This makes it possible for targets to define their own MCObjectFileInfo.
This MCObjectFileInfo is then used to determine things like section alignment.
This is a follow up to D101462 and prepares for the RISCV backend defining the
text section alignment depending on the enabled extensions.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D101921
This untangles the MCContext and the MCObjectFileInfo. There is a circular
dependency between MCContext and MCObjectFileInfo. Currently this dependency
also exists during construction: You can't contruct a MOFI without a MCContext
without constructing the MCContext with a dummy version of that MOFI first.
This removes this dependency during construction. In a perfect world,
MCObjectFileInfo wouldn't depend on MCContext at all, but only be stored in the
MCContext, like other MC information. This is future work.
This also shifts/adds more information to the MCContext making it more
available to the different targets. Namely:
- TargetTriple
- ObjectFileType
- SubtargetInfo
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D101462
This changes adds attribute field for metadata of context profile. Currently we have an inline attribute that indicates whether the leaf frame corresponding to a context profile was inlined in previous build.
This will be used to help estimating inlining and be taken into account when trimming context. Changes for that in llvm-profgen will follow. It will also help tuning.
Differential Revision: https://reviews.llvm.org/D98823
Previously we didn't support to keep the unique linkage name(-funique-internal-linkage-name) in llvm-profgen. As discussed in https://reviews.llvm.org/D96932, we choose to do canonicalization for it.
Now since "selected" is set as the default parameter of getCanonicalFnName in `D96932`, we don't need to add any attribute here for the previous usage and only fix the missing usage in the pseudo probe decoding.
Differential Revision: https://reviews.llvm.org/D98226
Previously we errored out when disassembling illegal instructions and there would be no profile generated. In fact illegal instructions are not uncommon and we'd better skip them and print "unknown" instead of erroring out. This matches the behavior of llvm-objdump (see disassembleObject in llvm-objdump.cpp).
Reviewed By: wlei, wenlei
Differential Revision: https://reviews.llvm.org/D97776
It appears some instructions doesn't have the debug location info and the symbolizer will return an empty call stack for them which will cause some crash later in profile unwinding. Actually we do not record the sample info for them, so this change just filter out those instruction.
As those instruction would appears at the begin and end of the instruction list, without them we need to add the boundary check for IP `advance` and `backward`.
Also for pseudo probe based profile, we actually don't need the symbolized location info, so here just change to use an empty stack for it. This could save half of the binary loading time.
Differential Revision: https://reviews.llvm.org/D96434
This include some changes related with PerfReader's the input check and command line change:
1) It appears there might be thousands of leading MMAP-Event line in the perfscript for large workload. For this case, the 4k threshold is not eligible to determine it's a hybrid sample. This change renovated the `isHybridPerfScript` by going through the script without threshold limitation checking whether there is a non-empty call stack immediately followed by a LBR sample. It will stop once it find a valid one.
2) Added several input validations for the command line switches in PerfReader.
3) Changed the command line `show-disassembly` to `show-disassembly-only`, it will print to stdout and exit early which leave an empty output profile.
Reviewed By: hoy, wenlei
Differential Revision: https://reviews.llvm.org/D96387
To align with https://reviews.llvm.org/D95547, we need to add brackets for context id before initializing the `SampleContext`.
Also added test cases for extended binary format from llvm-profgen side.
Differential Revision: https://reviews.llvm.org/D95929
For CS profile generation, the process of call stack unwinding is time-consuming since for each LBR entry we need linear time to generate the context( hash, compression, string concatenation). This change speeds up this by grouping all the call frame within one LBR sample into a trie and aggregating the result(sample counter) on it, deferring the context compression and string generation to the end of unwinding.
Specifically, it uses `StackLeaf` as the top frame on the stack and manipulates(pop or push a trie node) it dynamically during virtual unwinding so that the raw sample can just be recoded on the leaf node, the path(root to leaf) will represent its calling context. In the end, it traverses the trie and generates the context on the fly.
Results:
Our internal branch shows about 5X speed-up on some large workloads in SPEC06 benchmark.
Differential Revision: https://reviews.llvm.org/D94110
This change compresses the context string by removing cycles due to recursive function for CS profile generation. Removing recursion cycles is a way to normalize the calling context which will be better for the sample aggregation and also make the context promoting deterministic.
Specifically for implementation, we recognize adjacent repeated frames as cycles and deduplicated them through multiple round of iteration.
For example:
Considering a input context string stack:
[“a”, “a”, “b”, “c”, “a”, “b”, “c”, “b”, “c”, “d”]
For first iteration,, it removed all adjacent repeated frames of size 1:
[“a”, “b”, “c”, “a”, “b”, “c”, “b”, “c”, “d”]
For second iteration, it removed all adjacent repeated frames of size 2:
[“a”, “b”, “c”, “a”, “b”, “c”, “d”]
So in the end, we get compressed output:
[“a”, “b”, “c”, “d”]
Compression will be called in two place: one for sample's context key right after unwinding, one is for the eventual context string id in the ProfileGenerator.
Added a switch `compress-recursion` to control the size of duplicated frames, default -1 means no size limit.
Added unit tests and regression test for this.
Differential Revision: https://reviews.llvm.org/D93556
For CS profile generation, the process of call stack unwinding is time-consuming since for each LBR entry we need linear time to generate the context( hash, compression, string concatenation). This change speeds up this by grouping all the call frame within one LBR sample into a trie and aggregating the result(sample counter) on it, deferring the context compression and string generation to the end of unwinding.
Specifically, it uses `StackLeaf` as the top frame on the stack and manipulates(pop or push a trie node) it dynamically during virtual unwinding so that the raw sample can just be recoded on the leaf node, the path(root to leaf) will represent its calling context. In the end, it traverses the trie and generates the context on the fly.
Results:
Our internal branch shows about 5X speed-up on some large workloads in SPEC06 benchmark.
Differential Revision: https://reviews.llvm.org/D94110
This change compresses the context string by removing cycles due to recursive function for CS profile generation. Removing recursion cycles is a way to normalize the calling context which will be better for the sample aggregation and also make the context promoting deterministic.
Specifically for implementation, we recognize adjacent repeated frames as cycles and deduplicated them through multiple round of iteration.
For example:
Considering a input context string stack:
[“a”, “a”, “b”, “c”, “a”, “b”, “c”, “b”, “c”, “d”]
For first iteration,, it removed all adjacent repeated frames of size 1:
[“a”, “b”, “c”, “a”, “b”, “c”, “b”, “c”, “d”]
For second iteration, it removed all adjacent repeated frames of size 2:
[“a”, “b”, “c”, “a”, “b”, “c”, “d”]
So in the end, we get compressed output:
[“a”, “b”, “c”, “d”]
Compression will be called in two place: one for sample's context key right after unwinding, one is for the eventual context string id in the ProfileGenerator.
Added a switch `compress-recursion` to control the size of duplicated frames, default -1 means no size limit.
Added unit tests and regression test for this.
Differential Revision: https://reviews.llvm.org/D93556
This change extends virtual unwinder to support pseudo probe in llvm-profgen. Please refer https://groups.google.com/g/llvm-dev/c/1p1rdYbL93s and https://reviews.llvm.org/D89707 for more context about CSSPGO and llvm-profgen.
**Implementation**
- Added `ProbeBasedCtxKey` derived from `ContextKey` for sample counter aggregation. As we need string splitting to infer the profile for callee function, string based context introduces more string handling overhead, here we just use probe pointer based context.
- For linear unwinding, as inline context is encoded in each pseudo probe, we don't need to go through each instruction to extract range sharing same inliner. So just record the range for the context.
- For probe based context, we should ignore the top frame probe since it will be extracted from the address range. we defer the extraction in `ProfileGeneration`.
- Added `PseudoProbeProfileGenerator` for pseudo probe based profile generation.
- Some helper function to get pseduo probe info(call probe, inline context) from profiled binary.
- Added regression test for unwinder's output
The pseudo probe based profile generation will be in the upcoming patch.
Test Plan:
ninja & ninja check-llvm
Differential Revision: https://reviews.llvm.org/D92896
This change implements pseudo probe decoding and disassembling for llvm-profgen/CSSPGO. Please see https://groups.google.com/g/llvm-dev/c/1p1rdYbL93s and https://reviews.llvm.org/D89707 for more context about CSSPGO and llvm-profgen.
**ELF section format**
Please see the encoding patch(https://reviews.llvm.org/D91878) for more details of the format, just copy the example here:
Two section(`.pseudo_probe_desc` and `.pseudoprobe` ) is emitted in ELF to support pseudo probe.
The format of `.pseudo_probe_desc` section looks like:
```
.section .pseudo_probe_desc,"",@progbits
.quad 6309742469962978389 // Func GUID
.quad 4294967295 // Func Hash
.byte 9 // Length of func name
.ascii "_Z5funcAi" // Func name
.quad 7102633082150537521
.quad 138828622701
.byte 12
.ascii "_Z8funcLeafi"
.quad 446061515086924981
.quad 4294967295
.byte 9
.ascii "_Z5funcBi"
.quad -2016976694713209516
.quad 72617220756
.byte 7
.ascii "_Z3fibi"
```
For each `.pseudoprobe` section, the encoded binary data consists of a single function record corresponding to an outlined function (i.e, a function with a code entry in the `.text` section). A function record has the following format :
```
FUNCTION BODY (one for each outlined function present in the text section)
GUID (uint64)
GUID of the function
NPROBES (ULEB128)
Number of probes originating from this function.
NUM_INLINED_FUNCTIONS (ULEB128)
Number of callees inlined into this function, aka number of
first-level inlinees
PROBE RECORDS
A list of NPROBES entries. Each entry contains:
INDEX (ULEB128)
TYPE (uint4)
0 - block probe, 1 - indirect call, 2 - direct call
ATTRIBUTE (uint3)
reserved
ADDRESS_TYPE (uint1)
0 - code address, 1 - address delta
CODE_ADDRESS (uint64 or ULEB128)
code address or address delta, depending on ADDRESS_TYPE
INLINED FUNCTION RECORDS
A list of NUM_INLINED_FUNCTIONS entries describing each of the inlined
callees. Each record contains:
INLINE SITE
GUID of the inlinee (uint64)
ID of the callsite probe (ULEB128)
FUNCTION BODY
A FUNCTION BODY entry describing the inlined function.
```
**Disassembling**
A switch `--show-pseudo-probe` is added to use along with `--show-disassembly` to print disassembly code with pseudo probe directives.
For example:
```
00000000002011a0 <foo2>:
2011a0: 50 push rax
2011a1: 85 ff test edi,edi
[Probe]: FUNC: foo2 Index: 1 Type: Block
2011a3: 74 02 je 2011a7 <foo2+0x7>
[Probe]: FUNC: foo2 Index: 3 Type: Block
[Probe]: FUNC: foo2 Index: 4 Type: Block
[Probe]: FUNC: foo Index: 1 Type: Block Inlined: @ foo2:6
2011a5: 58 pop rax
2011a6: c3 ret
[Probe]: FUNC: foo2 Index: 2 Type: Block
2011a7: bf 01 00 00 00 mov edi,0x1
[Probe]: FUNC: foo2 Index: 5 Type: IndirectCall
2011ac: ff d6 call rsi
[Probe]: FUNC: foo2 Index: 4 Type: Block
2011ae: 58 pop rax
2011af: c3 ret
```
**Implementation**
- `PseudoProbeDecoder` is added in ProfiledBinary as an infra for the decoding. It decoded the two section and generate two map: `GUIDProbeFunctionMap` stores all the `PseudoProbeFunction` which is the abstraction of a general function. `AddressProbesMap` stores all the pseudo probe info indexed by its address.
- All the inline info is encoded into binary as a trie(`PseudoProbeInlineTree`) and will be constructed from the decoding. Each pseudo probe can get its inline context(`getInlineContext`) by traversing its inline tree node backwards.
Test Plan:
ninja & ninja check-llvm
Differential Revision: https://reviews.llvm.org/D92334
This stack of changes introduces `llvm-profgen` utility which generates a profile data file from given perf script data files for sample-based PGO. It’s part of(not only) the CSSPGO work. Specifically to support context-sensitive with/without pseudo probe profile, it implements a series of functionalities including perf trace parsing, instruction symbolization, LBR stack/call frame stack unwinding, pseudo probe decoding, etc. Also high throughput is achieved by multiple levels of sample aggregation and compatible format with one stop is generated at the end. Please refer to: https://groups.google.com/g/llvm-dev/c/1p1rdYbL93s for the CSSPGO RFC.
This change supports context-sensitive profile data generation into llvm-profgen. With simultaneous sampling for LBR and call stack, we can identify leaf of LBR sample with calling context from stack sample . During the process of deriving fall through path from LBR entries, we unwind LBR by replaying all the calls and returns (including implicit calls/returns due to inlining) backwards on top of the sampled call stack. Then the state of call stack as we unwind through LBR always represents the calling context of current fall through path.
we have two types of virtual unwinding 1) LBR unwinding and 2) linear range unwinding.
Specifically, for each LBR entry which can be classified into call, return, regular branch, LBR unwinding will replay the operation by pushing, popping or switching leaf frame towards the call stack and since the initial call stack is most recently sampled, the replay should be in anti-execution order, i.e. for the regular case, pop the call stack when LBR is call, push frame on call stack when LBR is return. After each LBR processed, it also needs to align with the next LBR by going through instructions from previous LBR's target to current LBR's source, which we named linear unwinding. As instruction from linear range can come from different function by inlining, linear unwinding will do the range splitting and record counters through the range with same inline context.
With each fall through path from LBR unwinding, we aggregate each sample into counters by the calling context and eventually generate full context sensitive profile (without relying on inlining) to driver compiler's PGO/FDO.
A breakdown of noteworthy changes:
- Added `HybridSample` class as the abstraction perf sample including LBR stack and call stack
* Extended `PerfReader` to implement auto-detect whether input perf script output contains CS profile, then do the parsing. Multiple `HybridSample` are extracted
* Speed up by aggregating `HybridSample` into `AggregatedSamples`
* Added VirtualUnwinder that consumes aggregated `HybridSample` and implements unwinding of calls, returns, and linear path that contains implicit call/return from inlining. Ranges and branches counters are aggregated by the calling context. Here calling context is string type, each context is a pair of function name and callsite location info, the whole context is like `main:1 @ foo:2 @ bar`.
* Added PorfileGenerater that accumulates counters by ranges unfolding or branch target mapping, then generates context-sensitive function profile including function body, inferring callee's head sample, callsite target samples, eventually records into ProfileMap.
* Leveraged LLVM build-in(`SampleProfWriter`) writer to support different serialization format with no stop
- `getCanonicalFnName` for callee name and name from ELF section
- Added regression test for both unwinding and profile generation
Test Plan:
ninja & ninja check-llvm
Reviewed By: hoy, wenlei, wmi
Differential Revision: https://reviews.llvm.org/D89723
This stack of changes introduces `llvm-profgen` utility which generates a profile data file from given perf script data files for sample-based PGO. It’s part of(not only) the CSSPGO work. Specifically to support context-sensitive with/without pseudo probe profile, it implements a series of functionalities including perf trace parsing, instruction symbolization, LBR stack/call frame stack unwinding, pseudo probe decoding, etc. Also high throughput is achieved by multiple levels of sample aggregation and compatible format with one stop is generated at the end. Please refer to: https://groups.google.com/g/llvm-dev/c/1p1rdYbL93s for the CSSPGO RFC.
This change adds the support of instruction symbolization. Given the RVA on an instruction pointer, a full calling context can be printed side-by-side with the disassembly code.
E.g.
```
Disassembly of section .text [0x0, 0x4a]:
<funcA>:
0: mov eax, edi funcA:0
2: mov ecx, dword ptr [rip] funcLeaf:2 @ funcA:1
8: lea edx, [rcx + 3] fib:2 @ funcLeaf:2 @ funcA:1
b: cmp ecx, 3 fib:2 @ funcLeaf:2 @ funcA:1
e: cmovl edx, ecx fib:2 @ funcLeaf:2 @ funcA:1
11: sub eax, edx funcLeaf:2 @ funcA:1
13: ret funcA:2
14: nop word ptr cs:[rax + rax]
1e: nop
<funcLeaf>:
20: mov eax, edi funcLeaf:1
22: mov ecx, dword ptr [rip] funcLeaf:2
28: lea edx, [rcx + 3] fib:2 @ funcLeaf:2
2b: cmp ecx, 3 fib:2 @ funcLeaf:2
2e: cmovl edx, ecx fib:2 @ funcLeaf:2
31: sub eax, edx funcLeaf:2
33: ret funcLeaf:3
34: nop word ptr cs:[rax + rax]
3e: nop
<fib>:
40: lea eax, [rdi + 3] fib:2
43: cmp edi, 3 fib:2
46: cmovl eax, edi fib:2
49: ret fib:8
```
Test Plan:
ninja check-llvm
Reviewed By: wenlei, wmi
Differential Revision: https://reviews.llvm.org/D89715
This stack of changes introduces `llvm-profgen` utility which generates a profile data file from given perf script data files for sample-based PGO. It’s part of(not only) the CSSPGO work. Specifically to support context-sensitive with/without pseudo probe profile, it implements a series of functionalities including perf trace parsing, instruction symbolization, LBR stack/call frame stack unwinding, pseudo probe decoding, etc. Also high throughput is achieved by multiple levels of sample aggregation and compatible format with one stop is generated at the end. Please refer to: https://groups.google.com/g/llvm-dev/c/1p1rdYbL93s for the CSSPGO RFC.
This change enables disassembling the text sections to build various address maps that are potentially used by the virtual unwinder. A switch `--show-disassembly` is being added to print the disassembly code.
Like the llvm-objdump tool, this change leverages existing LLVM components to parse and disassemble ELF binary files. So far X86 is supported.
Test Plan:
ninja check-llvm
Reviewed By: wmi, wenlei
Differential Revision: https://reviews.llvm.org/D89712
Philipp Krones