When Sel(Cmp) are in different integer type,
From: (K and N mean width, K < N; a and b are src operands.)
bN = Ext(bK)
cond = Cmp(aN, bN)
aK = Trunc aN
retK = Sel(cond, aK, bK)
To:
bN = Ext(bK)
cond = Cmp(aN, bN)
retN = Sel(cond, aN, bN)
retK = Trunc retN
Though Sel's operands width becomes larger, the benefit
of making type width in Sel the same as Cmp, is for combing
to max/min intrinsics, and also better performance for SIMD
instructions.
References of correctness: https://alive2.llvm.org/ce/z/Y4Kegmhttps://alive2.llvm.org/ce/z/qFtjtR
Reference of generated code comparision:
https://gcc.godbolt.org/z/o97svGvYMhttps://gcc.godbolt.org/z/59Ynj91ov
We would like to optimize situations of the form that happen after loop
vectorization+SROA:
```
loop:
%phi = phi zeroinitializer, %interleaved
%deinterleave_a = shufflevector %phi, poison ; pick half of the lanes
%deinterleave_b = shufflevector %phi, posion ; pick remaining lanes
... %a = ... %b = ...
%interleaved = shufflevector %a, %b ; interleave lanes of a+b
```
where the interleave and de-interleave shuffle operations cancel each
other out.
This could be handled by `foldOpPhi` but does not currently work because
it does
not proceed when there are multiple uses of the `Phi` operation.
This extends `foldOpPhi` to allow multiple `shufflevector` uses when
they are
shown to simplify for all `Phi` input values.
When using non-integral pointer types, such as on CHERI targets, size_t
is equivalent
to the index size, which is allowed to be smaller than the size of the
pointer.
When we have a gep inbounds from the base of an object (e.g. alloca or
global), we know that the index cannot be negative, as this would go out
of bounds. As such, we can infer nuw as well.
The implementation is a bit stricter than necessary, we could also
accept one unknown index followed by known-non-negative indices.
Proof: https://alive2.llvm.org/ce/z/Hp7-6w (Note that alive2 currently
incorrectly doesn't require the inbounds for the alloca case, see
https://github.com/AliveToolkit/alive2/issues/1138).
The main goal is to fold away wave64 code when compiled for wave32.
If we have out of bounds indexing, these will now clamp down to
a low bit which may CSE with the operations on the low half of the
wave.
These combines involve swapping the fptrunc with its operand, and using
the intersection of fast math flags is the safest option as e.g. if we
have (fptrunc (fneg ninf x)) then (fneg ninf (fptrunc x)) will not be
correct as if x is a not within the range of the destination type the
result of (fptrunc x) will be inf.
Writing a test for this transitively exposed a number of places in
BuildLibCalls where
we were failing to propagate address spaces properly, which are
additionally fixed.
The following pattern: `(C2 << X) << C1` will usually be transformed
into `(C2 << C1) << X`, essentially swapping `X` and `C1`.
However, this should only be done when `C1` is an immediate constant,
otherwise thiscan lead to both constants being swapped forever.
This fixes#118798.
This consists of:
* Make these instructions part of FPMathOperator.
* Adjust bitcode/ir readers/writers to expect fast math flags on these
instructions.
* Make IRBuilder set the fast math flags on these instructions.
* Update langref and release notes.
* Update a bunch of tests. Some of these are due to InstCombineCasts
incorrectly adding fast math flags to fptrunc, which will be fixed in a
later patch.
Unsigned icmp of gep nuw folds to unsigned icmp of offsets. Unsigned
icmp of gep nusw nuw folds to unsigned samesign icmp of offsets.
Proofs: https://alive2.llvm.org/ce/z/VEwQY8
We had a separate fold that handled just the trivial case where we're
replacing exactly the argument of the select. Handle this in select
value equivalence by relaxing the infinite loop protection to allow a
replacement of a non-constant with a constant.
This also fixes https://github.com/llvm/llvm-project/issues/113301, as
the separate fold did not handle undef values correctly.
Preserve !alias.scope, !noalias and !mem.parallel_loop_access metadata
on the replacement instruction, if it does not move. In that case, the
program would be UB, if the aliasing property encoded in the metadata
does not hold. This makes use of the clarification re aliasing metadata
implying UB if the property does not hold: #116220
Same as #115868, but for !alias.scope, !noalias and
!mem.parallel_loop_access.
PR: https://github.com/llvm/llvm-project/pull/117716
