Even though in `Subtarget` we defined `SIMDLevel` as a number so
`hasRelaxedSIMD` automatically means `hasSIMD128`,
0caf0c93e7/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h (L36-L40)0caf0c93e7/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h (L107)
specifying only `relaxed-simd` feature on a program that needs `simd128`
instructions to compile fails, because of this query in `AsmPrinter`:
d0d05aec3b/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp (L644-L645)
This `verifyInstructionPredicates` function (and other functions called
by this function) is generated by
https://github.com/llvm/llvm-project/blob/main/llvm/utils/TableGen/InstrInfoEmitter.cpp,
and looks like this (you can check it in the
`lib/Target/WebAssembly/WebAssemblyGenInstrInfo.inc` in your build
directory):
```cpp
void verifyInstructionPredicates(
unsigned Opcode, const FeatureBitset &Features) {
FeatureBitset AvailableFeatures = computeAvailableFeatures(Features);
FeatureBitset RequiredFeatures = computeRequiredFeatures(Opcode);
FeatureBitset MissingFeatures =
(AvailableFeatures & RequiredFeatures) ^
RequiredFeatures;
...
}
```
And `computeAvailableFeatures` is just a set query, like this:
```cpp
inline FeatureBitset computeAvailableFeatures(const FeatureBitset &FB) {
FeatureBitset Features;
if (FB[WebAssembly::FeatureAtomics])
Features.set(Feature_HasAtomicsBit);
if (FB[WebAssembly::FeatureBulkMemory])
Features.set(Feature_HasBulkMemoryBit);
if (FB[WebAssembly::FeatureExceptionHandling])
Features.set(Feature_HasExceptionHandlingBit);
...
```
So this is how currently `HasSIMD128` is defined:
0caf0c93e7/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td (L79-L81)
The things being checked in this `computeAvailableFeatures`, and in turn
in `AsmPrinter`, are `AssemblerPredicate`s. These only check which bits
are set in the features set and are different from `Predicate`s, which
can call `Subtarget` functions like `Subtarget->hasSIMD128()`.
But apparently we can use `all_of` and `any_of` directives in
`AssemblerPredicate`, and we can make `simd128`'s `AssemblerPredicate`
set in `relaxed-simd` is set by the condition as an 'or' of the two.
Fixes#98502.
