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Author SHA1 Message Date
Aditya Kumar dfa8741c96 [GVNHoist] Factor out reachability to search for anticipable instructions quickly 
Factor out the reachability such that multiple queries to find reachability of values are fast. This is based on finding
the ANTIC points
in the CFG which do not change during hoisting. The ANTIC points are basically the dominance-frontiers in the inverse
graph. So we introduce a data structure (CHI nodes)
to keep track of values flowing out of a basic block. We only do this for values with multiple occurrences in the
function as they are the potential hoistable candidates.

This patch allows us to hoist instructions to a basic block with >2 successors, as well as deal with infinite loops in a
trivial way.
Relevant test cases are added to show the functionality as well as regression fixes from PR32821.

Regression from previous GVNHoist:
We do not hoist fully redundant expressions because fully redundant expressions are already handled by NewGVN

Differential Revision: https://reviews.llvm.org/D35918
Reviewers: dberlin, sebpop, gberry,

llvm-svn: 313116
 2017-09-13 05:28:03 +00:00
Chandler Carruth c246a4c973 Disable GVN Hoist due to still more bugs being found in it. There is 
also a discussion about exactly what we should do prior to re-enabling
it.

The current bug is http://llvm.org/PR32821 and the discussion about this
is in the review thread for r300200.

llvm-svn: 301505
 2017-04-27 00:28:03 +00:00
Geoff Berry 85a530fb59 Re-apply "[GVNHoist] Move GVNHoist to function simplification part of pipeline." 
This reverts commit r296872 now that PR32153 has been fixed.

llvm-svn: 300200
 2017-04-13 15:36:25 +00:00
Geoff Berry 635e505675 [GVNHoist] Call isGuaranteedToTransferExecutionToSuccessor on each instruction 
w.r.t. https://bugs.llvm.org/show_bug.cgi?id=32153
The consensus seems to be isGuaranteedToTransferExecutionToSuccessor should be called for each function.

Patch by Aditya Kumar

Differential Revision: https://reviews.llvm.org/D31035

llvm-svn: 299882
 2017-04-10 20:45:17 +00:00
Matt Arsenault f10061ec70 Add address space mangling to lifetime intrinsics 
In preparation for allowing allocas to have non-0 addrspace.

llvm-svn: 299876
 2017-04-10 20:18:21 +00:00
Sebastian Pop 4a4d245b19 Handle UnreachableInst in isGuaranteedToTransferExecutionToSuccessor 
A block with an UnreachableInst does not transfer execution to a successor.
The problem was exposed by GVN-hoist. This patch fixes bug 32153.

Patch by Aditya Kumar.

Differential Revision: https://reviews.llvm.org/D30667

llvm-svn: 297254
 2017-03-08 01:54:50 +00:00
Benjamin Kramer 9528f8c2fb Revert "Re-apply "[GVNHoist] Move GVNHoist to function simplification part of pipeline."" 
This reverts commit r296759. Miscompiles bash.

llvm-svn: 296872
 2017-03-03 14:27:53 +00:00
Geoff Berry 484d756583 Re-apply "[GVNHoist] Move GVNHoist to function simplification part of pipeline." 
This re-applies r289696, which caused TSan perf regression, which has
since been addressed in separate changes (see PR for details).

See PR31382.

llvm-svn: 296759
 2017-03-02 16:16:47 +00:00
Hans Wennborg 19c0be90f9 [GVNHoist] Don't hoist unsafe scalars at -Oz (PR31729) 
Based on Aditya Kumar's patch:

Differential Revision: https://reviews.llvm.org/D29092

llvm-svn: 296642
 2017-03-01 17:15:08 +00:00
Reid Kleckner 828f3179c2 Fix my GVNHoist test case from r294317 
llvm-svn: 294319
 2017-02-07 17:35:53 +00:00
Reid Kleckner 79e37d517c Revert "[GVNHoist] Merge DebugLoc metadata on hoisted instructions" 
This reverts commit r294250. It caused PR31891.

Add a test case that shows that inlinable calls retain location
information with an accurate scope.

llvm-svn: 294317
 2017-02-07 17:31:13 +00:00
Taewook Oh 44a856f7d5 [GVNHoist] Merge DebugLoc metadata on hoisted instructions 
Summary:
When instructions are hoisted, current implementation keeps DebugLoc metadata of the instruction that chosen as Repl (and its GEP operand if Repl is a load or a store). However, DebugLoc metadata should be updated to the 'merged' location across all hoisted instructions. See the following example code:


```
  1:  typedef struct {
  2:    int a[10];
  3:  } S1;
  4: 
  5:  extern S1 *s1[10];
  6: 
  7:  void foo(int x, int y, int i) {
  8:    if (y)
  9:      s1[i]->a[i] = x + y;
 10:    else
 11:      s1[i]->a[i] = x;
 12:  }
```

Below is LLVM IR representation of the program before gvn-hoist:


```
%struct.S1 = type { [10 x i32] }
@s1 = external local_unnamed_addr global [10 x %struct.S1*], align 16

define void @foo(i32 %x, i32 %y, i32 %i) !dbg !4 {
entry:
  %tobool = icmp ne i32 %y, 0, !dbg !8
  br i1 %tobool, label %if.then, label %if.else, !dbg !10

if.then:                                          ; preds = %entry
  %add = add nsw i32 %x, %y, !dbg !11
  %idxprom = sext i32 %i to i64, !dbg !12
  %arrayidx = getelementptr inbounds [10 x %struct.S1*], [10 x %struct.S1*]* @s1, i64 0, i64 %idxprom, !dbg !12
  %0 = load %struct.S1*, %struct.S1** %arrayidx, align 8, !dbg !12, !tbaa !13
  %a = getelementptr inbounds %struct.S1, %struct.S1* %0, i32 0, i32 0, !dbg !17
  br label %if.end, !dbg !12

if.else:                                          ; preds = %entry
  %idxprom3 = sext i32 %i to i64, !dbg !18
  %arrayidx4 = getelementptr inbounds [10 x %struct.S1*], [10 x %struct.S1*]* @s1, i64 0, i64 %idxprom3, !dbg !18
  %1 = load %struct.S1*, %struct.S1** %arrayidx4, align 8, !dbg !18, !tbaa !13
  %a5 = getelementptr inbounds %struct.S1, %struct.S1* %1, i32 0, i32 0, !dbg !19
  br label %if.end

if.end:                                           ; preds = %if.else, %if.then
  %a5.sink = phi [10 x i32]* [ %a5, %if.else ], [ %a, %if.then ]
  %.sink = phi i32 [ %x, %if.else ], [ %add, %if.then ]
  %idxprom6 = sext i32 %i to i64
  %arrayidx7 = getelementptr inbounds [10 x i32], [10 x i32]* %a5.sink, i64 0, i64 %idxprom6
  store i32 %.sink, i32* %arrayidx7, align 4, !tbaa !20
  ret void, !dbg !22
}

```
where


```
!11 = !DILocation(line: 9, column: 18, scope: !9)
!12 = !DILocation(line: 9, column: 5, scope: !9)
!18 = !DILocation(line: 11, column: 5, scope: !9)
!19 = !DILocation(line: 11, column: 9, scope: !9)
```

. And below is after gvn-hoist:


```
define void @foo(i32 %x, i32 %y, i32 %i) !dbg !4 {
entry:
  %tobool = icmp ne i32 %y, 0, !dbg !8
  %idxprom = sext i32 %i to i64, !dbg !10
  %0 = getelementptr inbounds [10 x %struct.S1*], [10 x %struct.S1*]* @s1, i64 0, i64 %idxprom, !dbg !10
  %1 = load %struct.S1*, %struct.S1** %0, align 8, !dbg !10, !tbaa !11
  br i1 %tobool, label %if.then, label %if.else, !dbg !15

if.then:                                          ; preds = %entry
  %add = add nsw i32 %x, %y, !dbg !16
  %arrayidx = getelementptr inbounds [10 x %struct.S1*], [10 x %struct.S1*]* @s1, i64 0, i64 %idxprom, !dbg !10
  %a = getelementptr inbounds %struct.S1, %struct.S1* %1, i32 0, i32 0, !dbg !17
  br label %if.end, !dbg !10

if.else:                                          ; preds = %entry
  %arrayidx4 = getelementptr inbounds [10 x %struct.S1*], [10 x %struct.S1*]* @s1, i64 0, i64 %idxprom, !dbg !18
  %a5 = getelementptr inbounds %struct.S1, %struct.S1* %1, i32 0, i32 0, !dbg !19
  br label %if.end

if.end:                                           ; preds = %if.else, %if.then
  %a5.sink = phi [10 x i32]* [ %a5, %if.else ], [ %a, %if.then ]
  %.sink = phi i32 [ %x, %if.else ], [ %add, %if.then ]
  %arrayidx7 = getelementptr inbounds [10 x i32], [10 x i32]* %a5.sink, i64 0, i64 %idxprom
  store i32 %.sink, i32* %arrayidx7, align 4, !tbaa !20
  ret void, !dbg !22
}

```
As you see, loads and their GEPs have been hosited from if.then/if.else block to entry block. However, DebugLoc metadata of these new instructions are still same as the instructions in if.then block, as they are moved/cloned from if.then block. This may result incorrect stepping and imprecise sample profile result.

Reviewers: majnemer, pcc, sebpop

Reviewed By: sebpop

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D29377

llvm-svn: 294250
 2017-02-06 22:05:04 +00:00
Daniel Berlin 390dfde0f3 Remove the load hoisting code of MLSM, it is completely subsumed by GVNHoist 
Summary:
GVNHoist performs all the optimizations that MLSM does to loads, in a
more general way, and in a faster time bound (MLSM is N^3 in most
cases, N^4 in a few edge cases).

This disables the load portion.

Note that the way ld_hoist_st_sink.ll is written makes one think that
the loads should be moved to the while.preheader block, but

1. Neither MLSM nor GVNHoist do it (they both move them to identical places).

2. MLSM couldn't possibly do it anyway, as the while.preheader block
is not the head of the diamond, while.body is.  (GVNHoist could do it
if it was legal).

3. At a glance, it's not legal anyway because the in-loop load
conflict with the in-loop store, so the loads must stay in-loop.

I am happy to update the test to use update_test_checks so that
checking is tighter, just was going to do it as a followup.

Note that i can find no particular benefit to the store portion on any
real testcase/benchmark i have (even size-wise).  If we really still
want it, i am happy to commit to writing a targeted store sinker, just
taking the code from the MemorySSA port of MergedLoadStoreMotion
(which is N^2 worst case, and N most of the time).

We can do what it does in a much better time bound.

We also should be both hoisting and sinking stores, not just sinking
them, anyway, since whether we should hoist or sink to merge depends
basically on luck of the draw of where the blockers are placed.

Nonetheless, i have left it alone for now.

Reviewers: chandlerc, davide

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D29079

llvm-svn: 292971
 2017-01-24 19:55:36 +00:00
Evgeniy Stepanov 95294127d0 Revert "[GVNHoist] Move GVNHoist to function simplification part of pipeline." 
This reverts r289696, which caused TSan perf regression.

See PR31382.

llvm-svn: 290030
 2016-12-17 01:53:15 +00:00
Geoff Berry ca11a1e147 [GVNHoist] Move GVNHoist to function simplification part of pipeline. 
Summary:
Move GVNHoist to later in the optimization pipeline, specifically, to
the function simplification part of the pipeline.  The new pipeline
location allows GVNHoist to run on a function after its callees have
been inlined but before the function has been considered for inlining
into its callers, exposing more opportunities for hoisting.

Performance results on AArch64 kryo:
Improvements:
  Benchmarks/CoyoteBench/fftbench  -24.952%
  spec2006/bzip2                    -4.071%
  internal bmark                    -3.177%
  Benchmarks/PAQ8p/paq8p            -1.754%
  spec2000/perlbmk                  -1.328%
  spec2006/h264ref                  -1.140%

Regressions:
  internal bmark                    +1.818%
  Benchmarks/mafft/pairlocalalign   +1.084%

Reviewers: sebpop, dberlin, hiraditya

Subscribers: aemerson, mehdi_amini, mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D27722

llvm-svn: 289696
 2016-12-14 19:38:22 +00:00
Eli Friedman c6885fc369 [GVNHoist] Invalidate MemDep when an instruction is moved. 
See also r279907.

Fixes https://llvm.org/bugs/show_bug.cgi?id=30991 .

Differential Revision: https://reviews.llvm.org/D27493

llvm-svn: 288968
 2016-12-07 19:55:59 +00:00
Sebastian Pop 5ba9f24ed7 commit back "GVN-hoist: fix store past load dependence analysis (PR30216, PR30499)" 
This is with an extra change to avoid calling MemoryLocation::get() on a call instruction.

Differential Revision: https://reviews.llvm.org/D25542

llvm-svn: 284098
 2016-10-13 01:39:10 +00:00
Reid Kleckner 8958f6a529 Revert "GVN-hoist: fix store past load dependence analysis (PR30216, PR30499)" 
This CL didn't actually address the test case in PR30499, and clang
still crashes.

Also revert dependent change "Memory-SSA cleanup of clobbers interface, NFC"

Reverts r283965 and r283967.

llvm-svn: 284093
 2016-10-13 00:18:26 +00:00
Sebastian Pop ab12fb62ee GVN-hoist: fix store past load dependence analysis (PR30216, PR30499) 
This is a refreshed version of a patch that was reverted: it fixes
the problems reported in both PR30216 and PR30499, and
contains all the test-cases from both bugs.

To hoist stores past loads, we used to search for potential
conflicting loads on the hoisting path by following a MemorySSA
def-def link from the store to be hoisted to the previous
defining memory access, and from there we followed the def-use
chains to all the uses that occur on the hoisting path. The
problem is that the def-def link may point to a store that does
not alias with the store to be hoisted, and so the loads that are
walked may not alias with the store to be hoisted, and even as in
the testcase of PR30216, the loads that may alias with the store
to be hoisted are not visited.

The current patch visits all loads on the path from the store to
be hoisted to the hoisting position and uses the alias analysis
to ask whether the store may alias the load. I was not able to
use the MemorySSA functionality to ask for whether load and
store are clobbered: I'm not sure which function to call, so I
used a call to AA->isNoAlias().

Store past store is still working as before using a MemorySSA
query: I added an extra test to pr30216.ll to make sure store
past store does not regress.

Tested on x86_64-linux with check and a test-suite run.

Differential Revision: https://reviews.llvm.org/D25476

llvm-svn: 283965
 2016-10-12 02:23:39 +00:00
Hans Wennborg c7957ef86c Revert r282168 "GVN-hoist: fix store past load dependence analysis (PR30216)" 
and also the dependent r282175 "GVN-hoist: do not dereference null pointers"

It's causing compiler crashes building Harfbuzz (PR30499).

llvm-svn: 282199
 2016-09-22 21:20:53 +00:00
Sebastian Pop 8e6e3318c2 GVN-hoist: fix store past load dependence analysis (PR30216) 
To hoist stores past loads, we used to search for potential
conflicting loads on the hoisting path by following a MemorySSA
def-def link from the store to be hoisted to the previous
defining memory access, and from there we followed the def-use
chains to all the uses that occur on the hoisting path. The
problem is that the def-def link may point to a store that does
not alias with the store to be hoisted, and so the loads that are
walked may not alias with the store to be hoisted, and even as in
the testcase of PR30216, the loads that may alias with the store
to be hoisted are not visited.

The current patch visits all loads on the path from the store to
be hoisted to the hoisting position and uses the alias analysis
to ask whether the store may alias the load. I was not able to
use the MemorySSA functionality to ask for whether load and
store are clobbered: I'm not sure which function to call, so I
used a call to AA->isNoAlias().

Store past store is still working as before using a MemorySSA
query: I added an extra test to pr30216.ll to make sure store
past store does not regress.

Differential Revision: https://reviews.llvm.org/D24517

llvm-svn: 282168
 2016-09-22 15:33:51 +00:00
Sebastian Pop f6bfc1ad8b GVN-hoist: move hoist testcase to GVNHoist dir 
llvm-svn: 282161
 2016-09-22 14:45:46 +00:00
Sebastian Pop 440f15b7fc GVN-hoist: only hoist relevant scalar instructions 
Without this patch, GVN-hoist would think that a branch instruction is a scalar instruction
and would try to value number it. The patch filters out all such kind of irrelevant instructions.

A bit frustrating is that there is no easy way to discard all those very infrequent instructions,
a bit like isa<TerminatorInst> that stands for a large family of instructions. I'm thinking that
checking for those very infrequent other instructions would cost us more in compilation time
than just letting those instructions getting numbered, so I'm still thinking that a simpler check:

  if (isa<TerminatorInst>(I))
    return false;

is better than listing all the other less frequent instructions.

Differential Revision: https://reviews.llvm.org/D23929

llvm-svn: 282160
 2016-09-22 14:45:40 +00:00
Sebastian Pop 5f0d0e60d1 GVN-hoist: fix hoistingFromAllPaths for loops (PR29034) 
It is invalid to hoist stores or loads if they are not executed on all paths
from the hoisting point to the exit of the function. In the testcase, there are
paths in the loop that do not execute the stores or the loads, and so hoisting
them within the loop is unsafe.

The problem is that the current implementation of hoistingFromAllPaths is
incomplete: it walks all blocks dominated by the hoisting point, and does not
return false when the loop contains a path on which the hoisted ld/st is
not executed.

Differential Revision: https://reviews.llvm.org/D23843

llvm-svn: 279732
 2016-08-25 11:55:47 +00:00
Daniel Berlin 2698cbb4f1 Move GVNHoist tests into their own directory since it is a separate pass 
llvm-svn: 278404
 2016-08-11 20:35:07 +00:00