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
The motivation for this patch is to close the gap between the
VPlan-based CSE and the legacy CSE, to make it easier to remove the
legacy CSE. Before this patch, stubbing out the legacy CSE leads to 22
test failures, and after this patch, there are only 12 failures, and all
of them seem to have a single root cause:
VPlanTransforms::createInterleaveGroups() and
VPInterleaveGroup::execute(). The improvements from this patch are of
course welcome.
While developing the patch, a miscompile was found when GEP
source-element-types differ, and this has been fixed.
Co-authored-by: Florian Hahn <flo@fhahn.com>
Co-authored-by: Luke Lau <luke@igalia.com>
Epilogue vectorization currently relies on the resume phi for the
canonical induction being always available, which is why VPPhi are
considered to have side-effects, to prevent their removal.
This patch adds a new ResumeForEpilogue opcode to mark the resume phi as
used for epilogue vectorization. This allows treating VPPhis in general
as not having side-effects, enabling removal of unused VPPhis.
Materialize the vector trip count computation using VPInstruction
instead of directly creating IR. This is one of the last few steps
needed to model the full vector skeleton in VPlan. It also simplifies
vector-trip count computations for scalable vectors, as we can re-use
the UF x VF computation.
PR: https://github.com/llvm/llvm-project/pull/151925
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
For more powerful folding with operands that are not necessarily
all-constant, use InstSimplifyFolder instead of TargetFolder in
tryToConstantFold, and rename the function tryToFoldLiveIns.
Add an initial CFG simplification transform, which removes the dead
edges for blocks terminated with BranchOnCond true.
At the moment, this removes the edge between middle block and scalar
preheader when folding the tail.
PR: https://github.com/llvm/llvm-project/pull/106748
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
VPExpandSCEVRecipes must be placed in the entry and are alway uniform.
This fixes a crash by always identifying them as uniform, even if the
main vector loop region has been removed.
Fixes https://github.com/llvm/llvm-project/issues/121897.
Update optimizeForVFAndUF to completely remove the vector loop region
when possible. At the moment, we cannot remove the region if it contains
* widened IVs: the recipe is needed to generate the step vector
* reductions: ComputeReductionResults requires the reduction phi recipe
for codegen.
Both cases can be addressed by more explicit modeling.
The patch also includes a number of updates to allow executing VPlans
without a vector loop region.
Depends on https://github.com/llvm/llvm-project/pull/110004
Add missing test coverage of loops where the vector loop region can be
removed that include replicate recipes as well as nested loops.
Extra test coverage for https://github.com/llvm/llvm-project/pull/108378.
Just comparing constant trip counts causes LV to miss cases where the
vector loop body only executes once.
The motivation for this is to remove the need for unrolling to remove
vector loop back-edges, if the body only executes once in more cases.
Reviewed By: Ayal
Differential Revision: https://reviews.llvm.org/D133017
