Commit Graph

16 Commits

Author SHA1 Message Date
Shawn Landden 24f4085811 [SimplifyCFG] NFC, update Switch tests as a baseline.
Also add baseline tests to show effect of later patches.

There were a couple of regressions here that were never caught,
but my patch set that this is a preparation to will fix them.

This is the third attempt to land this patch.

Differential Revision: https://reviews.llvm.org/D61150

llvm-svn: 363319
2019-06-13 19:36:38 +00:00
Shawn Landden 8b142bcc3f [SimplifyCFG] reverting preliminary Switch patches again
This reverts 363226 and 363227, both NFC intended

I swear I fixed the test case that is failing, and ran
the tests, but I will look into it again.

llvm-svn: 363229
2019-06-13 05:26:17 +00:00
Shawn Landden c54b2011bd [SimplifyCFG] NFC, update Switch tests to better examine successive patches
Also add baseline tests to show effect of later patches.

There were a couple of regressions here that were never caught,
but my patch set that this is a preparation to will fix them.

Differential Revision: https://reviews.llvm.org/D61150

llvm-svn: 363226
2019-06-13 04:51:35 +00:00
Shawn Landden c6cba2957d [SimplifyCFG] revert the last commit.
I ran ALL the test suite locally, so I will look into this...

llvm-svn: 363223
2019-06-13 02:47:47 +00:00
Shawn Landden f93b99b2b6 [SimplifyCFG] NFC, update Switch tests to HEAD so I can
see if my changes change anything

Also add baseline tests to show effect of later patches.

Differential Revision: https://reviews.llvm.org/D61150

llvm-svn: 363222
2019-06-13 02:24:24 +00:00
Shawn Landden 2ee9a827ad [SimplifyCFG] fix last commit
llvm-svn: 362501
2019-06-04 14:32:52 +00:00
Shawn Landden 7f22fecac2 [SimplifyCFG] NFC; remove bogus test case
Even if one bit is defined, the code is not clear what it is suppose to do.

The test wants to assert that some bits are undef, but that's not what the IR does and I don't think it's even possible to do that in any meaningful way. It was added in D12497, so @reames might want to double check.

Differential Revision: https://reviews.llvm.org/D60859

llvm-svn: 362499
2019-06-04 14:17:46 +00:00
Shawn Landden 343578759e [SimplifyCFG] back out all SwitchInst commits
They caused the sanitizer builds to fail.

My suspicion is the change the countLeadingZeros().

llvm-svn: 361736
2019-05-26 18:15:51 +00:00
Shawn Landden 30111c786f [SimplifyCFG] Run ReduceSwitchRange unconditionally, generalize
Rather than gating on "isSwitchDense" (resulting in necessesarily
sparse lookup tables even when they were generated), always run
this quite cheap transform.

This transform is useful not just for generating tables.
LowerSwitch also wants this: read LowerSwitch.cpp:257.

Be careful to not generate worse code, by introducing a
SubThreshold heuristic.

Instead of just sorting by signed, generalize the finding of the
best base.

And now that it is run unconditionally, do not replicate its
functionality in SwitchToLookupTable (which could use a Sub
when having a hole is smaller, hence the SubThreshold
heuristic located in a single place).
This simplifies SwitchToLookupTable, and fixes
some ugly corner cases due to the use of signed numbers,
such as a table containing i16 32768 and 32769, of which
32769 would be interpreted as -32768, and now the code thinks
the table is size 65536.

(We still use unconditional subtraction when building a single-register mask,
but I think this whole block should go when the more general sparse
map is added, which doesn't leave empty holes in the table.)

And the reason test4 and test5 did not trigger was documented wrong:
it was because they were not considered sufficiently "dense".

Also, fix generation of invalid LLVM-IR: shl by bit-width.

llvm-svn: 361727
2019-05-26 13:55:14 +00:00
Shawn Landden 50c73a044f [SimplifyCFG] NFC, update Switch tests to HEAD so I can see if my changes change anything
Also add baseline tests to show effect of later patches.

llvm-svn: 361725
2019-05-26 13:52:41 +00:00
Eric Christopher cee313d288 Revert "Temporarily Revert "Add basic loop fusion pass.""
The reversion apparently deleted the test/Transforms directory.

Will be re-reverting again.

llvm-svn: 358552
2019-04-17 04:52:47 +00:00
Eric Christopher a863435128 Temporarily Revert "Add basic loop fusion pass."
As it's causing some bot failures (and per request from kbarton).

This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.

llvm-svn: 358546
2019-04-17 02:12:23 +00:00
Daniel Jasper aec2fa352f Revert @llvm.assume with operator bundles (r289755-r289757)
This creates non-linear behavior in the inliner (see more details in
r289755's commit thread).

llvm-svn: 290086
2016-12-19 08:22:17 +00:00
Hal Finkel cb9f78e1c3 Make processing @llvm.assume more efficient by using operand bundles
There was an efficiency problem with how we processed @llvm.assume in
ValueTracking (and other places). The AssumptionCache tracked all of the
assumptions in a given function. In order to find assumptions relevant to
computing known bits, etc. we searched every assumption in the function. For
ValueTracking, that means that we did O(#assumes * #values) work in InstCombine
and other passes (with a constant factor that can be quite large because we'd
repeat this search at every level of recursion of the analysis).

Several of us discussed this situation at the last developers' meeting, and
this implements the discussed solution: Make the values that an assume might
affect operands of the assume itself. To avoid exposing this detail to
frontends and passes that need not worry about it, I've used the new
operand-bundle feature to add these extra call "operands" in a way that does
not affect the intrinsic's signature. I think this solution is relatively
clean. InstCombine adds these extra operands based on what ValueTracking, LVI,
etc. will need and then those passes need only search the users of the values
under consideration. This should fix the computational-complexity problem.

At this point, no passes depend on the AssumptionCache, and so I'll remove
that as a follow-up change.

Differential Revision: https://reviews.llvm.org/D27259

llvm-svn: 289755
2016-12-15 02:53:42 +00:00
Philip Reames 053701399d [SimplifyCFG] Use known bits to eliminate dead switch defaults
This is a follow up to http://reviews.llvm.org/D11995 implementing the suggestion by Hans.

If we know some of the bits of the value being switched on, we know that the maximum number of unique cases covers the unknown bits. This allows to eliminate switch defaults for large integers (i32) when most bits in the value are known.

Note that I had to make the transform contingent on not having any dead cases. This is conservatively correct with the old code, but required for the new code since we might have a dead case which varies one of the known bits. Counting that towards our number of covering cases would be bad.  If we do have dead cases, we'll eliminate them first, then revisit the possibly dead default.

Differential Revision: http://reviews.llvm.org/D12497

llvm-svn: 247309
2015-09-10 17:44:47 +00:00
Philip Reames 98a2dabc08 [SimplifyCFG] Prune code from a provably unreachable switch default
As Sanjoy pointed out over in http://reviews.llvm.org/D11819, a switch on an icmp should always be able to become a branch instruction. This patch generalizes that notion slightly to prove that the default case of a switch is unreachable if the cases completely cover all possible bit patterns in the condition. Once that's done, the switch to branch conversion kicks in just fine.

Note: Duplicate case values are disallowed by the LangRef and verifier.

Differential Revision: http://reviews.llvm.org/D11995

llvm-svn: 246125
2015-08-26 23:56:46 +00:00