[all-commits] [llvm/llvm-project] 15715f: [WebAssembly, llvm] Add llvm.wasm.ref.test.func int...

[Hood Chatham via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 15715f4089878640405ac897723f24b30e5f8e03
      https://github.com/llvm/llvm-project/commit/15715f4089878640405ac897723f24b30e5f8e03
  Author: Hood Chatham <roberthoodchatham at gmail.com>
  Date:   2025-07-22 (Tue, 22 Jul 2025)

  Changed paths:
    M llvm/include/llvm/IR/IntrinsicsWebAssembly.td
    M llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
    M llvm/lib/Target/WebAssembly/WebAssemblyISelDAGToDAG.cpp
    M llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
    M llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp
    M llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.h
    A llvm/test/CodeGen/WebAssembly/ref-test-func.ll

  Log Message:
  -----------
  [WebAssembly,llvm] Add llvm.wasm.ref.test.func intrinsic (#147486)

This adds an llvm intrinsic for WebAssembly to test the type of a
function. It is intended for adding a future clang builtin
` __builtin_wasm_test_function_pointer_signature` so we can test whether
calling a function pointer will fail with function signature mismatch.

Since the type of a function pointer is just `ptr` we can't figure out
the expected type from that.
The way I figured out to encode the type was by passing 0's of the
appropriate type to the intrinsic.
The first argument gives the expected type of the return type and the
later values give the expected
type of the arguments. So
```llvm
@llvm.wasm.ref.test.func(ptr %func, float 0.000000e+00, double 0.000000e+00, i32 0)
```
tests if `%func` is of type `(double, i32) -> (i32)`. It will lower to:
```wat
local.get $func
table.get $__indirect_function_table
ref.test (double, i32) -> (i32)
```
To indicate the function should be void, I somewhat arbitrarily picked
`token poison`, so the following tests for `(i32) -> ()`:
```llvm
@llvm.wasm.ref.test.func(ptr %func, token poison, i32 0)
```

To lower this intrinsic, we need some place to put the type information.
With `encodeFunctionSignature()` we encode the signature information
into an `APInt`. We decode it in `lowerEncodedFunctionSignature` in
`WebAssemblyMCInstLower.cpp`.



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