This is just filling in a missing case from D144225.
We treat `(shl Y, X)` and `(shl Z, X)` as `(mul Z, 1 << X)` and `(mul
Y, 1 << X)` then reuse the same transformations that already exist.
Reviewed By: sdesmalen
Differential Revision: https://reviews.llvm.org/D147108
Forked from D142901 to deduce more `nsw`/`nuw` flag for the output
`shl`.
We can handle the following cases + some `nsw`/`nuw` flags:
The rationale for doing this all in `InstCombine` rather than handling
the constant `shl` cases in `InstSimplify` is we often create a new
instruction because we are able to deduce more `nsw`/`nuw` flags than
the original instruction had.
Differential Revision: https://reviews.llvm.org/D144225
Using the more robust log2 search allows us to fold more cases (same
logic as exists for idiv/irem).
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D146347
Unfortunately alive2 cannot prove the correctness due to fails by timeout even for
float type half.
However it should be correct. If a and b are not NaN, maximum and minimum will just
return different values (a and b) and take into account a + b == b + a this is the same.
If a or b is NaN, than maximum and minimum are equal to NaN and NaN + NaN is NaN.
a + b is also a NaN.
In terms of preserving fast flags, we cannot preserve ninf due to
minimum(NaN, Infinity) == maximum(NaN, Infinity) == NaN,
minimum(NaN, Infinity) +ninf maximum(NaN, Infinity) == NaN +ninf NaN = NaN
However transformation will change
minimum(NaN, Infinity) + maximum(NaN, Infinity) to NaN +ninf Infinity == poison.
But if fadd is marked as nnan, we can preserve because NaN +ninf/nnan NaN = poison as well.
The same optimization for
maximum(a,b) * minimum(a,b) => a * b
is added.
All said above for fadd is correct for fmul.
Reviewed By: mkazantsev
Differential Revision: https://reviews.llvm.org/D147299
Revert commit due to failure on buildbot:
error: 'match_combine_or' may not intend to support class template argument deduction
This reverts commit b86a06ef284f2637bef89bf5bb20157a8b195568.
The pair of div folds was just added with:
4966d8ebe1bbe5bd6a4d28
But as noted in the post-commit review, we don't actually need
the no-remainder requirement for an unsigned division (still
need the no-unsigned-wrap though):
https://alive2.llvm.org/ce/z/qHjK3Q
This is a corrected version of:
bc886e9b587b
I made a copy-paste error that created an "add" instead of the
intended "sub" on that attempt. The regression tests showed the
bug, but I overlooked that.
As I said in a comment on issue #58717, the bug reports resulting
from the botched patch confirm that the pattern does occur in
many real-world applications, so hopefully eliminating the multiply
results in better code.
I added one more regression test in this version of the patch,
and here's an Alive2 proof to show that exact example:
https://alive2.llvm.org/ce/z/dge7VC
Original commit message:
This is a sibling to:
6064e92b0a84
...but we canonicalize the shl+add to shl+xor,
so the pattern is different than I expected:
https://alive2.llvm.org/ce/z/8CX16e
I have not found any patterns that are safe
to propagate no-wrap, so that is not included
here.
Differential Revision: https://reviews.llvm.org/D137157
This is a sibling to:
6064e92b0a84
...but we canonicalize the shl+add to shl+xor,
so the pattern is different than I expected:
https://alive2.llvm.org/ce/z/8CX16e
I have not found any patterns that are safe
to propagate no-wrap, so that is not included
here.
X * ((1 << Z) + 1) --> (X << Z) + X
https://alive2.llvm.org/ce/z/P-7WK9
It's possible that we could do better with propagating
no-wrap, but this carries over the existing logic and
appears to be correct.
The naming differences on the existing folds are a result
of using getName() to set the final value via Builder.
That makes it easier to transfer no-wrap rather than the
gymnastics required from the raw create instruction APIs.
If the divisor is a power-of-2 or negative-power-of-2 and the dividend
is known to have >= trailing zeros than the divisor, the division is exact:
https://alive2.llvm.org/ce/z/UGBksM (general proof)
https://alive2.llvm.org/ce/z/D4yPS- (examples based on regression tests)
This isn't the most direct optimization (we could create ashr in these
examples instead of relying on existing folds for exact divides), but
it's possible that there's a more general constraint than just a pow2
divisor, so this might be extended in the future.
This should solve issue #58348.
Differential Revision: https://reviews.llvm.org/D135970
This should be functionally equivalent - both calls are thin
wrappers around computeKnownBits(). We'll probably want to use
known-bits directly in follow-up patches because that could
determine "exact" for example (see issue #58348).
(X << Z) / (Y << Z) --> X / Y
https://alive2.llvm.org/ce/z/CLKzqT
This requires a surprising "nuw" constraint because we have
to guard against immediate UB via signed-div overflow with
-1 divisor.
This extends 008a89037a49ca0d9 and is another transform
derived from issue #58137.
(X << Z) / (Y << Z) --> X / Y
https://alive2.llvm.org/ce/z/E5eaxU
This fixes the motivating example from issue #58137,
but it is not the most general transform. We should
probably also convert left-shift in the divisor to
right-shift in the dividend for that, but that exposes
another missed canonicalization for shifts and adds.
((Op1 * X) / Y) / Op1 --> X / Y
https://alive2.llvm.org/ce/z/JYxWjA
InstSimplify handles the more basic mul+div pattern with
shared operand, but we don't seem to have any reassociation
folds to handle cases where the common op is further away.
This is a generalization of 9cff4711ac72 and another
transform derived from issue #58137.
((X *nuw Y) >> Z) / X --> Y >> Z
https://alive2.llvm.org/ce/z/x3kKnq
This is similar to 6b869be8100d / 8da2fa856f1b, but I have
not found a signed equivalent, so it's just an unsigned
match for now.
The 1st attempt failed to updated the test checks as expected.
Original commit message:
sdiv exact X, (1<<ShAmt) --> ashr exact X, ShAmt (if shl is non-negative)
https://alive2.llvm.org/ce/z/kB6VF7
It would probably be better to use ValueTracking to replace this
and the existing transform above it, but the analysis does not
account for the no-wrap properly, and it's not immediately clear
to me how to fix it.
sdiv exact X, (1<<ShAmt) --> ashr exact X, ShAmt (if shl is non-negative)
https://alive2.llvm.org/ce/z/kB6VF7
It would probably be better to use ValueTracking to replace this
and the existing transform above it, but the analysis does not
account for the no-wrap properly, and it's not immediately clear
to me how to fix it.
This is an unusual canonicalization because we create an extra instruction,
but it's likely better for analysis and codegen (similar reasoning as D133399).
InstCombine::Negator may create this kind of multiply from negate and shift,
but this should not conflict because of the narrow negation.
I don't know how to create a fully general proof for this kind of transform in
Alive2, but here's an example with bitwidths similar to one of the regression
tests:
https://alive2.llvm.org/ce/z/J3jTjR
Differential Revision: https://reviews.llvm.org/D133667
We aleady support the transform: `(X+C1)*CI -> X*CI+C1*CI`
Here the case is a little special as the form of `(X+C1)*CI` is transformed into `(X|C1)*CI`,
so we should also support the transform: `(X|C1)*CI -> X*CI+C1*CI`
Fixes https://github.com/llvm/llvm-project/issues/57278
Reviewed By: bcl5980, spatel, RKSimon
Differential Revision: https://reviews.llvm.org/D132658
Currently, clang ignores the 0 initialisation in finite math
For example:
```
double f_prod = 0;
double arr[1000];
for (size_t i = 0; i < 1000; i++) {
f_prod *= arr[i];
}
```
Clang will ignore that `f_prod` is set to zero and it will generate assembly to iterate over the loop.
Reviewed By: fhahn, spatel
Differential Revision: https://reviews.llvm.org/D131672
