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
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The commit r225977 uncovered this bug. The problem was that the vectorizer tried to
read the second operand of an already deleted instruction.
The bug didn't show up before r225977 because the freed memory still contained a non-null pointer.
With r225977 deletion of instructions is delayed and the read operand pointer is always null.
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This should be sufficient to replace the initial (minor) function pass
pipeline in Clang with the new pass manager. I'll probably add an (off
by default) flag to do that just to ensure we can get extra testing.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227726 91177308-0d34-0410-b5e6-96231b3b80d8
I've added RUN lines both to the basic test for EarlyCSE and the
target-specific test, as this serves as a nice test that the TTI layer
in the new pass manager is in fact working well.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227725 91177308-0d34-0410-b5e6-96231b3b80d8
Patch by: Igor Laevsky <igor@azulsystems.com>
"Currently SplitBlockPredecessors generates incorrect code in case if basic block we are going to split has a landingpad. Also seems like it is fairly common case among it's users to conditionally call either SplitBlockPredecessors or SplitLandingPadPredecessors. Because of this I think it is reasonable to add this condition directly into SplitBlockPredecessors."
Differential Revision: http://reviews.llvm.org/D7157
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Reduce integer multiplication by a constant of the form k*2^c, where k is in {3,5,9} into a lea + shl. Previously it was only done for imulq on 64-bit platforms, but it makes sense for imull and 32-bit as well.
Differential Revision: http://reviews.llvm.org/D7196
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This patch folds fcmp in some cases of interest in Julia. The patch adds a function CannotBeOrderedLessThanZero that returns true if a value is provably not less than zero. I.e. the function returns true if the value is provably -0, +0, positive, or a NaN. The patch extends InstructionSimplify.cpp to fold instances of fcmp where:
- the predicate is olt or uge
- the first operand is provably not less than zero
- the second operand is zero
The motivation for handling these cases optimizing away domain checks for sqrt in Julia for common idioms such as sqrt(x*x+y*y)..
http://reviews.llvm.org/D6972
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This was introduced in a faulty refactoring (r225640, mea culpa):
the tests weren't testing the return values, so, for both
__strcpy_chk and __stpcpy_chk, we would return the end of the
buffer (matching stpcpy) instead of the beginning (for strcpy).
The root cause was the prefix "__" being ignored when comparing,
which made us always pick LibFunc::stpcpy_chk.
Pass the LibFunc::Func directly to avoid this kind of error.
Also, make the testcases as explicit as possible to prevent this.
The now-useful testcases expose another, entangled, stpcpy problem,
with the further simplification. This was introduced in a
refactoring (r225640) to match the original behavior.
However, this leads to problems when successive simplifications
generate several similar instructions, none of which are removed
by the custom replaceAllUsesWith.
For instance, InstCombine (the main user) doesn't erase the
instruction in its custom RAUW. When trying to simplify say
__stpcpy_chk:
- first, an stpcpy is created (fortified simplifier),
- second, a memcpy is created (normal simplifier), but the
stpcpy call isn't removed.
- third, InstCombine later revisits the instructions,
and simplifies the first stpcpy to a memcpy. We now have
two memcpys.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227250 91177308-0d34-0410-b5e6-96231b3b80d8
Splitting a loop to make range checks redundant is profitable only if
the range check "never" fails. Make this fact a part of recognizing a
range check -- a branch is a range check only if it is expected to
pass (via branch_weights metadata).
Differential Revision: http://reviews.llvm.org/D7192
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This patch teaches the Instruction Combiner how to fold a cttz/ctlz followed by
a icmp plus select into a single cttz/ctlz with flag 'is_zero_undef' cleared.
Added test InstCombine/select-cmp-cttz-ctlz.ll.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227197 91177308-0d34-0410-b5e6-96231b3b80d8
LoopRotate wanted to avoid live range interference by looking at the
uses of a Value in the loop latch and seeing if any lied outside of the
loop. We would wrongly perform this operation on Constants.
This fixes PR22337.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227171 91177308-0d34-0410-b5e6-96231b3b80d8
These tests check that the combination of 227110 (cross block query inst) and 227112 (volatile load semantics) work together properly to allow PRE in cases where a loop contains a volatile access.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227146 91177308-0d34-0410-b5e6-96231b3b80d8
An unreachable default destination can be exploited by other optimizations and
allows for more efficient lowering. Both the SDag switch lowering and
LowerSwitch can exploit unreachable defaults.
Also make TurnSwitchRangeICmp handle switches with unreachable default.
This is kind of separate change, but it cannot be tested without the change
above, and I don't want to land the change above without this since that would
regress other tests.
Differential Revision: http://reviews.llvm.org/D6471
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According to my reading of the LangRef, volatiles are only ordered with respect to other volatiles. It is entirely legal and profitable to forward unrelated loads over the volatile load. This patch implements this for GVN by refining the transition rules MemoryDependenceAnalysis uses when encountering a volatile.
The added test cases show where the extra flexibility is profitable for local dependence optimizations. I have a related change (227110) which will extend this to non-local dependence (i.e. PRE), but that's essentially orthogonal to the semantic change in this patch. I have tested the two together and can confirm that PRE works over a volatile load with both changes. I will be submitting a PRE w/volatiles test case seperately in the near future.
Differential Revision: http://reviews.llvm.org/D6901
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This change is mostly motivated by exposing information about the original query instruction to the actual scanning work in getPointerDependencyFrom when used by GVN PRE. In a follow up change, I will use this to be more precise with regards to the semantics of volatile instructions encountered in the scan of a basic block.
Worth noting, is that this change (despite appearing quite simple) is not semantically preserving. By providing more information to the helper routine, we allow some optimizations to kick in that weren't previously able to (when called from this code path.) In particular, we see that treatment of !invariant.load becomes more precise. In theory, we might see a difference with an ordered/atomic instruction as well, but I'm having a hard time actually finding a test case which shows that.
Test wise, I've included new tests for !invariant.load which illustrate this difference. I've also included some updated TBAA tests which highlight that this change isn't needed for that optimization to kick in - it's handled inside alias analysis itself.
Eventually, it would be nice to factor the !invariant.load handling inside alias analysis as well.
Differential Revision: http://reviews.llvm.org/D6895
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This just lifts the logic into a static helper function, sinks the
legacy pass to be a trivial wrapper of that helper fuction, and adds
a trivial wrapper for the new PM as well. Not much to see here.
I switched a test case to run in both modes, but we have to strip the
dead prototypes separately as that pass isn't in the new pass manager
(yet).
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This is exciting as this is a much more involved port. This is
a complex, existing transformation pass. All of the core logic is shared
between both old and new pass managers. Only the access to the analyses
is separate because the actual techniques are separate. This also uses
a bunch of different and interesting analyses and is the first time
where we need to use an analysis across an IR layer.
This also paves the way to expose instcombine utility functions. I've
got a static function that implements the core pass logic over
a function which might be mildly interesting, but more interesting is
likely exposing a routine which just uses instructions *already in* the
worklist and combines until empty.
I've switched one of my favorite instcombine tests to run with both as
well to make sure this keeps working.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226987 91177308-0d34-0410-b5e6-96231b3b80d8
SimplifyCFG currently does this transformation, but I'm planning to remove that
to allow other passes, such as this one, to exploit the unreachable default.
This patch takes care to keep track of what case values are unreachable even
after the transformation, allowing for more efficient lowering.
Differential Revision: http://reviews.llvm.org/D6697
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This reverts commit r176827.
Björn Steinbrink pointed out that this didn't actually fix the bug
(PR15555) it was attempting to fix.
With this reverted, we can now remove landingpad cleanups that
immediately resume unwinding, converting the invoke to a call.
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There are places where the inductive range check elimination pass
depends on two llvm::Values or llvm::SCEVs to be of the same
llvm::Type when they do not need to be. This patch relaxes those
restrictions (by bailing out of the optimization if the types
mismatch), and adds test cases to trigger those paths.
These issues were found by bootstrapping clang with IRCE running in
the -O3 pass ordering.
Differential Revision: http://reviews.llvm.org/D7082
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ever stored to always use a legal integer type if one is available.
Regardless of whether this particular type is good or bad, it ensures we
don't get weird differences in generated code (and resulting
performance) from "equivalent" patterns that happen to end up using
a slightly different type.
After some discussion on llvmdev it seems everyone generally likes this
canonicalization. However, there may be some parts of LLVM that handle
it poorly and need to be fixed. I have at least verified that this
doesn't impede GVN and instcombine's store-to-load forwarding powers in
any obvious cases. Subtle cases are exactly what we need te flush out if
they remain.
Also note that this IR pattern should already be hitting LLVM from Clang
at least because it is exactly the IR which would be produced if you
used memcpy to copy a pointer or floating point between memory instead
of a variable.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226781 91177308-0d34-0410-b5e6-96231b3b80d8
When two calls from the same MDLocation are inlined they currently get
treated as one inlined function call (creating difficulty debugging,
duplicate variables, etc).
Clang worked around this by including column information on inline calls
which doesn't address LTO inlining or calls to the same function from
the same line and column (such as through a macro). It also didn't
address ctor and member function calls.
By making the inlinedAt locations distinct, every call site has an
explicitly distinct location that cannot be coalesced with any other
call.
This can produce linearly (2x in the worst case where every call is
inlined and the call instruction has a non-call instruction at the same
location) more debug locations. Any increase beyond that are in cases
where the Clang workaround was insufficient and the new scheme is
creating necessary distinct nodes that were being erroneously coalesced
previously.
After this change to LLVM the incomplete workarounds in Clang. That
should reduce the number of debug locations (in a build without column
info, the default on Darwin, not the default on Linux) by not creating
pseudo-distinct locations for every call to an inline function.
(oh, and I made the inlined-at chain rebuilding iterative instead of
recursive because I was having trouble wrapping my head around it the
way it was - open to discussion on the right design for that function
(including going back to a recursive solution))
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The return type of a thunk is meaningless, we just want the arguments
and return value to be forwarded.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226708 91177308-0d34-0410-b5e6-96231b3b80d8
When opt is compiled with AddressSanitizer it takes more than 30 seconds
to unroll the loop in unroll_1M().
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This patch fixes 2 issues in reorderInputsAccordingToOpcode
1) AllSameOpcodeLeft and AllSameOpcodeRight was being calculated incorrectly resulting in code not being vectorized in few cases.
2) Adds logic to reorder operands if we get longer chain of consecutive loads enabling vectorization. Handled the same for cases were we have AltOpcode.
Thanks Michael for inputs and review.
Review: http://reviews.llvm.org/D6677
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IRCE eliminates range checks of the form
0 <= A * I + B < Length
by splitting a loop's iteration space into three segments in a way
that the check is completely redundant in the middle segment. As an
example, IRCE will convert
len = < known positive >
for (i = 0; i < n; i++) {
if (0 <= i && i < len) {
do_something();
} else {
throw_out_of_bounds();
}
}
to
len = < known positive >
limit = smin(n, len)
// no first segment
for (i = 0; i < limit; i++) {
if (0 <= i && i < len) { // this check is fully redundant
do_something();
} else {
throw_out_of_bounds();
}
}
for (i = limit; i < n; i++) {
if (0 <= i && i < len) {
do_something();
} else {
throw_out_of_bounds();
}
}
IRCE can deal with multiple range checks in the same loop (it takes
the intersection of the ranges that will make each of them redundant
individually).
Currently IRCE does not do any profitability analysis. That is a
TODO.
Please note that the status of this pass is *experimental*, and it is
not part of any default pass pipeline. Having said that, I will love
to get feedback and general input from people interested in trying
this out.
This pass was originally r226201. It was reverted because it used C++
features not supported by MSVC 2012.
Differential Revision: http://reviews.llvm.org/D6693
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The change used C++11 features not supported by MSVC 2012. I will fix
the change to use things supported MSVC 2012 and recommit shortly.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226216 91177308-0d34-0410-b5e6-96231b3b80d8
IRCE eliminates range checks of the form
0 <= A * I + B < Length
by splitting a loop's iteration space into three segments in a way
that the check is completely redundant in the middle segment. As an
example, IRCE will convert
len = < known positive >
for (i = 0; i < n; i++) {
if (0 <= i && i < len) {
do_something();
} else {
throw_out_of_bounds();
}
}
to
len = < known positive >
limit = smin(n, len)
// no first segment
for (i = 0; i < limit; i++) {
if (0 <= i && i < len) { // this check is fully redundant
do_something();
} else {
throw_out_of_bounds();
}
}
for (i = limit; i < n; i++) {
if (0 <= i && i < len) {
do_something();
} else {
throw_out_of_bounds();
}
}
IRCE can deal with multiple range checks in the same loop (it takes
the intersection of the ranges that will make each of them redundant
individually).
Currently IRCE does not do any profitability analysis. That is a
TODO.
Please note that the status of this pass is *experimental*, and it is
not part of any default pass pipeline. Having said that, I will love
to get feedback and general input from people interested in trying
this out.
Differential Revision: http://reviews.llvm.org/D6693
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226201 91177308-0d34-0410-b5e6-96231b3b80d8
The bug was introduced in r225282. r225282 assumed that sub X, Y is
the same as add X, -Y. This is not correct if we are going to upgrade
the sub to sub nuw. This change fixes the issue by making the
optimization ignore sub instructions.
Differential Revision: http://reviews.llvm.org/D6979
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it's defined in the current module. Clang generates this situation for the
C++14 sized deallocation functions, because it generates a weak definition in
case one isn't provided by the C++ runtime library.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226069 91177308-0d34-0410-b5e6-96231b3b80d8
The transform is somewhat involved, but the basic idea is simple: find
derived pointers that have been offset from the base pointer using gep
and replace the relocate of the derived pointer with a gep to the
relocated base pointer (with the same offset).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226060 91177308-0d34-0410-b5e6-96231b3b80d8
This commit moves `MDLocation`, finishing off PR21433. There's an
accompanying clang commit for frontend testcases. I'll attach the
testcase upgrade script I used to PR21433 to help out-of-tree
frontends/backends.
This changes the schema for `DebugLoc` and `DILocation` from:
!{i32 3, i32 7, !7, !8}
to:
!MDLocation(line: 3, column: 7, scope: !7, inlinedAt: !8)
Note that empty fields (line/column: 0 and inlinedAt: null) don't get
printed by the assembly writer.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226048 91177308-0d34-0410-b5e6-96231b3b80d8
It turns out, all callsites of the simplifier are guarded by a check for
CallInst::getCalledFunction (i.e., to make sure the callee is direct).
This check wasn't done when trying to further optimize a simplified fortified
libcall, introduced by a refactoring in r225640.
Fix that, add a testcase, and document the requirement.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225895 91177308-0d34-0410-b5e6-96231b3b80d8
Now that the way that the partial unrolling threshold for small loops is used
to compute the unrolling factor as been corrected, a slightly smaller threshold
is preferable. This is expected; other targets may need to re-tune as well.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225566 91177308-0d34-0410-b5e6-96231b3b80d8
When we compute the size of a loop, we include the branch on the backedge and
the comparison feeding the conditional branch. Under normal circumstances,
these don't get replicated with the rest of the loop body when we unroll. This
led to the somewhat surprising behavior that really small loops would not get
unrolled enough -- they could be unrolled more and the resulting loop would be
below the threshold, because we were assuming they'd take
(LoopSize * UnrollingFactor) instructions after unrolling, instead of
(((LoopSize-2) * UnrollingFactor)+2) instructions. This fixes that computation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225565 91177308-0d34-0410-b5e6-96231b3b80d8
The previous code assumed that such instructions could not have any uses
outside CaseDest, with the motivation that the instruction could not
dominate CommonDest because CommonDest has phi nodes in it. That simply
isn't true; e.g., CommonDest could have an edge back to itself.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225552 91177308-0d34-0410-b5e6-96231b3b80d8
