This patch canonicalizes getelementptr instructions with constant
indices to use the `i8` source element type. This makes it easier for
optimizations to recognize that two GEPs are identical, because they
don't need to see past many different ways to express the same offset.
This is a first step towards
https://discourse.llvm.org/t/rfc-replacing-getelementptr-with-ptradd/68699.
This is limited to constant GEPs only for now, as they have a clear
canonical form, while we're not yet sure how exactly to deal with
variable indices.
The test llvm/test/Transforms/PhaseOrdering/switch_with_geps.ll gives
two representative examples of the kind of optimization improvement we
expect from this change. In the first test SimplifyCFG can now realize
that all switch branches are actually the same. In the second test it
can convert it into simple arithmetic. These are representative of
common optimization failures we see in Rust.
Fixes https://github.com/llvm/llvm-project/issues/69841.
Relative to the previous attempt, this is rebased over the
InstSimplify fix in ac74e7a7806480a000c9a3502405c3dedd8810de,
which addresses the miscompile reported in PR58401.
-----
foldOpIntoPhi() currently only folds operations into the phi if all
but one operands constant-fold. The two exceptions to this are freeze
and select, where we allow more general simplification.
This patch makes foldOpIntoPhi() generally simplification based and
removes all the instruction-specific logic. We just try to simplify
the instruction for each operand, and for the (potentially) one
non-simplified operand, we move it into the new block with adjusted
operands.
This fixes https://github.com/llvm/llvm-project/issues/57448, which
was my original motivation for the change.
Differential Revision: https://reviews.llvm.org/D134954
Relative to the previous attempt, this adjusts simplification to
use the correct context instruction: We need to use the terminator
of the incoming block, not the original instruction.
-----
foldOpIntoPhi() currently only folds operations into the phi if all
but one operands constant-fold. The two exceptions to this are freeze
and select, where we allow more general simplification.
This patch makes foldOpIntoPhi() generally simplification based and
removes all the instruction-specific logic. We just try to simplify
the instruction for each operand, and for the (potentially) one
non-simplified operand, we move it into the new block with adjusted
operands.
This fixes https://github.com/llvm/llvm-project/issues/57448, which
was my original motivation for the change.
Differential Revision: https://reviews.llvm.org/D134954
The infinite loop seen on buildbots should be fixed by
11897708c0229c92802e747564e7c34b722f045f (assuming there are not
multiple infinite combine loops...)
-----
foldOpIntoPhi() currently only folds operations into the phi if all
but one operands constant-fold. The two exceptions to this are freeze
and select, where we allow more general simplification.
This patch makes foldOpIntoPhi() generally simplification based and
removes all the instruction-specific logic. We just try to simplify
the instruction for each operand, and for the (potentially) one
non-simplified operand, we move it into the new block with adjusted
operands.
This fixes https://github.com/llvm/llvm-project/issues/57448, which
was my original motivation for the change.
Differential Revision: https://reviews.llvm.org/D134954
Reapply with a fix for the case where an operand simplified back
to the original phi: We need to map this case to the new phi node.
-----
foldOpIntoPhi() currently only folds operations into the phi if all
but one operands constant-fold. The two exceptions to this are freeze
and select, where we allow more general simplification.
This patch makes foldOpIntoPhi() generally simplification based and
removes all the instruction-specific logic. We just try to simplify
the instruction for each operand, and for the (potentially) one
non-simplified operand, we move it into the new block with adjusted
operands.
This fixes https://github.com/llvm/llvm-project/issues/57448, which
was my original motivation for the change.
foldOpIntoPhi() currently only folds operations into the phi if all
but one operands constant-fold. The two exceptions to this are freeze
and select, where we allow more general simplification.
This patch makes foldOpIntoPhi() generally simplification based and
removes all the instruction-specific logic. We just try to simplify
the instruction for each operand, and for the (potentially) one
non-simplified operand, we move it into the new block with adjusted
operands.
This fixes https://github.com/llvm/llvm-project/issues/57448, which
was my original motivation for the change.
This patch tries to sink instructions when they are only used in a successor block.
This is a further enhancement patch based on Anna's commit:
D109700, which allows sinking an instruction having multiple uses in a single user.
In this patch, sink instructions with multiple users in a single successor block will be supported.
It could fix a known issue from rust:
https://github.com/rust-lang/rust/issues/51346#issuecomment-394443610
Reviewed By: nikic, reames
Differential Revision: https://reviews.llvm.org/D121585
As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
Eliminate inttype phi with inttoptr/ptrtoint.
This version fixed a bug in finding the matching
phi -- the order of the incoming blocks may be
different (triggered in self build on Windows).
A new test case is added.
llvm-svn: 315272
