Summary:
This allows other passes (such as SLSR) to compute the SCEV expression for an
imaginary GEP.
Test Plan: no regression
Reviewers: atrick, sanjoy
Reviewed By: sanjoy
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D9786
llvm-svn: 237589
Summary:
Consider (B | i) * S as (B + i) * S if B and i have no bits set in
common.
Test Plan: @or in slsr-mul.ll
Reviewers: broune, meheff
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D9788
llvm-svn: 237456
Summary:
After we rewrite a candidate, the instructions used by the old form may
become unused. This patch cleans up these unused instructions so that we
needn't run DCE after SLSR.
Test Plan: removed -dce in all the SLSR tests
Reviewers: broune, meheff
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D9101
llvm-svn: 235410
Summary:
With this patch, SLSR may rewrite
S1: X = B + i * S
S2: Y = B + i' * S
to
S2: Y = X + (i' - i) * S
A secondary improvement: if (i' - i) is a power of 2, emit Y as X + (S << log(i' - i)). (S << log(i' -i)) is in a canonical form and thus more likely GVN'ed than (i' - i) * S.
Test Plan: slsr-add.ll
Reviewers: hfinkel, sanjoy, meheff, broune, eliben
Reviewed By: eliben
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D8983
llvm-svn: 235019
The plan here is to push the API changes out from the common components
(like Constant::getGetElementPtr and IRBuilder::CreateGEP related
functions) and just update callers to either pass the type if it's
obvious, or pass null.
Do this with LoadInst as well and anything else that comes up, then to
start porting specific uses to not pass null anymore - this may require
some refactoring in each case.
llvm-svn: 234042
Summary:
The old requirement on GEP candidates being in bounds is unnecessary.
For off-bound GEPs, we still have
&B[i * S] = B + (i * S) * e = B + (i * e) * S
Test Plan: slsr_offbound_gep in slsr-gep.ll
Reviewers: meheff
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D8809
llvm-svn: 233949
Summary:
This patch enhances SLSR to handle another candidate form &B[i * S]. If
we found two candidates
S1: X = &B[i * S]
S2: Y = &B[i' * S]
and S1 dominates S2, we can replace S2 with
Y = &X[(i' - i) * S]
Test Plan:
slsr-gep.ll
X86/no-slsr.ll: verify that we do not run SLSR on GEPs that already fit into
an addressing mode
Reviewers: eliben, atrick, meheff, hfinkel
Reviewed By: hfinkel
Subscribers: sanjoy, llvm-commits
Differential Revision: http://reviews.llvm.org/D7459
llvm-svn: 233286
Summary:
Straight-line strength reduction (SLSR) is implemented in GCC but not yet in
LLVM. It has proven to effectively simplify statements derived from an unrolled
loop, and can potentially benefit many other cases too. For example,
LLVM unrolls
#pragma unroll
foo (int i = 0; i < 3; ++i) {
sum += foo((b + i) * s);
}
into
sum += foo(b * s);
sum += foo((b + 1) * s);
sum += foo((b + 2) * s);
However, no optimizations yet reduce the internal redundancy of the three
expressions:
b * s
(b + 1) * s
(b + 2) * s
With SLSR, LLVM can optimize these three expressions into:
t1 = b * s
t2 = t1 + s
t3 = t2 + s
This commit is only an initial step towards implementing a series of such
optimizations. I will implement more (see TODO in the file commentary) in the
near future. This optimization is enabled for the NVPTX backend for now.
However, I am more than happy to push it to the standard optimization pipeline
after more thorough performance tests.
Test Plan: test/StraightLineStrengthReduce/slsr.ll
Reviewers: eliben, HaoLiu, meheff, hfinkel, jholewinski, atrick
Reviewed By: jholewinski, atrick
Subscribers: karthikthecool, jholewinski, llvm-commits
Differential Revision: http://reviews.llvm.org/D7310
llvm-svn: 228016
Jingyue Wu