down approach, inspired by discussions with Tanya.
This approach is significantly faster, because it does not need dominator
frontiers and it does not insert extraneous unused PHI nodes. For example, on
252.eon, in a release-asserts build, this speeds up LCSSA (which is the slowest
pass in gccas) from 9.14s to 0.74s on my G5. This code is also slightly smaller
and significantly simpler than the old code.
Amusingly, in a normal Release build (which includes the
"assert(L->isLCSSAForm());" assertion), asserting that the result of LCSSA
is in LCSSA form is actually slower than the LCSSA transformation pass
itself on 252.eon. I will see if Loop::isLCSSAForm can be sped up next.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29463 91177308-0d34-0410-b5e6-96231b3b80d8
cases. Ideally, this issue will go away in the future as LCSSA gets smarter
about which Phi nodes it inserts.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29076 91177308-0d34-0410-b5e6-96231b3b80d8
LCSSA is still the slowest pass when gccas'ing 252.eon, but now it only takes
39s instead of 289s. :)
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not handling PHI nodes correctly when determining if a value was live-out.
This patch reduces the number of detected live-out variables in the testcase
from 6565 to 485.
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If a single exit block has multiple predecessors within the loop, it will
appear in the exit blocks list more than once. LCSSA needs to take that into
account so that it doesn't double process that exit block.
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reimplement getValueDominatingFunction to walk the DominanceTree rather than
just searching blindly.
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is now theoretically feature-complete. It has not, however, been thoroughly
test, and is still considered experimental.
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the iterated Dominance Frontier of the loop-closure Phi's. This is the
second phase of the LCSSA pass. The third phase (coming soon) will be to
update all uses of loop variables to use the loop-closure Phi's instead.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28524 91177308-0d34-0410-b5e6-96231b3b80d8
