https://alive2.llvm.org/ce/z/o7rQ5q
This shows an extra instruction in some cases, but that is
caused by an existing canonicalization of trunc -> and+icmp.
Codegen should be better for any target where a multiply is
more costly than the most simple ALU op.
This ends up producing the requested x86 asm from issue #55618,
but it's not the same IR. We are missing a canonicalization
from the negate+mask pattern to the trunc+select created here.
(ashr i32 X, 31) * C --> (X < 0) ? -C : 0
https://alive2.llvm.org/ce/z/G8u9SS
With a constant operand, this is an improvement in IR
and codegen (where it can be converted to a mask op).
Without a constant operand, we would have to negate
the operand, so that is probably better left to the backend.
This is similar but not the same optimization that is requested
in #55618.
We already have the related folds for zext-of-bool, so it
should make things more consistent to have this transform
to select for sext-of-bool too:
https://alive2.llvm.org/ce/z/YikdfAFixes#53319
(iN X s>> (N-1)) & Y --> (X < 0) ? Y : 0
https://alive2.llvm.org/ce/z/qeYhdz
I was looking at a missing abs() transform and found my way to this
generalization of an existing fold that was added with D67799.
As discussed in that review, we want to make sure codegen handles
this difference well, and for all of the targets/types that I
spot-checked, it looks good.
I am leaving the existing fold in place in this commit because
it covers a potentially missing icmp fold, but I plan to remove
that as a follow-up commit as suggested during review.
Differential Revision: https://reviews.llvm.org/D111410
InstCombine didn't perform (sext bool X) * (sext bool X) --> zext (and X, X) which can result in just (zext X). The patch adds regression tests to check this transformation and adds a check for equality of mul's operands for that case.
Differential Revision: https://reviews.llvm.org/D104193
InstCombine didn't perform (sext bool X) * (sext bool X) --> zext (and X, X) which can result in just (zext X). The patch adds regression tests to check this transformation and adds a check for equality of mul's operands for that case.
Differential Revision: https://reviews.llvm.org/D104193
While x*undef is undef, shift-by-undef is poison,
which we must avoid introducing.
Also log2(iN undef) is *NOT* iN undef, because log2(iN undef) u< N.
See https://bugs.llvm.org/show_bug.cgi?id=47133
Negator knows how to do this, but the one-use reasoning is getting
a bit muddy here, we don't really want to increase instruction count,
so we need to both lie that "IsNegation" and have an one-use check
on the outermost LHS value.
Multiplication is commutative, and either of operands can be negative,
so if the RHS is a negated power-of-two, we should try to make it
true power-of-two (which will allow us to turn it into a left-shift),
by trying to sink the negation down into LHS op.
But, we shouldn't re-invent the logic for sinking negation,
let's just use Negator for that.
Tests and original patch by: Simon Pilgrim @RKSimon!
Differential Revision: https://reviews.llvm.org/D85446
Similar to rG40fcc42:
The base case only worked because we were relying on a
poison-unsafe select transform; if that is fixed, we
would regress on patterns like this.
The extra use tests show that the select transform can't
be applied consistently. So it may be a regression to have
an extra instruction on 1 test, but that result was not
created safely and does not happen reliably.
The base case only works because we are relying on a
poison-unsafe select transform; if that is fixed, we
would regress on patterns like this.
The extra use tests show that the select transform can't
be applied consistently. So it may be a regression to have
an extra instruction on 1 test, but that result was not
created safely and does not happen reliably.
Summary:
SimplifySelectsFeedingBinaryOp simplified binary ops when both operands
were selects with the same condition. This patch extends it to handle
these cases where only one operand is a select:
X op (C ? P : Q) -> C ? (X op P) : (X op Q)
// if X op P and X op Q both simplify
(C ? P : Q) op Y -> C ? (P op Y) : (Q op Y)
// if P op Y and Q op Y both simplify
For example: X *fast (C ? 1.0 : 0.0) -> C ? X : 0.0
Reviewers: mcberg2017, majnemer, craig.topper, qcolombet, mcrosier
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D64713
As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
For vectors, getPrimitiveSizeInBits returns the full vector width. This code should using the element size for vectors. This could be fixed by calling getScalarSizeInBits, but its even easier to just get it from the APInt we're checking.
Differential Revision: https://reviews.llvm.org/D51938
llvm-svn: 341971
This replaces the bit-tracking based fold that did the same thing,
but it only worked for scalars and not directly.
There is no evidence in existing regression tests that the greater
power of bit-tracking was needed here, but we should be aware of
this potential loss of optimization.
llvm-svn: 325062
The scalar folds are done indirectly and use potentially
expensive value tracking calls. That can be improved
along with the enhancement to support vector types.
llvm-svn: 325051
This is both a functional improvement for vectors and an
efficiency improvement for scalars. The existing code below
the new folds does the same thing for scalars, but in an
indirect and expensive way.
llvm-svn: 325048
The InstCombine integer mul test file had tests that belong in InstSimplify
(including fmul tests). Move things to where they belong and auto-generate
complete checks for everything.
llvm-svn: 325037
The check to see if we can propagate the nsw flag used m_ConstantInt(uint64_t*&) which doesn't work with splat vectors and has a restriction that the bitwidth of the ConstantInt must be 64-bits are less.
This patch changes it to use m_APInt to remove both these issues
Differential Revision: https://reviews.llvm.org/D34699
llvm-svn: 306457
Sanjay Patel