Lay out trellis-shaped CFGs optimally.
A trellis of the shape below:
A B
|\ /|
| \ / |
| X |
| / \ |
|/ \|
C D
would be laid out A; B->C ; D by the current layout algorithm. Now we identify
trellises and lay them out either A->C; B->D or A->D; B->C. This scales with an
increasing number of predecessors. A trellis is a a group of 2 or more
predecessor blocks that all have the same successors.
because of this we can tail duplicate to extend existing trellises.
As an example consider the following CFG:
B D F H
/ \ / \ / \ / \
A---C---E---G---Ret
Where A,C,E,G are all small (Currently 2 instructions).
The CFG preserving layout is then A,B,C,D,E,F,G,H,Ret.
The current code will copy C into B, E into D and G into F and yield the layout
A,C,B(C),E,D(E),F(G),G,H,ret
define void @straight_test(i32 %tag) {
entry:
br label %test1
test1: ; A
%tagbit1 = and i32 %tag, 1
%tagbit1eq0 = icmp eq i32 %tagbit1, 0
br i1 %tagbit1eq0, label %test2, label %optional1
optional1: ; B
call void @a()
br label %test2
test2: ; C
%tagbit2 = and i32 %tag, 2
%tagbit2eq0 = icmp eq i32 %tagbit2, 0
br i1 %tagbit2eq0, label %test3, label %optional2
optional2: ; D
call void @b()
br label %test3
test3: ; E
%tagbit3 = and i32 %tag, 4
%tagbit3eq0 = icmp eq i32 %tagbit3, 0
br i1 %tagbit3eq0, label %test4, label %optional3
optional3: ; F
call void @c()
br label %test4
test4: ; G
%tagbit4 = and i32 %tag, 8
%tagbit4eq0 = icmp eq i32 %tagbit4, 0
br i1 %tagbit4eq0, label %exit, label %optional4
optional4: ; H
call void @d()
br label %exit
exit:
ret void
}
here is the layout after D27742:
straight_test: # @straight_test
; ... Prologue elided
; BB#0: # %entry ; A (merged with test1)
; ... More prologue elided
mr 30, 3
andi. 3, 30, 1
bc 12, 1, .LBB0_2
; BB#1: # %test2 ; C
rlwinm. 3, 30, 0, 30, 30
beq 0, .LBB0_3
b .LBB0_4
.LBB0_2: # %optional1 ; B (copy of C)
bl a
nop
rlwinm. 3, 30, 0, 30, 30
bne 0, .LBB0_4
.LBB0_3: # %test3 ; E
rlwinm. 3, 30, 0, 29, 29
beq 0, .LBB0_5
b .LBB0_6
.LBB0_4: # %optional2 ; D (copy of E)
bl b
nop
rlwinm. 3, 30, 0, 29, 29
bne 0, .LBB0_6
.LBB0_5: # %test4 ; G
rlwinm. 3, 30, 0, 28, 28
beq 0, .LBB0_8
b .LBB0_7
.LBB0_6: # %optional3 ; F (copy of G)
bl c
nop
rlwinm. 3, 30, 0, 28, 28
beq 0, .LBB0_8
.LBB0_7: # %optional4 ; H
bl d
nop
.LBB0_8: # %exit ; Ret
ld 30, 96(1) # 8-byte Folded Reload
addi 1, 1, 112
ld 0, 16(1)
mtlr 0
blr
The tail-duplication has produced some benefit, but it has also produced a
trellis which is not laid out optimally. With this patch, we improve the layouts
of such trellises, and decrease the cost calculation for tail-duplication
accordingly.
This patch produces the layout A,C,E,G,B,D,F,H,Ret. This layout does have
back edges, which is a negative, but it has a bigger compensating
positive, which is that it handles the case where there are long strings
of skipped blocks much better than the original layout. Both layouts
handle runs of executed blocks equally well. Branch prediction also
improves if there is any correlation between subsequent optional blocks.
Here is the resulting concrete layout:
straight_test: # @straight_test
; BB#0: # %entry ; A (merged with test1)
mr 30, 3
andi. 3, 30, 1
bc 12, 1, .LBB0_4
; BB#1: # %test2 ; C
rlwinm. 3, 30, 0, 30, 30
bne 0, .LBB0_5
.LBB0_2: # %test3 ; E
rlwinm. 3, 30, 0, 29, 29
bne 0, .LBB0_6
.LBB0_3: # %test4 ; G
rlwinm. 3, 30, 0, 28, 28
bne 0, .LBB0_7
b .LBB0_8
.LBB0_4: # %optional1 ; B (Copy of C)
bl a
nop
rlwinm. 3, 30, 0, 30, 30
beq 0, .LBB0_2
.LBB0_5: # %optional2 ; D (Copy of E)
bl b
nop
rlwinm. 3, 30, 0, 29, 29
beq 0, .LBB0_3
.LBB0_6: # %optional3 ; F (Copy of G)
bl c
nop
rlwinm. 3, 30, 0, 28, 28
beq 0, .LBB0_8
.LBB0_7: # %optional4 ; H
bl d
nop
.LBB0_8: # %exit
Differential Revision: https://reviews.llvm.org/D28522
llvm-svn: 295223
We currently can't legalize those, but we should really not be creating
them in the first place, since legalization would probably look similar to the
way we legalize CONCAT_VECTORS - basically replace the INSERT with a BUILD.
This fixes PR311956.
Differential Revision: https://reviews.llvm.org/D29961
llvm-svn: 295213
Summary:
The current code loops over all elements to calculate a used range. Then a second short loop looks at the ranges and determines if they can be used in a extract and creates a properly aligned start index for the extract.
This range finding is unnecessary, we can just calculate a properly aligned start index for an extract for each input during the first loop. If we don't find the same start index for each indice we can't use an extract.
Reviewers: zvi, RKSimon
Reviewed By: zvi
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D29926
llvm-svn: 295152
Summary:
Blocks ending in unreachable are typically cold because they end the
program or throw an exception, so merging them with other identical
blocks is usually profitable because it reduces the size of cold code.
MachineBlockPlacement generally does not arrange to fall through to such
blocks, so commoning these blocks will not introduce additional
unconditional branches.
Reviewers: hans, iteratee, haicheng
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D29153
llvm-svn: 295105
This instruction clears the low bits of a pointer without requiring (possibly
dodgy if pointers aren't ints) conversions to and from an integer. Since (as
far as I'm aware) all masks are statically known, the instruction takes an
immediate operand rather than a register to specify the mask.
llvm-svn: 295103
Store instructions can have more than one memory operand as a result
of optimizations that fold different stores into one.
When we identify spill instructions to generate DBG_VALUE instructions
to record the spilling of a variable, we disregard stores with
multiple memory operands for now. We may miss some relevant spills but
the handling is a bit more complex, so we'll do it in a different patch.
This fixes PR31935.
llvm-svn: 295093
To help assist in debugging ISEL or to prioritize GlobalISel backend
work, this patch adds two more tables to <Target>GenISelDAGISel.inc -
one which contains the patterns that are used during selection and the
other containing include source location of the patterns
Enabled through CMake varialbe LLVM_ENABLE_DAGISEL_COV
llvm-svn: 295081
And use it in MachineOptimizationRemarkEmitter. A test will follow on top of
Justin's changes to enable MachineORE in AsmPrinter.
The approach is similar to the IR-level pass. It's a bit simpler because BPI
is immutable at the Machine level so we don't need to make that lazy.
Because of this, a new function mapping is introduced (BPIPassTrait::getBPI).
This function extracts BPI from the pass. In case of the lazy pass, this is
when the calculation of the BFI occurs. For Machine-level, this is the
identity function.
Differential Revision: https://reviews.llvm.org/D29836
llvm-svn: 295072
Backends don't support this yet. They would have to move to the swifterror
register before the tail call to make sure it is live-in to the call.
rdar://30495920
llvm-svn: 294982
This is consistent with what we do for GlobalISel. That way, it is easy
to see whether or not FastISel is able to fully select a function.
At some point we may want to switch that to an optimization remark.
llvm-svn: 294970
Summary:
Keep a vector of LocInfos around; one for each call to EmitInlineAsm.
Since each call to EmitInlineAsm creates a new buffer in the inline asm
SourceMgr, we can use the buffer number to map to the right LocInfo.
Reviewers: rengolin, grosbach, rnk, echristo
Reviewed By: rnk
Subscribers: mehdi_amini, llvm-commits
Differential Revision: https://reviews.llvm.org/D29769
llvm-svn: 294947
Before this patch compile time was about 21s (see below). After this patch
we have less than 2s (see bellow).
Intel(R) Xeon(R) CPU E5-2676 v3 @ 2.40GHz
DAGCombiner - trunk
time ./llc spill_fdiv.ll -o /dev/null -enable-unsafe-fp-math
real 0m1.685s
DAGCombiner + Speed patch
time ./llc spill_fdiv.ll -o /dev/null -enable-unsafe-fp-math
real 0m1.655s
MachineCombiner w/o Speed patch
time ./llc spill_fdiv.ll -o /dev/null -enable-unsafe-fp-math
real 0m21.614s
MachineCombiner + Speed patch
time ./llc spill_fdiv.ll -o /dev/null -enable-unsafe-fp-math
real 0m1.593s
The test spill_fdiv.ll is attached to D29627
D29627 should be closed.
llvm-svn: 294936
The bug was introduced with:
https://reviews.llvm.org/rL294863
...and manifests as a selection failure in x86, but that's actually
another bug. This fix prevents wrong codegen with -0.0, but in the
more common case when we have NSZ and NNAN (-ffast-math), we should
still be able to fold this setcc/compare.
llvm-svn: 294924
I don't know if anything other than x86 vectors is affected by this change, but this may allow
us to remove target-specific intrinsics for blendv* (vector selects). The simplification arises
from the fact that blendv* instructions only use the sign-bit when deciding which vector element
to choose for the destination vector. The mechanism to fold VSELECT into SHRUNKBLEND nodes already
exists in x86 lowering; this demanded bits change just enables the transform to fire more often.
The original motivation starts with a bug for DSE of masked stores that seems completely unrelated,
but I've explained the likely steps in this series here:
https://llvm.org/bugs/show_bug.cgi?id=11210
Differential Revision: https://reviews.llvm.org/D29687
llvm-svn: 294863
Summary:
powerpc64 big-endian is not supported, but I believe that most logic can
be shared, except for xray_powerpc64.cc.
Also add a function InvalidateInstructionCache to xray_util.h, which is
copied from llvm/Support/Memory.cpp. I'm not sure if I need to add a unittest,
and I don't know how.
Reviewers: dberris, echristo, iteratee, kbarton, hfinkel
Subscribers: mehdi_amini, nemanjai, mgorny, llvm-commits
Differential Revision: https://reviews.llvm.org/D29742
llvm-svn: 294781
The patch comes in 2 parts:
1 - it makes use of the SelectionDAG::NewNodesMustHaveLegalTypes flag to tell when it can safely constant fold illegal types.
2 - it correctly resets SelectionDAG::NewNodesMustHaveLegalTypes at the start of each call to SelectionDAGISel::CodeGenAndEmitDAG so all the pre-legalization stages can make use of it - not just the first basic block that gets handled.
Fix for PR30760
Differential Revision: https://reviews.llvm.org/D29568
llvm-svn: 294749
Summary:
With -debug, we aren't dumping the DAG after legalizing vector ops. In particular, on X86 with AVX1 only, we don't dump the DAG after we split 256-bit integer ops into pairs of 128-bit ADDs since this occurs during vector legalization.
I'm only dumping if the legalize vector ops changes something since we don't print anything during legalize vector ops. So this dump shows up right after the first type-legalization dump happens. So if nothing changed this second dump is unnecessary.
Having said that though, I think we should probably fix legalize vector ops to log what its doing.
Reviewers: RKSimon, eli.friedman, spatel, arsenm, chandlerc
Reviewed By: RKSimon
Subscribers: wdng, llvm-commits
Differential Revision: https://reviews.llvm.org/D29554
llvm-svn: 294711
LLVM defines `PTHREAD_LIB` which is used by AddLLVM.cmake and various projects
to correctly link the threading library when needed. Unfortunately
`PTHREAD_LIB` is defined by LLVM's `config-ix.cmake` file which isn't installed
and therefore can't be used when configuring out-of-tree builds. This causes
such builds to fail since `pthread` isn't being correctly linked.
This patch attempts to fix that problem by renaming and exporting
`LLVM_PTHREAD_LIB` as part of`LLVMConfig.cmake`. I renamed `PTHREAD_LIB`
because It seemed likely to cause collisions with downstream users of
`LLVMConfig.cmake`.
llvm-svn: 294690
Summary:
Fix two bugs in SelectionDAGBuilder::FindMergedConditions reported by
Mikael Holmen. Handle non-canonicalized xor not operation
correctly (was assuming operand 0 was always the non-constant operand)
and check that the negated condition is also in the same block as the
original and/or instruction (as is done for and/or operands already)
before proceeding with optimization.
Reviewers: bogner, MatzeB, qcolombet
Subscribers: mcrosier, uabelho, llvm-commits
Differential Revision: https://reviews.llvm.org/D29680
llvm-svn: 294605
Stack Smash Protection is not completely free, so in hot code, the overhead it causes can cause performance issues. By adding diagnostic information for which function have SSP and why, a user can quickly determine what they can do to stop SSP being applied to a specific hot function.
This change adds an SSP-specific DiagnosticInfo class and uses of it to the Stack Protection code. A subsequent change to clang will cause the remarks to be emitted when enabled.
Patch by: James Henderson
Differential Revision: https://reviews.llvm.org/D29023
llvm-svn: 294590
It'll usually be immediately legalized back to a libcall, but occasionally
something can be done with it so we'd just as well enable that flexibility from
the start.
llvm-svn: 294530
AArch64 has specific instructions to multiply two numbers at double the width
and produce the high part of the result. These can be used to implement LLVM's
mul.with.overflow instructions fairly simply. Helps with C++ operator new[].
llvm-svn: 294519
Fixed test.
Summary:
Enables source location in diagnostic messages from the backend. This
is after parsing, during finalization. This requires the SourceMgr, the
inline assembly string buffer, and DiagInfo to still be alive after
EmitInlineAsm returns.
This patch creates a single SourceMgr for inline assembly inside the
AsmPrinter. MCContext gets a pointer to this SourceMgr. Using one
SourceMgr per call to EmitInlineAsm would make it difficult for
MCContext to figure out in which SourceMgr the SMLoc is located, while a
single SourceMgr can figure it out if it has multiple buffers.
The Str argument to EmitInlineAsm is copied into a buffer and owned by
the inline asm SourceMgr. This ensures that DiagHandlers won't print
garbage. (Clang emits a "note: instantiated into assembly here", which
refers to this string.)
The AsmParser gets destroyed before finalization, which means that the
DiagHandlers the AsmParser installs into the SourceMgr will be stale.
Restore the saved DiagHandlers.
Since now we're using just one SourceMgr for multiple inline asm
strings, we need to tell the AsmParser which buffer it needs to parse
currently. Hand a buffer id -- returned from SourceMgr::
AddNewSourceBuffer -- to the AsmParser.
Reviewers: rnk, grosbach, compnerd, rengolin, rovka, anemet
Reviewed By: rnk
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D29441
llvm-svn: 294458
It caused undefined behavior in VarLoc. As far as I investigated,
- VarLoc::VarLoc() treats negative offset value as InvalidKind.
Consider the case that (int64_t)MI.getOperand(1).getImm() is negative and whether it satisfies ((uint64_t)Offset < (1ULL << 32)).
- Comparison operators in VarLoc behave undefined since VarLoc::Loc.Hash is uninitialized in case of InvalidKind.
I guess Offset (in VarLoc) could be made aware of signed, but I am not sure.
So I have reverted it for now.
llvm-svn: 294447
Summary:
Enables source location in diagnostic messages from the backend. This
is after parsing, during finalization. This requires the SourceMgr, the
inline assembly string buffer, and DiagInfo to still be alive after
EmitInlineAsm returns.
This patch creates a single SourceMgr for inline assembly inside the
AsmPrinter. MCContext gets a pointer to this SourceMgr. Using one
SourceMgr per call to EmitInlineAsm would make it difficult for
MCContext to figure out in which SourceMgr the SMLoc is located, while a
single SourceMgr can figure it out if it has multiple buffers.
The Str argument to EmitInlineAsm is copied into a buffer and owned by
the inline asm SourceMgr. This ensures that DiagHandlers won't print
garbage. (Clang emits a "note: instantiated into assembly here", which
refers to this string.)
The AsmParser gets destroyed before finalization, which means that the
DiagHandlers the AsmParser installs into the SourceMgr will be stale.
Restore the saved DiagHandlers.
Since now we're using just one SourceMgr for multiple inline asm
strings, we need to tell the AsmParser which buffer it needs to parse
currently. Hand a buffer id -- returned from SourceMgr::
AddNewSourceBuffer -- to the AsmParser.
Reviewers: rnk, grosbach, compnerd, rengolin, rovka, anemet
Reviewed By: rnk
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D29441
llvm-svn: 294433
