16 Commits

Author SHA1 Message Date
Florian Hahn
98d3a25f74
[VPlan] Don't preserve LCSSA in expandSCEVs. (#165505)
This follows similar reasoning as 45ce88758d24
(https://github.com/llvm/llvm-project/pull/159556):

LV does not preserve LCSSA, it constructs it just before processing a
loop to vectorize. Runtime check expressions are invariant to that loop,
so expanding them should not break LCSSA form for the loop we are about
to vectorize.

LV creates SCEV and memory runtime checks early on and then disconnects
the blocks temporarily. The patch fixes a mis-compile, where previously
LCSSA construction during SCEV expand may replace uses in currently
unreachable SCEV/memory check blocks.

Fixes https://github.com/llvm/llvm-project/issues/162512

PR: https://github.com/llvm/llvm-project/pull/165505
2025-10-29 18:25:46 +00:00
Florian Hahn
8907b6d393
[VPlan] Remove original loop blocks if dead. (#155497)
Build on top of https://github.com/llvm/llvm-project/pull/154510 to
completely remove the blocks of dead scalar loops.

Depends on https://github.com/llvm/llvm-project/pull/154510. 

PR: https://github.com/llvm/llvm-project/pull/155497
2025-10-01 16:53:59 +00:00
Florian Hahn
50b9ca4dda
[VPlan] Simplify Plan's entry in removeBranchOnConst. (#154510)
After https://github.com/llvm/llvm-project/pull/153643, there may be a
BranchOnCond with constant condition in the entry block.

Simplify those in removeBranchOnConst. This removes a number of
redundant conditional branch from entry blocks.

In some cases, it may also make the original scalar loop unreachable,
because we know it will never execute. In that case, we need to remove
the loop from LoopInfo, because all unreachable blocks may dominate each
other, making LoopInfo invalid. In those cases, we can also completely
remove the loop, for which I'll share a follow-up patch.

Depends on https://github.com/llvm/llvm-project/pull/153643.

PR: https://github.com/llvm/llvm-project/pull/154510
2025-09-18 19:25:05 +01:00
Florian Hahn
351d398a37
[VPlan] Run final VPlan simplifications before codegen.
Dissolving the hierarchical VPlan CFG and converting abstract to
concrete recipes can expose additional simplification opportunities.

Do a final run of simplifyRecipes before executing the VPlan.
2025-08-16 18:54:27 +01:00
Florian Hahn
89ae085859
[VPlan] Remove VPVectorPointer for part 0 after unrolling. (#149735)
VPVectorPointer for part 0 is just the pointer operand. Simplify it
after unrolling. This removes a large number of redundant GEPs with
index 0.

PR: https://github.com/llvm/llvm-project/pull/149735
2025-07-27 13:53:26 +01:00
Florian Hahn
fa3ec0c17c
[VPlan] Materialize constant vector trip counts before final opts. (#142309)
Materialize constant vector trip counts before ::execute, if the trip
count can be computed as Original (TC / (VF * UF)) * (VF * UF). For now
this excludes when the tail is folded or scalar epilogues are required.

This enables removing a number of redundant branches from the middle
block.

For now this is also only done when not vectorizing the epilogue, as the
simplification complicates stitching the 2 plans together.

PR: https://github.com/llvm/llvm-project/pull/142309
2025-07-26 17:16:36 +01:00
Florian Hahn
dfca6c0d3b
[VPlan] Remove no-op SCALAR-STEPS after unrolling. (#123655)
After unrolling, there may be additional simplifications that can be
applied. One example is removing SCALAR-STEPS for the first part where
only the first lane is demanded.

This removes redundant adds of 0 from a large number of tests (~200),
many which I am still working on updating.

In preparation for removing redundant WideIV steps added in
https://github.com/llvm/llvm-project/pull/119284.

PR: https://github.com/llvm/llvm-project/pull/123655
2025-03-25 12:57:24 +00:00
Florian Hahn
e5f5517f91 [VPlan] Create IR basic block for middle.block in VPlan.
Create a IR BB directly for the middle.block, instead of creating the IR
BB during skeleton creation and then replacing the middle VPBB with a
VPIRBB.

This moves another part of skeleton creation to VPlan and simplififes
the code slightly by removing code to disconnect the middle block and
vector preheader + the corresponding DT update.

NFC modulo IR block naming and block creation order, which changes the
IR names for the blocks.
2025-02-15 21:54:16 +01:00
Florian Hahn
32c4493d5f
[VPlan] Add incoming values for all predecessor to ResumePHI (NFCI).
Follow-up as discussed when using VPInstruction::ResumePhi for all resume
values (#112147). This patch explicitly adds incoming values for each
predecessor in VPlan. This simplifies codegen and allows transformations
adjusting the predecessors of blocks with

NFC modulo incoming block order in phis.
2025-02-09 11:20:20 +00:00
Florian Hahn
df8efbdbbf
[SCEV] Remove existing predicates implied by newly added ones. (#118185)
When adding a new predicate to a union predicate, some of the existing
predicates may be implied by the new predicate. Remove any existing
predicates that are already implied by the new predicate.

Depends on https://github.com/llvm/llvm-project/pull/118184 to show the
main benefit.

PR: https://github.com/llvm/llvm-project/pull/118185
2024-12-20 20:49:37 +00:00
Florian Hahn
4ad0fdd163
[VPlan] Remove reverse() of predecessors from VPInstruction::generate.
This was originally done to reduce the diff for the change. Remove it
and update the remaining tests. NFC modulo reordering of incoming
values.

Clean up after https://github.com/llvm/llvm-project/pull/114292.
2024-12-17 20:44:32 +00:00
Florian Hahn
7f7f540a48
Reapply "[VPlan] Update scalar induction resume values in VPlan. (#110577)"
This reverts commit f09b16e2671cbcdf7cb7dc7ed705db092a9deda1.

The crash when building llvm-test-suite with stage2 should have been
fixed by 1091fad31a83d5ab87eb6fa11fe3bdb3f0d152ea.
2024-12-06 19:41:51 +00:00
Nikita Popov
f09b16e267 Revert "[VPlan] Update scalar induction resume values in VPlan. (#110577)"
This reverts commit 0678e2058364ec10b94560d27ec7138dfa003287.
This reverts commit 1091fad31a83d5ab87eb6fa11fe3bdb3f0d152ea.

Causes crashes in llvm-test-suite when using stage 2 clang.
2024-12-06 18:01:42 +01:00
Florian Hahn
0678e20583
[VPlan] Update scalar induction resume values in VPlan. (#110577)
Updated ILV.createInductionResumeValues (now createInductionResumeVPValue)
to directly update the VPIRInstructions wrapping the original phis with the 
created resume values.

This is the first step towards modeling them completely in VPlan.
Subsequent patches will move creation of the resume values completely
into VPlan.

Depends on https://github.com/llvm/llvm-project/pull/109975.

PR: https://github.com/llvm/llvm-project/pull/110577
2024-12-06 12:26:19 +00:00
Florian Hahn
96e83d3705
[LV] Use IRBuilder to create and optimize middle-block compare.
Split off from D150398 to avoid builder-related diff changes there.
Using IRBuilder to create ICmps simplifies the result if both operands
are constants.

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D158332
2023-08-29 11:42:18 +01:00
Florian Hahn
1746ac42ca
[LV] Forget SCEVs for exit phis after vectorization.
After vectorization, the exit blocks of the original loop will have additional
predecessors. Invalidate SCEVs for the exit phis in case SE looked through
single-entry phis.

Fixes https://github.com/llvm/llvm-project/issues/63368
Fixes https://github.com/llvm/llvm-project/issues/63669
2023-07-04 21:28:03 +01:00