Commit Graph

355 Commits

Author SHA1 Message Date
zhoujing e6ae0f7ac6 [VENTUS][RISCV][fix] Disable simple loop optimization to call llvm memset/memcpy intrinsics 2023-07-11 16:26:49 +08:00
Nikita Popov b128e057c1 [AA] Make ModRefInfo a bitmask enum (NFC)
Mark ModRefInfo as a bitmask enum, which allows using normal
& and | operators on it. This supersedes various functions like
unionModRef() and intersectModRef(). I think this makes the code
cleaner than going through helper functions...

Differential Revision: https://reviews.llvm.org/D130870
2022-08-03 10:05:55 +02:00
Nikita Popov dcf4b733ef [SCEVExpander] Make CanonicalMode handing in isSafeToExpand() more robust (PR50506)
isSafeToExpand() for addrecs depends on whether the SCEVExpander
will be used in CanonicalMode. At least one caller currently gets
this wrong, resulting in PR50506.

Fix this by a) making the CanonicalMode argument on the freestanding
functions required and b) adding member functions on SCEVExpander
that automatically take the SCEVExpander mode into account. We can
use the latter variant nearly everywhere, and thus make sure that
there is no chance of CanonicalMode mismatch.

Fixes https://github.com/llvm/llvm-project/issues/50506.

Differential Revision: https://reviews.llvm.org/D129630
2022-07-14 14:41:51 +02:00
Kazu Hirata 611ffcf4e4 [llvm] Use value instead of getValue (NFC) 2022-07-13 23:11:56 -07:00
Nuno Lopes 53dc0f1078 [NFC] Switch a few uses of undef to poison as placeholders for unreachble code 2022-07-03 14:34:03 +01:00
Kazu Hirata a7938c74f1 [llvm] Don't use Optional::hasValue (NFC)
This patch replaces Optional::hasValue with the implicit cast to bool
in conditionals only.
2022-06-25 21:42:52 -07:00
Kazu Hirata 3b7c3a654c Revert "Don't use Optional::hasValue (NFC)"
This reverts commit aa8feeefd3.
2022-06-25 11:56:50 -07:00
Kazu Hirata aa8feeefd3 Don't use Optional::hasValue (NFC) 2022-06-25 11:55:57 -07:00
Guillaume Chatelet dc9c2eac98 [NFC][Alignment] Simplify code 2022-06-10 15:25:28 +00:00
Eli Friedman abdf0da800 [LoopIdiom] Fix bailout for aliasing in memcpy transform.
Commit dd5991cc modified the aliasing checks here to allow transforming
a memcpy where the source and destination point into the same object.
However, the change accidentally made the code skip the alias check for
other operations in the loop.

Instead of completely skipping the alias check, just skip the check for
whether the memcpy aliases itself.

Differential Revision: https://reviews.llvm.org/D126486
2022-05-31 17:24:23 -07:00
Jonas Paulsson 304378fd09 Reapply "[BuildLibCalls] Introduce getOrInsertLibFunc() for use when building
libcalls." (was 0f8c626). This reverts commit 14d9390.

The patch previously failed to recognize cases where user had defined a
function alias with an identical name as that of the library
function. Module::getFunction() would then return nullptr which is what the
sanitizer discovered.

In this updated version a new function isLibFuncEmittable() has as well been
introduced which is now used instead of TLI->has() anytime a library function
is to be emitted . It additionally also makes sure there is e.g. no function
alias with the same name in the module.

Reviewed By: Eli Friedman

Differential Revision: https://reviews.llvm.org/D123198
2022-05-02 19:37:00 +02:00
David Green 9727c77d58 [NFC] Rename Instrinsic to Intrinsic 2022-04-25 18:13:23 +01:00
Fangrui Song 14d9390721 Revert D123198 "[BuildLibCalls] Introduce getOrInsertLibFunc() for use when building libcalls."
test/Transforms/InstCombine/pr39177.ll failed in a -DLLVM_USE_SANITIZER=Undefined build.
```
lib/Transforms/Utils/BuildLibCalls.cpp:1217:17: runtime error: reference binding to null pointer of type 'llvm::Function'
```
`Function &F = *M->getFunction(Name);`

This reverts commit 0f8c626723.
2022-04-19 22:26:10 -07:00
Jonas Paulsson 0f8c626723 [BuildLibCalls] Introduce getOrInsertLibFunc() for use when building libcalls.
A new set of overloaded functions named getOrInsertLibFunc() are now supposed
to be used instead of getOrInsertFunction() when building a libcall from
within an LLVM optimizer(). The idea is that this new function also makes
sure that any mandatory argument attributes are added to the function
prototype (after calling getOrInsertFunction()).

inferLibFuncAttributes() is renamed to inferNonMandatoryLibFuncAttrs() as it
only adds attributes that are not necessary for correctness but merely
helping with later optimizations.

Generally, the front end is responsible for building a correct function
prototype with the needed argument attributes. If the middle end however is
the one creating the call, e.g. when replacing one libcall with another, it
then must take this responsibility.

This continues the work of properly handling argument extension if required
by the target ABI when building a lib call. getOrInsertLibFunc() now does
this for all libcalls currently built by any LLVM optimizer. It is expected
that when in the future a new optimization builds a new libcall with an
integer argument it is to be added to getOrInsertLibFunc() with the proper
handling. Note that not all targets have it in their ABI to sign/zero extend
integer arguments to the full register width, but this will be done
selectively as determined by getExtAttrForI32Param().

Review: Eli Friedman, Nikita Popov, Dávid Bolvanský

Differential Revision: https://reviews.llvm.org/D123198
2022-04-19 21:22:07 +02:00
Stephen Long e02f4976ac [LoopIdiom] Merge TBAA of adjacent stores when creating memset
Factor in the TBAA of adjacent stores instead of just the head store
when merging stores into a memset. We were seeing GVN remove a load that
had a TBAA that matched the 2nd store because GVN determined it didn't
match the TBAA of the memset. The memset had the TBAA of only the first
store.

i.e. Loading the field pi_ of shared_count after memset to create an
array of shared_ptr

template<class T>
class shared_ptr {
  T *p;
  shared_count refcount;
};

class shared_count {
  sp_counted_base *pi_;
};

Differential Revision: https://reviews.llvm.org/D122205
2022-03-30 16:54:49 -07:00
serge-sans-paille 59630917d6 Cleanup includes: Transform/Scalar
Estimated impact on preprocessor output line:
before: 1062981579
after:  1062494547

Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup
Differential Revision: https://reviews.llvm.org/D120817
2022-03-03 07:56:34 +01:00
Kazu Hirata befeb5acf6 [Transforms] Use default member initialization in MemmoveVerifier (NFC) 2022-02-13 10:34:03 -08:00
William S. Moses 8cb9c73609 [LoopIdiom] Keep TBAA when creating memcpy/memmove
When upgrading a loop of load/store to a memcpy, the existing pass does not keep existing aliasing information. This patch allows existing aliasing information to be kept.

Reviewed By: jeroen.dobbelaere

Differential Revision: https://reviews.llvm.org/D108221
2022-01-31 16:28:13 -05:00
Florian Hahn 1ce01b7dfe
[SCEVExpander] Simplify cleanup, skip sorting by dominance.
There is no need to sort inserted instructions by dominance, as the
deletion loop still requires RAUW with undef before deleting. Removing
instructions in reverse insertion order should still insure that the
number of uselist updates is kept to a minimum.
2022-01-09 18:38:41 +00:00
eopXD ecb3ae524e [LoopIdiom] Use utility from SE instead of local rewriter
ScalarEvolution::applyLoopGuards shall do the work.

Reviewed By: reames

Differential Revision: https://reviews.llvm.org/D115784
2021-12-15 20:46:49 -08:00
Arthur Eubanks 5a81a60391 [NFC] Remove more calls to getAlignment()
These are deprecated and should be replaced with getAlign().

Some of these asserts don't do anything because Load/Store/AllocaInst never have a 0 align value.
2021-12-15 14:40:57 -08:00
eopXD bc17d32a5f [LoopIdiom] Let LIR fold memset pointer / stride SCEV regarding loop guards
Expression guraded in loop entry can be folded prior to comparison. This patch
proceeds D107353 and makes LIR able to deal with nested for-loop.

Reviewed By: qianzhen, bmahjour

Differential Revision: https://reviews.llvm.org/D108112
2021-12-13 09:36:58 -08:00
Kazu Hirata c714da2ceb [Transforms] Use {DenseSet,SetVector,SmallPtrSet}::contains (NFC) 2021-10-31 07:57:32 -07:00
Dawid Jurczak 9ba5bb4309 [NFC][LoopIdiom] Make for loops more readable
Patch simplifies for loops in LIR following LLVM guidelines: https://llvm.org/docs/CodingStandards.html#use-range-based-for-loops-wherever-possible.

Differential Revision: https://reviews.llvm.org/D112077
2021-10-21 12:17:44 +02:00
Clement Courbet 6aaf1e7ea9 [LoopIdiom] Fix store size SCEV type.
We were using the type of the loop back edge count to represent the
store size. This failed for small loop counts (e.g. in the added test,
the loop count was an i2).

Use the index type instead.

Fixes PR52104.

Differential Revision: https://reviews.llvm.org/D111401
2021-10-11 09:39:06 +02:00
Dawid Jurczak dd5991cc6f [LoopIdiom] Transform loop containing memcpy to memmove
The purpose of patch is to learn Loop Idiom Recognize pass how to recognize simple memmove patterns
in similar way like GCC does: https://godbolt.org/z/dKjGvTGff
It's follow-up of following change: https://reviews.llvm.org/D104464

Differential Revision: https://reviews.llvm.org/D107075
2021-10-08 09:56:01 +02:00
Jon Roelofs 4b19e7dfae [LoopIdiomRecognize][Remarks] Track loop-strided store to/from blocks
Differential revision: https://reviews.llvm.org/D109929
2021-09-16 15:46:26 -07:00
Dawid Jurczak bdcf04246c [LoopIdiom] Don't transform loop into memmove when load from body has more than one use
This change fixes issue found by Markus: https://reviews.llvm.org/rG11338e998df1
Before this patch following code was transformed to memmove:

for (int i = 15; i >= 1; i--) {
  p[i] = p[i-1];
  sum += p[i-1];
}

However load from p[i-1] is used not only by store to p[i] but also by sum computation.
Therefore we cannot emit memmove in loop header.

Differential Revision: https://reviews.llvm.org/D107964
2021-08-25 14:22:40 +02:00
eopXD 4fc98ca617 [NFC][LoopIdiom] Let processLoopStoreOfLoopLoad take StoreSize as SCEV instead of unsigned
Letting it take SCEV allows further modification on the function to optimize
if the StoreSize / Stride is runtime determined.

The plan is to let memcpy / memmove deal with runtime-determined sizes, just
like what D107353 did to memset.

Reviewed By: bmahjour

Differential Revision: https://reviews.llvm.org/D108289
2021-08-21 00:03:28 -07:00
Han Zhu 687f046c97 [NFC][loop-idiom] Rename Stores to IgnoredInsts; Fix a typo
When dealing with memmove, we also add the load instruction to the ignored
instructions list passed to `mayLoopAccessLocation`. Renaming "Stores" to
"IgnoredInsts" to be more precise.

Differential Revision: https://reviews.llvm.org/D108275
2021-08-18 10:52:16 -07:00
eopXD 012173680f [LoopIdiom] let the pass deal with runtime memset size
The current LIR does not deal with runtime-determined memset-size. This patch
utilizes SCEV and check if the PointerStrideSCEV and the MemsetSizeSCEV are equal.
Before comparison the pass would try to fold the expression that is already
protected by the loop guard.

Testcase file `memset-runtime.ll`, `memset-runtime-debug.ll` added.

This patch deals with proper loop-idiom. Proceeding patch wants to deal with SCEV-s
that are inequal after folding with the loop guards.

Reviewed By: lebedev.ri, Whitney

Differential Revision: https://reviews.llvm.org/D107353
2021-08-14 19:22:06 +08:00
eopXD fd7f6a3c81 [NFC][LoopIdiom] rename boolean variable NegStride to IsNegStride
Rename variable for better code readability.

Reviewed By: lebedev.ri

Differential Revision: https://reviews.llvm.org/D107570
2021-08-05 23:11:42 +08:00
eopXD 26aa1bbe97 [NFCI] [LoopIdiom] Let processLoopStridedStore take StoreSize as SCEV instead of unsigned
Letting it take SCEV allows further modification on the function to optimize
if the StoreSize / Stride is runtime determined.

This is a preceeding of D107353.
The big picture is to let LoopIdiom deal with runtime-determined sizes.

Reviewed By: Whitney, lebedev.ri

Differential Revision: https://reviews.llvm.org/D104595
2021-08-05 13:21:48 +08:00
Dawid Jurczak 11338e998d [LoopIdiom] Transform memmove-like loop into memmove (PR46179)
The purpose of patch is to learn Loop idiom recognition pass how to recognize simple memmove patterns
in similar way like GCC: https://godbolt.org/z/fh95e83od
LoopIdiomRecognize already has machinery for memset and memcpy recognition, patch tries to extend exisiting capabilities with minimal effort.

Differential Revision: https://reviews.llvm.org/D104464
2021-07-22 13:05:43 +02:00
Jon Roelofs 37b6e03c18 [Intrinsics] Make MemCpyInlineInst a MemCpyInst
This opens up more optimization opportunities in passes that already handle MemCpyInst's.

Differential revision: https://reviews.llvm.org/D105247
2021-07-02 10:25:24 -07:00
Philip Reames 7629b2a09c [LI] Add a cover function for checking if a loop is mustprogress [nfc]
Essentially, the cover function simply combines the loop level check and the function level scope into one call.  This simplifies several callers and is (subjectively) less error prone.
2021-06-10 13:37:32 -07:00
Roman Lebedev 149e018d12
[LoopIdiom] 'arithmetic right-shift until zero': don't turn potentially infinite loops into finite ones
Nowadays LLVM does not assume that all loops are finite,
so if we want to produce a finite loop from a potentially-infinite one,
we must ensure that the original loop is known to be a finite one.

For this transform, it only matters for arithmetic right-shifts.
For them, either the function or the loop must be known to
be `mustprogress`, or the original value being shifted must be known
to be non-negative (because iff the sign bit was set,
it will never become zero, but will become `-1` in the "end").

It would be really good for alive2 to actually complain about this,
but it currently does not: https://github.com/AliveToolkit/alive2/issues/726
2021-05-25 21:02:28 +03:00
Roman Lebedev 8f4db14d1c
[LoopIdiom] Support 'left-shift until zero' idiom
This adds support for the "count active bits" pattern, i.e.:
```
int countBits(unsigned val) {
    int cnt = 0;
    for( ; (val << cnt) != 0; ++cnt)
        ;
    return cnt;
}
```
but a somewhat more general one:
```
int countBits(unsigned val, int start, int off) {
    int cnt;
    for (cnt = start; val << (cnt + off); cnt++)
        ;
    return cnt;
}
```

alive2 is happy with all the tests there.

Note that, again, much like with the right-shift cases,
we don't require the `val != 0` guard.

This is the last pattern that was supported by
`detectShiftUntilZeroIdiom()`, which now becomes obsolete.
2021-05-25 15:26:35 +03:00
Roman Lebedev f1c5f78d38
[LoopIdiom] Support 'arithmetic right-shift until zero' idiom
This adds support for the "count active bits" pattern, i.e.:
```
int countActiveBits(signed val) {
    int cnt = 0;
    for( ; (val >> cnt) != 0; ++cnt)
        ;
    return cnt;
}
```
but a somewhat more general one:
```
int countActiveBits(signed val, int start, int off) {
    int cnt;
    for (cnt = start; val >> (cnt + off); cnt++)
        ;
    return cnt;
}
```

This directly matches the existing 'logical right-shift until zero' idiom.
alive2 is happy with all the tests there.

Note that, again, much like with the original unsigned case,
we don't require the `val != 0` guard.

The old `detectShiftUntilZeroIdiom()` already supports this pattern,
the idea here is that the `val` must be positive (have at least one
leading zero), because otherwise the loop is non-terminating,
but since it is not `while(1)`, that would have been UB.
2021-05-25 14:30:49 +03:00
Roman Lebedev 32bee42719
[NFCI][LoopIdiom] 'left-shift until bittest': assert that BaseX is loop-invariant
Given that BaseX is an incoming value when coming from the preheader,
it *should* be loop-invariant, but let's just document this assumption.
2021-05-24 12:15:06 +03:00
Roman Lebedev aa3dac95ed
[LoopIdiom] 'logical right shift until zero': the value must be loop-invariant
As per the reproducer provided by Mikael Holmén in post-commit review.
2021-05-24 12:15:06 +03:00
Roman Lebedev 0633d5ce7b
[LoopIdiom] 'logical right-shift until zero' ('count active bits') "on steroids" idiom recognition.
I think i've added exhaustive test coverage, and i have verified that alive2 is happy with all the tests,
so in principle i'm fine with landing this without review, but just in case..

This adds support for the "count active bits" pattern, i.e.:
```
int countActiveBits(unsigned val) {
    int cnt = 0;
    for( ; (val >> cnt) != 0; ++cnt)
        ;
    return cnt;
}
```
but a somewhat more general one, since that is what i need:
```
int countActiveBits(unsigned val, int start, int off) {
    int cnt;
    for (cnt = start; val >> (cnt + off); cnt++)
        ;
    return cnt;
}
```

I've followed in footstep of 'left-shift until bittest' idiom (D91038),
in the sense that iff the `ctlz` intrinsic is cheap, we'll transform,
regardless of all other factors.

This can have a shocking effect on certain benchmarks:
```
raw.pixls.us-unique/Olympus/XZ-1$ /repositories/googlebenchmark/tools/compare.py -a benchmarks ~/rawspeed/build-{old,new}/src/utilities/rsbench/rsbench --benchmark_counters_tabular=true --benchmark_min_time=0.00000001 --benchmark_repetitions=128 p1319978.orf
RUNNING: /home/lebedevri/rawspeed/build-old/src/utilities/rsbench/rsbench --benchmark_counters_tabular=true --benchmark_min_time=0.00000001 --benchmark_repetitions=128 p1319978.orf --benchmark_display_aggregates_only=true --benchmark_out=/tmp/tmp49_28zcm
2021-05-09T01:06:05+03:00
Running /home/lebedevri/rawspeed/build-old/src/utilities/rsbench/rsbench
Run on (32 X 3600.24 MHz CPU s)
CPU Caches:
  L1 Data 32 KiB (x16)
  L1 Instruction 32 KiB (x16)
  L2 Unified 512 KiB (x16)
  L3 Unified 32768 KiB (x2)
Load Average: 5.26, 6.29, 3.49
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Benchmark                                                      Time             CPU   Iterations  CPUTime,s CPUTime/WallTime     Pixels Pixels/CPUTime Pixels/WallTime Raws/CPUTime Raws/WallTime WallTime,s
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
p1319978.orf/threads:32/process_time/real_time_mean          145 ms          145 ms          128   0.145319         0.999981   10.1568M       69.8949M        69.8936M      6.88159       6.88146   0.145322
p1319978.orf/threads:32/process_time/real_time_median        145 ms          145 ms          128   0.145317         0.999986   10.1568M       69.8941M        69.8931M      6.88151       6.88141   0.145319
p1319978.orf/threads:32/process_time/real_time_stddev      0.766 ms        0.766 ms          128   766.586u         15.1302u          0       354.167k        354.098k    0.0348699     0.0348631   766.469u
RUNNING: /home/lebedevri/rawspeed/build-new/src/utilities/rsbench/rsbench --benchmark_counters_tabular=true --benchmark_min_time=0.00000001 --benchmark_repetitions=128 p1319978.orf --benchmark_display_aggregates_only=true --benchmark_out=/tmp/tmpwb9sw2x0
2021-05-09T01:06:24+03:00
Running /home/lebedevri/rawspeed/build-new/src/utilities/rsbench/rsbench
Run on (32 X 3599.95 MHz CPU s)
CPU Caches:
  L1 Data 32 KiB (x16)
  L1 Instruction 32 KiB (x16)
  L2 Unified 512 KiB (x16)
  L3 Unified 32768 KiB (x2)
Load Average: 4.05, 5.95, 3.43
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Benchmark                                                      Time             CPU   Iterations  CPUTime,s CPUTime/WallTime     Pixels Pixels/CPUTime Pixels/WallTime Raws/CPUTime Raws/WallTime WallTime,s
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
p1319978.orf/threads:32/process_time/real_time_mean         99.8 ms         99.8 ms          128  0.0997758         0.999972   10.1568M       101.797M        101.794M      10.0225       10.0222  0.0997786
p1319978.orf/threads:32/process_time/real_time_median       99.7 ms         99.7 ms          128  0.0997165         0.999985   10.1568M       101.857M        101.854M      10.0284       10.0281  0.0997195
p1319978.orf/threads:32/process_time/real_time_stddev      0.224 ms        0.224 ms          128   224.166u          34.345u          0        226.81k        227.231k    0.0223309     0.0223723   224.586u
Comparing /home/lebedevri/rawspeed/build-old/src/utilities/rsbench/rsbench to /home/lebedevri/rawspeed/build-new/src/utilities/rsbench/rsbench
Benchmark                                                               Time             CPU      Time Old      Time New       CPU Old       CPU New
----------------------------------------------------------------------------------------------------------------------------------------------------
p1319978.orf/threads:32/process_time/real_time_pvalue                 0.0000          0.0000      U Test, Repetitions: 128 vs 128
p1319978.orf/threads:32/process_time/real_time_mean                  -0.3134         -0.3134           145           100           145           100
p1319978.orf/threads:32/process_time/real_time_median                -0.3138         -0.3138           145           100           145           100
p1319978.orf/threads:32/process_time/real_time_stddev                -0.7073         -0.7078             1             0             1             0

```

Reviewed By: craig.topper, zhuhan0

Differential Revision: https://reviews.llvm.org/D102116
2021-05-17 20:33:33 +03:00
Han Zhu da1cdffbb1 [loop-idiom] Hoist loop memcpys to loop preheader
For a simple loop like:
```
struct S {
  int x;
  int y;
  char b;
};

unsigned foo(S* __restrict__ a, S* b, int n) {
  for (int i = 0; i < n; i++)
    a[i] = b[i];

  return sizeof(a[0]);
}
```
We could eliminate the loop and convert it to a large memcpy of 12*n bytes. Currently this is not handled. Output of `opt -loop-idiom -S < memcpy_before.ll`
```
%struct.S = type { i32, i32, i8 }

define dso_local i32 @_Z3fooP1SS0_i(%struct.S* noalias nocapture %a, %struct.S* nocapture readonly %b, i32 %n) local_unnamed_addr {
entry:
  %cmp7 = icmp sgt i32 %n, 0
  br i1 %cmp7, label %for.body.preheader, label %for.cond.cleanup

for.body.preheader:                               ; preds = %entry
  br label %for.body

for.cond.cleanup.loopexit:                        ; preds = %for.body
  br label %for.cond.cleanup

for.cond.cleanup:                                 ; preds = %for.cond.cleanup.loopexit, %entry
  ret i32 12

for.body:                                         ; preds = %for.body, %for.body.preheader
  %i.08 = phi i32 [ %inc, %for.body ], [ 0, %for.body.preheader ]
  %idxprom = zext i32 %i.08 to i64
  %arrayidx = getelementptr inbounds %struct.S, %struct.S* %b, i64 %idxprom
  %arrayidx2 = getelementptr inbounds %struct.S, %struct.S* %a, i64 %idxprom
  %0 = bitcast %struct.S* %arrayidx2 to i8*
  %1 = bitcast %struct.S* %arrayidx to i8*
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* nonnull align 4 dereferenceable(12) %0, i8* nonnull align 4 dereferenceable(12) %1, i64 12, i1 false)
  %inc = add nuw nsw i32 %i.08, 1
  %cmp = icmp slt i32 %inc, %n
  br i1 %cmp, label %for.body, label %for.cond.cleanup.loopexit
}

; Function Attrs: argmemonly nofree nosync nounwind willreturn
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* noalias nocapture writeonly, i8* noalias nocapture readonly, i64, i1 immarg) #0

attributes #0 = { argmemonly nofree nosync nounwind willreturn }

```
The loop idiom pass currently only handles load and store instructions. Since struct S is too big to fit in a register, the loop body contains a memcpy intrinsic.

With this change, re-run `opt -loop-idiom -S < memcpy_before.ll`. The loop memcpy is promoted to loop preheader. For this trivial case, the loop is dead and will be removed by another pass.
```
%struct.S = type { i32, i32, i8 }

define dso_local i32 @_Z3fooP1SS0_i(%struct.S* noalias nocapture %a, %struct.S* nocapture readonly %b, i32 %n) local_unnamed_addr {
entry:
  %a1 = bitcast %struct.S* %a to i8*
  %b2 = bitcast %struct.S* %b to i8*
  %cmp7 = icmp sgt i32 %n, 0
  br i1 %cmp7, label %for.body.preheader, label %for.cond.cleanup

for.body.preheader:                               ; preds = %entry
  %0 = zext i32 %n to i64
  %1 = mul nuw nsw i64 %0, 12
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 4 %a1, i8* align 4 %b2, i64 %1, i1 false)
  br label %for.body

for.cond.cleanup.loopexit:                        ; preds = %for.body
  br label %for.cond.cleanup

for.cond.cleanup:                                 ; preds = %for.cond.cleanup.loopexit, %entry
  ret i32 12

for.body:                                         ; preds = %for.body, %for.body.preheader
  %i.08 = phi i32 [ %inc, %for.body ], [ 0, %for.body.preheader ]
  %idxprom = zext i32 %i.08 to i64
  %arrayidx = getelementptr inbounds %struct.S, %struct.S* %b, i64 %idxprom
  %arrayidx2 = getelementptr inbounds %struct.S, %struct.S* %a, i64 %idxprom
  %2 = bitcast %struct.S* %arrayidx2 to i8*
  %3 = bitcast %struct.S* %arrayidx to i8*
  %inc = add nuw nsw i32 %i.08, 1
  %cmp = icmp slt i32 %inc, %n
  br i1 %cmp, label %for.body, label %for.cond.cleanup.loopexit
}

; Function Attrs: argmemonly nofree nosync nounwind willreturn
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* noalias nocapture writeonly, i8* noalias nocapture readonly, i64, i1 immarg) #0

attributes #0 = { argmemonly nofree nosync nounwind willreturn }
```

Reviewed By: zino

Differential Revision: https://reviews.llvm.org/D97667
2021-05-04 17:05:04 -07:00
Tres Popp efce19c3b0 Revert "[loop-idiom] Hoist loop memcpys to loop preheader"
This reverts commit 75d6b8bb40.

The reasoning is mentioned in https://reviews.llvm.org/D97667
2021-04-28 13:16:34 +02:00
Han Zhu 75d6b8bb40 [loop-idiom] Hoist loop memcpys to loop preheader
For a simple loop like:
```
struct S {
  int x;
  int y;
  char b;
};

unsigned foo(S* __restrict__ a, S* b, int n) {
  for (int i = 0; i < n; i++)
    a[i] = b[i];

  return sizeof(a[0]);
}
```
We could eliminate the loop and convert it to a large memcpy of 12*n bytes. Currently this is not handled. Output of `opt -loop-idiom -S < memcpy_before.ll`
```
%struct.S = type { i32, i32, i8 }

define dso_local i32 @_Z3fooP1SS0_i(%struct.S* noalias nocapture %a, %struct.S* nocapture readonly %b, i32 %n) local_unnamed_addr {
entry:
  %cmp7 = icmp sgt i32 %n, 0
  br i1 %cmp7, label %for.body.preheader, label %for.cond.cleanup

for.body.preheader:                               ; preds = %entry
  br label %for.body

for.cond.cleanup.loopexit:                        ; preds = %for.body
  br label %for.cond.cleanup

for.cond.cleanup:                                 ; preds = %for.cond.cleanup.loopexit, %entry
  ret i32 12

for.body:                                         ; preds = %for.body, %for.body.preheader
  %i.08 = phi i32 [ %inc, %for.body ], [ 0, %for.body.preheader ]
  %idxprom = zext i32 %i.08 to i64
  %arrayidx = getelementptr inbounds %struct.S, %struct.S* %b, i64 %idxprom
  %arrayidx2 = getelementptr inbounds %struct.S, %struct.S* %a, i64 %idxprom
  %0 = bitcast %struct.S* %arrayidx2 to i8*
  %1 = bitcast %struct.S* %arrayidx to i8*
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* nonnull align 4 dereferenceable(12) %0, i8* nonnull align 4 dereferenceable(12) %1, i64 12, i1 false)
  %inc = add nuw nsw i32 %i.08, 1
  %cmp = icmp slt i32 %inc, %n
  br i1 %cmp, label %for.body, label %for.cond.cleanup.loopexit
}

; Function Attrs: argmemonly nofree nosync nounwind willreturn
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* noalias nocapture writeonly, i8* noalias nocapture readonly, i64, i1 immarg) #0

attributes #0 = { argmemonly nofree nosync nounwind willreturn }

```
The loop idiom pass currently only handles load and store instructions. Since struct S is too big to fit in a register, the loop body contains a memcpy intrinsic.

With this change, re-run `opt -loop-idiom -S < memcpy_before.ll`. The loop memcpy is promoted to loop preheader. For this trivial case, the loop is dead and will be removed by another pass.
```
%struct.S = type { i32, i32, i8 }

define dso_local i32 @_Z3fooP1SS0_i(%struct.S* noalias nocapture %a, %struct.S* nocapture readonly %b, i32 %n) local_unnamed_addr {
entry:
  %a1 = bitcast %struct.S* %a to i8*
  %b2 = bitcast %struct.S* %b to i8*
  %cmp7 = icmp sgt i32 %n, 0
  br i1 %cmp7, label %for.body.preheader, label %for.cond.cleanup

for.body.preheader:                               ; preds = %entry
  %0 = zext i32 %n to i64
  %1 = mul nuw nsw i64 %0, 12
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 4 %a1, i8* align 4 %b2, i64 %1, i1 false)
  br label %for.body

for.cond.cleanup.loopexit:                        ; preds = %for.body
  br label %for.cond.cleanup

for.cond.cleanup:                                 ; preds = %for.cond.cleanup.loopexit, %entry
  ret i32 12

for.body:                                         ; preds = %for.body, %for.body.preheader
  %i.08 = phi i32 [ %inc, %for.body ], [ 0, %for.body.preheader ]
  %idxprom = zext i32 %i.08 to i64
  %arrayidx = getelementptr inbounds %struct.S, %struct.S* %b, i64 %idxprom
  %arrayidx2 = getelementptr inbounds %struct.S, %struct.S* %a, i64 %idxprom
  %2 = bitcast %struct.S* %arrayidx2 to i8*
  %3 = bitcast %struct.S* %arrayidx to i8*
  %inc = add nuw nsw i32 %i.08, 1
  %cmp = icmp slt i32 %inc, %n
  br i1 %cmp, label %for.body, label %for.cond.cleanup.loopexit
}

; Function Attrs: argmemonly nofree nosync nounwind willreturn
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* noalias nocapture writeonly, i8* noalias nocapture readonly, i64, i1 immarg) #0

attributes #0 = { argmemonly nofree nosync nounwind willreturn }
```

Reviewed By: zino

Differential Revision: https://reviews.llvm.org/D97667
2021-04-27 17:37:51 -07:00
Han Zhu cd13f19031 [loop-idiom][NFC] Extract processLoopStoreOfLoopLoad into a helper function
Differential Revision: https://reviews.llvm.org/D100979
2021-04-27 13:42:30 -07:00
Vitaly Buka f2a585e6d3 [NFC] Fix "not used" warning 2021-04-26 22:09:23 -07:00
Roman Lebedev 005881e96e
[LoopIdiom] left-shift-until-bittest: set all allowed no-wrap flags on add/sub
I've checked each one of these with alive2,
and this is both correct and precise.
2021-04-11 18:08:07 +03:00
Craig Topper 5fc0e98d9a [LoopIdiomRecognize] Minor cleanups to the FFS idiom matching. NFC
-Make sure of the CreateShl/LShr/AShr methods that take a uint64_t
instead of creating a ConstantInt for 1 ourselves.
-Use Builder.getInt1 or ConstantInt::getBool instead of a conditional.
-Pull out repeated calls to getType.
2021-04-07 10:03:14 -07:00
Krasimir Georgiev 8e7df996e3 Revert "[loop-idiom] Hoist loop memcpys to loop preheader"
This reverts commit 92ddd3c1b6.

Causes multistage clang crashes, e.g.:
https://lab.llvm.org/buildbot/#/builders/36/builds/6678
2021-03-30 11:47:12 +02:00