3d6841b2b1
Let Propeller use specialized IDs for basic blocks, instead of MBB number.
This allows optimizations not just prior to asm-printer, but throughout the entire codegen.
This patch only implements the functionality under the new `LLVM_BB_ADDR_MAP` version, but the old version is still being used. A later patch will change the used version.
####Background
Today Propeller uses machine basic block (MBB) numbers, which already exist, to map native assembly to machine IR. This is done as follows.
- Basic block addresses are captured and dumped into the `LLVM_BB_ADDR_MAP` section just before the AsmPrinter pass which writes out object files. This ensures that we have a mapping that is close to assembly.
- Profiling mapping works by taking a virtual address of an instruction and looking up the `LLVM_BB_ADDR_MAP` section to find the MBB number it corresponds to.
- While this works well today, we need to do better when we scale Propeller to target other Machine IR optimizations like spill code optimization. Register allocation happens earlier in the Machine IR pipeline and we need an annotation mechanism that is valid at that point.
- The current scheme will not work in this scenario because the MBB number of a particular basic block is not fixed and changes over the course of codegen (via renumbering, adding, and removing the basic blocks).
- In other words, the volatile MBB numbers do not provide a one-to-one correspondence throughout the lifetime of Machine IR. Profile annotation using MBB numbers is restricted to a fixed point; only valid at the exact point where it was dumped.
- Further, the object file can only be dumped before AsmPrinter and cannot be dumped at an arbitrary point in the Machine IR pass pipeline. Hence, MBB numbers are not suitable and we need something else.
####Solution
We propose using fixed unique incremental MBB IDs for basic blocks instead of volatile MBB numbers. These IDs are assigned upon the creation of machine basic blocks. We modify `MachineFunction::CreateMachineBasicBlock` to assign the fixed ID to every newly created basic block. It assigns `MachineFunction::NextMBBID` to the MBB ID and then increments it, which ensures having unique IDs.
To ensure correct profile attribution, multiple equivalent compilations must generate the same Propeller IDs. This is guaranteed as long as the MachineFunction passes run in the same order. Since the `NextBBID` variable is scoped to `MachineFunction`, interleaving of codegen for different functions won't cause any inconsistencies.
The new encoding is generated under the new version number 2 and we keep backward-compatibility with older versions.
####Impact on Size of the `LLVM_BB_ADDR_MAP` Section
Emitting the Propeller ID results in a 23% increase in the size of the `LLVM_BB_ADDR_MAP` section for the clang binary.
Reviewed By: tmsriram
Differential Revision: https://reviews.llvm.org/D100808
258 lines
7.9 KiB
Plaintext
258 lines
7.9 KiB
Plaintext
## This test checks how we handle the --bb-addr-map option.
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## Fails on windows (https://github.com/llvm/llvm-project/issues/60013).
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# UNSUPPORTED: system-windows
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## Check 64-bit:
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# RUN: yaml2obj --docnum=1 %s -DBITS=64 -DADDR=0x999999999 -o %t1.x64.o
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# RUN: llvm-readobj %t1.x64.o --bb-addr-map 2>&1 | FileCheck %s -DADDR=0x999999999 -DFILE=%t1.x64.o --check-prefix=CHECK
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# RUN: llvm-readelf %t1.x64.o --bb-addr-map | FileCheck %s --check-prefix=GNU
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## Check 64-bit:
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# RUN: yaml2obj --docnum=1 %s -DBITS=64 -DADDR=0x999999999 -o %t1.v1.x64.o
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# RUN: llvm-readobj %t1.v1.x64.o --bb-addr-map 2>&1 | FileCheck %s -DADDR=0x999999999 -DFILE=%t1.v1.x64.o --check-prefix=CHECK
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## Check 32-bit:
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# RUN: yaml2obj --docnum=1 %s -DBITS=32 -o %t1.x32.o
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# RUN: llvm-readobj %t1.x32.o --bb-addr-map 2>&1 | FileCheck -DADDR=0x11111 %s -DFILE=%t1.x32.o --check-prefix=CHECK
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# RUN: llvm-readelf %t1.x32.o --bb-addr-map | FileCheck %s --check-prefix=GNU
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## Check that a malformed section can be handled.
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# RUN: yaml2obj --docnum=1 %s -DBITS=32 -DSIZE=6 -o %t2.o
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# RUN: llvm-readobj %t2.o --bb-addr-map 2>&1 | FileCheck %s -DOFFSET=0x00000006 -DFILE=%t2.o --check-prefix=TRUNCATED
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# CHECK: BBAddrMap [
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# CHECK-NEXT: Function {
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# CHECK-NEXT: At: [[ADDR]]
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# CHECK-NEXT: warning: '[[FILE]]': could not identify function symbol for address ([[ADDR]]) in SHT_LLVM_BB_ADDR_MAP section with index 3
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# CHECK-NEXT: Name: <?>
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# CHECK-NEXT: BB entries [
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# CHECK-NEXT: {
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# CHECK-NEXT: ID: 0
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# CHECK-NEXT: Offset: 0x0
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# CHECK-NEXT: Size: 0x1
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# CHECK-NEXT: HasReturn: No
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# CHECK-NEXT: HasTailCall: Yes
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# CHECK-NEXT: IsEHPad: No
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# CHECK-NEXT: CanFallThrough: No
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# CHECK-NEXT: }
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# CHECK-NEXT: {
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# CHECK-NEXT: ID: 2
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# CHECK-NEXT: Offset: 0x4
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# CHECK-NEXT: Size: 0x4
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# CHECK-NEXT: HasReturn: Yes
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# CHECK-NEXT: HasTailCall: No
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# CHECK-NEXT: IsEHPad: Yes
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# CHECK-NEXT: CanFallThrough: No
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# CHECK-NEXT: }
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# CHECK-NEXT: ]
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# CHECK-NEXT: }
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# CHECK-NEXT: Function {
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# CHECK-NEXT: At: 0x22222
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# CHECK-NEXT: Name: foo
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# CHECK-NEXT: BB entries [
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# CHECK-NEXT: {
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# CHECK-NEXT: ID: 4
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# CHECK-NEXT: Offset: 0x6
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# CHECK-NEXT: Size: 0x7
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# CHECK-NEXT: HasReturn: No
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# CHECK-NEXT: HasTailCall: No
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# CHECK-NEXT: IsEHPad: No
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# CHECK-NEXT: CanFallThrough: Yes
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# CHECK-NEXT: }
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# CHECK-NEXT: ]
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# CHECK-NEXT: }
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# CHECK-NEXT: ]
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# GNU: GNUStyle::printBBAddrMaps not implemented
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# TRUNCATED: BBAddrMap [
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# TRUNCATED-NEXT: warning: '[[FILE]]': unable to dump SHT_LLVM_BB_ADDR_MAP section with index 3: unable to decode LEB128 at offset [[OFFSET]]: malformed uleb128, extends past end
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# TRUNCATED-NEXT: ]
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## Check that the other valid section is properly dumped.
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# TRUNCATED-NEXT: BBAddrMap [
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# TRUNCATED-NEXT: Function {
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# TRUNCATED-NEXT: At: 0x33333
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# TRUNCATED-NEXT: Name: bar
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# TRUNCATED-NEXT: BB entries [
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# TRUNCATED-NEXT: {
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# TRUNCATED-NEXT: ID: 6
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# TRUNCATED-NEXT: Offset: 0x9
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# TRUNCATED-NEXT: Size: 0xA
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# TRUNCATED-NEXT: HasReturn: Yes
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# TRUNCATED-NEXT: HasTailCall: Yes
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# TRUNCATED-NEXT: IsEHPad: No
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# TRUNCATED-NEXT: CanFallThrough: Yes
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# TRUNCATED-NEXT: }
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# TRUNCATED-NEXT: {
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# TRUNCATED-NEXT: ID: 7
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# TRUNCATED-NEXT: Offset: 0x1F
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# TRUNCATED-NEXT: Size: 0xD
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# TRUNCATED-NEXT: HasReturn: No
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# TRUNCATED-NEXT: HasTailCall: Yes
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# TRUNCATED-NEXT: IsEHPad: Yes
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# TRUNCATED-NEXT: CanFallThrough: Yes
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# TRUNCATED-NEXT: }
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# TRUNCATED-NEXT: ]
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# TRUNCATED-NEXT: }
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# TRUNCATED-NEXT: ]
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--- !ELF
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FileHeader:
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Class: ELFCLASS[[BITS]]
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Data: ELFDATA2LSB
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Type: ET_EXEC
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Sections:
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- Name: .text
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Type: SHT_PROGBITS
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Flags: [SHF_ALLOC]
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- Name: .text.bar
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Type: SHT_PROGBITS
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Flags: [SHF_ALLOC]
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- Name: .llvm_bb_addr_map
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Type: SHT_LLVM_BB_ADDR_MAP
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ShSize: [[SIZE=<none>]]
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Link: .text
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Entries:
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- Version: 2
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Address: [[ADDR=0x11111]]
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BBEntries:
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- ID: 0
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AddressOffset: 0x0
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Size: 0x1
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Metadata: 0xF0000002
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- ID: 2
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AddressOffset: 0x3
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Size: 0x4
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Metadata: 0x5
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- Version: 2
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Address: 0x22222
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BBEntries:
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- ID: 4
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AddressOffset: 0x6
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Size: 0x7
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Metadata: 0x8
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- Name: dummy_section
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Type: SHT_PROGBITS
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Size: 16
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- Name: '.llvm_bb_addr_map (1)'
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Type: SHT_LLVM_BB_ADDR_MAP
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Link: .text.bar
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Entries:
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- Version: 2
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Address: 0x33333
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BBEntries:
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- ID: 6
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AddressOffset: 0x9
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Size: 0xa
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Metadata: 0xb
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- ID: 7
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AddressOffset: 0xc
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Size: 0xd
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Metadata: 0xe
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Symbols:
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- Name: foo
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Section: .text
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Type: STT_FUNC
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Value: 0x22222
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- Name: bar
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Section: .text.bar
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Type: STT_FUNC
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Value: 0x33333
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## Check that using the SHT_LLVM_BB_ADDR_MAP_V0 section type generates the same
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## result as using the SHT_LLVM_BB_ADDR_MAP section type with Version=0.
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## The Version field is required even for SHT_LLVM_BB_ADDR_MAP_V0 but it
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## should not impact the result. This unideal behavior will be gone once
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## SHT_LLVM_BB_ADDR_MAP_V0 is deprecated.
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# RUN: yaml2obj --docnum=2 %s -DVERSION=255 -DSECTION_TYPE=SHT_LLVM_BB_ADDR_MAP_V0 -o %t2.type0
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# RUN: llvm-readobj %t2.type0 --bb-addr-map 2>&1 | FileCheck %s --check-prefix=V0
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# RUN: yaml2obj --docnum=2 %s -DVERSION=0 -DSECTION_TYPE=SHT_LLVM_BB_ADDR_MAP -o %t2.version0
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# RUN: llvm-readobj %t2.version0 --bb-addr-map 2>&1 | FileCheck %s --check-prefix=V0
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# V0: BBAddrMap [
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# V0-NEXT: Function {
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# V0-NEXT: At: 0x11111
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# V0-NEXT: Name: foo
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# V0-NEXT: BB entries [
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# V0-NEXT: {
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# V0-NEXT: ID: 0
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# V0-NEXT: Offset: 0x1
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# V0-NEXT: Size: 0x2
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# V0-NEXT: HasReturn:
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# V0-NEXT: HasTailCall:
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# V0-NEXT: IsEHPad:
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# V0-NEXT: CanFallThrough:
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# V0-NEXT: }
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# V0-NEXT: {
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# V0-NEXT: ID: 1
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# V0-NEXT: Offset: 0x4
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# V0-NEXT: Size: 0x5
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# V0-NEXT: HasReturn:
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# V0-NEXT: HasTailCall:
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# V0-NEXT: IsEHPad:
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# V0-NEXT: CanFallThrough:
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# V0-NEXT: }
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# V0-NEXT: ]
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# V0-NEXT: }
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## Check version 1 (without BB IDs).
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# RUN: yaml2obj --docnum=2 %s -DVERSION=1 -DSECTION_TYPE=SHT_LLVM_BB_ADDR_MAP -o %t3
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# RUN: llvm-readobj %t3 --bb-addr-map 2>&1 | FileCheck %s --check-prefix=V1
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# V1: BBAddrMap [
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# V1-NEXT: Function {
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# V1-NEXT: At: 0x11111
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# V1-NEXT: Name: foo
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# V1-NEXT: BB entries [
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# V1-NEXT: {
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# V1-NEXT: ID: 0
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# V1-NEXT: Offset: 0x1
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# V1-NEXT: Size: 0x2
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# V1-NEXT: HasReturn:
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# V1-NEXT: HasTailCall:
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# V1-NEXT: IsEHPad:
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# V1-NEXT: CanFallThrough:
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# V1-NEXT: }
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# V1-NEXT: {
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# V1-NEXT: ID: 1
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# V1-NEXT: Offset: 0x7
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# V1-NEXT: Size: 0x5
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# V1-NEXT: HasReturn:
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# V1-NEXT: HasTailCall:
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# V1-NEXT: IsEHPad:
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# V1-NEXT: CanFallThrough:
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# V1-NEXT: }
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# V1-NEXT: ]
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# V1-NEXT: }
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--- !ELF
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FileHeader:
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Class: ELFCLASS64
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Data: ELFDATA2LSB
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Type: ET_EXEC
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Sections:
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- Name: .text.foo
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Type: SHT_PROGBITS
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Flags: [SHF_ALLOC]
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- Name: .llvm_bb_addr_map
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Type: [[SECTION_TYPE]]
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Link: .text.foo
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Entries:
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- Version: [[VERSION]]
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Address: 0x11111
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BBEntries:
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- AddressOffset: 0x1
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Size: 0x2
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Metadata: 0x3
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- AddressOffset: 0x4
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Size: 0x5
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Metadata: 0x6
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Symbols:
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- Name: foo
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Section: .text.foo
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Type: STT_FUNC
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Value: 0x11111
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