here on out, all LLVM
public header files must be under include/llvm/.
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non-deterministic things like the ordering of blocks in the dominance
frontier of a BB. Unfortunately, I don't know of a better way to solve
this problem than to explicitly sort the BB's in function-order before
processing them. This is guaranteed to slow the pass down a bit, but
is absolutely necessary to get usable diffs between two different tools
executing the mem2reg or scalarrepl pass.
Before this, bazillions of spurious diff failures occurred all over the
place due to the different order of processing PHIs:
- %tmp.111 = getelementptr %struct.Connector_struct* %upcon.0.0, uint 0, uint 0
+ %tmp.111 = getelementptr %struct.Connector_struct* %upcon.0.1, uint 0, uint 0
Now, the diffs match.
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process them all as a group. This speeds up SRoA/mem2reg from 28.46s to
0.62s on the testcase from PR209.
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