Add a convenience wrapper struct for the `bit_value_t` enum type to host various constructors, query, and printing support. Also refactor related code in several places. In `getBitsField`, use `llvm::append_range` and `SmallVector::append()` and eliminate manual loops. Eliminate `emitNameWithID` and instead use the `operator <<` that does the same thing as this function. Have `BitValue::getValue()` (replacement for `Value`) return std::optional<> instead of -1 for unset bits. Terminate with a fatal error when a decoding conflict is encountered.
Add option `use-fn-table-in-decode-to-mcinst` to use a table of function pointers instead of a switch case in the generated `decodeToMCInst` function. When the number of switch cases in this function is large, the generated code takes a long time to compile in release builds. Using a table of function pointers instead improves the compile time significantly (~3x speedup in compiling the code in a downstream target). This option will allow targets to opt into this mode if they desire for better build times. Tested with `check-llvm-mc` with the option enabled by default.
Also assign variable names to different elements of `OpMap` for better readibility, and eliminate `NumberedEncodingsRef` as `std::vector` will automatically get converted to an `ArrayRef`.
TryDecode/CheckPredicate/SoftFail MCD ops are not used by many targets. Track the set of opcodes that were emitted and emit code for handling TryDecode/CheckPredicate/SoftFail ops when decoding only if there were emitted. This is purely eliminating dead code in the generated `decodeInstruction` function. This results in the following reduction in the size of the Disassembler .so files with a release x86_64 release build on Linux: ``` Target Old Size New Size % reduction build/lib/libLLVMAArch64Disassembler.so.21.0git 256656 256656 0.00 build/lib/libLLVMAMDGPUDisassembler.so.21.0git 813000 808168 0.59 build/lib/libLLVMARCDisassembler.so.21.0git 44816 43536 2.86 build/lib/libLLVMARMDisassembler.so.21.0git 281744 278808 1.04 build/lib/libLLVMAVRDisassembler.so.21.0git 36040 34496 4.28 build/lib/libLLVMBPFDisassembler.so.21.0git 26248 23168 11.73 build/lib/libLLVMCSKYDisassembler.so.21.0git 55960 53632 4.16 build/lib/libLLVMHexagonDisassembler.so.21.0git 115952 113416 2.19 build/lib/libLLVMLanaiDisassembler.so.21.0git 24360 21008 13.76 build/lib/libLLVMLoongArchDisassembler.so.21.0git 58584 56168 4.12 build/lib/libLLVMM68kDisassembler.so.21.0git 57264 53880 5.91 build/lib/libLLVMMSP430Disassembler.so.21.0git 28896 28440 1.58 build/lib/libLLVMMipsDisassembler.so.21.0git 123128 120568 2.08 build/lib/libLLVMPowerPCDisassembler.so.21.0git 80656 78096 3.17 build/lib/libLLVMRISCVDisassembler.so.21.0git 154080 150200 2.52 build/lib/libLLVMSparcDisassembler.so.21.0git 42040 39568 5.88 build/lib/libLLVMSystemZDisassembler.so.21.0git 97056 94552 2.58 build/lib/libLLVMVEDisassembler.so.21.0git 83944 81352 3.09 build/lib/libLLVMWebAssemblyDisassembler.so.21.0git 25280 25280 0.00 build/lib/libLLVMX86Disassembler.so.21.0git 2920624 2920624 0.00 build/lib/libLLVMXCoreDisassembler.so.21.0git 48320 44288 8.34 build/lib/libLLVMXtensaDisassembler.so.21.0git 42248 35840 15.17 ```
Automated with clang-tidy -fix -checks=-*,modernize-use-default-member-init
Print DecodeIdx associated with Decode MCD ops in the generated decoder tables. This can help in debugging decode failures by first mapping the Op -> DecodeIdx and then inspecting the code in `decodeToMCInst` associated with that DecodeIdx.
Introduce `OrFail` variants for all MCD Decoder Ops that have
`NumToSKip` encoded with them. This is intended to capture the common
case of jumps to the end of the decoder table which has a `OP_Fail` at
the end. Using the `OrFail` variants of these ops avoid encoding the
`NumToSkip` jump offset for these cases, resulting in a reduction in the
size of the decoder tables (from 5 - 17%). Additionally, for the AArch64
target, the table size reduces enough to switch to using 2-byte
`NumToSkip` encoding instead of existing 3-bytes, resulting in a net 30%
reduction in the size of the decoder table.
The total reduction in the size of the decoder tables for different
targets is as follows (computed using the following command: `for i in
*.inc; do echo -n ``basename $i: ``; grep "MCD::OPC_Fail," $i | awk
'{sum += $2} END { print sum}'; done`)
```
Target Old Size New Size % Reduction
================================================
AArch64 153268 106987 30.20
AMDGPU 412056 340856 17.28
ARC 5061 4605 9.01
ARM 73831 60847 17.59
AVR 1306 1158 11.33
BPF 1927 1795 6.85
CSKY 8692 6922 20.36
Hexagon 41965 34759 17.17
Lanai 982 924 5.91
LoongArch 21629 20035 7.37
M68k 13461 11689 13.16
MSP430 3716 3384 8.93
Mips 31415 25771 17.97
PPC 28931 24771 14.38
RISCV 34800 28352 18.53
Sparc 7432 6236 16.09
SystemZ 32248 29716 7.85
VE 42873 36923 13.88
XCore 2316 2196 5.18
Xtensa 3443 2793 18.88
```
These are identified by misc-include-cleaner. I've filtered out those that break builds. Also, I'm staying away from llvm-config.h, config.h, and Compiler.h, which likely cause platform- or compiler-specific build failures.
- Change `Name`, `SubopNames`, `PrinterMethodName`, and `EncoderMethodNames` to be stored as StringRef. - Also changed `CheckComplexPatMatcher::Name` to StringRef as a fallout from the above. Verified that all the tablegen generated files within LLVM are unchanged.