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dbaeb6e7cb
Runtime unrolling will create a prologue to execute the extra
iterations which is can't divided by the unroll factor. It
generates an if-then-else sequence to jump into a factor -1
times unrolled loop body, like
extraiters = tripcount % loopfactor
if (extraiters == 0) jump Loop:
if (extraiters == loopfactor) jump L1
if (extraiters == loopfactor-1) jump L2
...
L1: LoopBody;
L2: LoopBody;
...
if tripcount < loopfactor jump End
Loop:
...
End:
It means if the unroll factor is 4, the loop body will be 7
times unrolled, 3 are in loop prologue, and 4 are in the loop.
This commit is to use a loop to execute the extra iterations
in prologue, like
extraiters = tripcount % loopfactor
if (extraiters == 0) jump Loop:
else jump Prol
Prol: LoopBody;
extraiters -= 1 // Omitted if unroll factor is 2.
if (extraiters != 0) jump Prol: // Omitted if unroll factor is 2.
if (tripcount < loopfactor) jump End
Loop:
...
End:
Then when unroll factor is 4, the loop body will be copied by
only 5 times, 1 in the prologue loop, 4 in the original loop.
And if the unroll factor is 2, new loop won't be created, just
as the original solution.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218604 91177308-0d34-0410-b5e6-96231b3b80d8
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|---|---|---|
| .. | ||
| PowerPC | ||
| X86 | ||
| 2004-05-13-DontUnrollTooMuch.ll | ||
| 2005-03-06-BadLoopInfoUpdate.ll | ||
| 2006-08-24-MultiBlockLoop.ll | ||
| 2007-04-16-PhiUpdate.ll | ||
| 2007-05-05-UnrollMiscomp.ll | ||
| 2007-05-09-UnknownTripCount.ll | ||
| 2007-11-05-Crash.ll | ||
| 2011-08-08-PhiUpdate.ll | ||
| 2011-08-09-IVSimplify.ll | ||
| 2011-08-09-PhiUpdate.ll | ||
| 2011-10-01-NoopTrunc.ll | ||
| 2012-04-09-unroll-indirectbr.ll | ||
| basic.ll | ||
| ephemeral.ll | ||
| ignore-annotation-intrinsic-cost.ll | ||
| loop-remarks.ll | ||
| partial-unroll-optsize.ll | ||
| pr10813.ll | ||
| pr11361.ll | ||
| pr14167.ll | ||
| pr18861.ll | ||
| runtime-loop1.ll | ||
| runtime-loop2.ll | ||
| runtime-loop3.ll | ||
| runtime-loop.ll | ||
| scevunroll.ll | ||
| shifted-tripcount.ll | ||
| unloop.ll | ||
| unroll-pragmas-disabled.ll | ||
| unroll-pragmas.ll | ||