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A number of places in the x64 backend make use of 128-bit constants for various wasm SIMD-related instructions although most of them currently use the `x64_xmm_load_const` helper to load the constant into a register. Almost all xmm instructions, however, enable using a memory operand which means that these loads can be folded into instructions to help reduce register pressure. Automatic conversions were added for a `VCodeConstant` into an `XmmMem` value and then explicit loads were all removed in favor of forwarding the `XmmMem` value directly to the underlying instruction. Note that some instances of `x64_xmm_load_const` remain since they're used in contexts where load sinking won't work (e.g. they're the first operand, not the second for non-commutative instructions).
filetests
Filetests is a crate that contains multiple test suites for testing
various parts of cranelift. Each folder under cranelift/filetests/filetests is a different
test suite that tests different parts.
Adding a runtest
One of the available testsuites is the "runtest" testsuite. Its goal is to compile some piece of clif code, run it and ensure that what comes out is what we expect.
To build a run test you can add the following to a file:
test interpret
test run
target x86_64
target aarch64
target s390x
function %band_f32(f32, f32) -> f32 {
block0(v0: f32, v1: f32):
v2 = band v0, v1
return v2
}
; run: %band_f32(0x0.5, 0x1.0) == 0x1.5
Since this is a run test for band we can put it in: runtests/band.clif.
Once we have the file in the test suite we can run it by invoking: cargo run -- test filetests/filetests/runtests/band.clif from the cranelift directory.
The first lines tell clif-util what kind of tests we want to run on this file.
test interpret invokes the interpreter and checks if the conditions in the ; run comments pass. test run does the same, but compiles the file and runs it as a native binary.
For more information about testing see testing.md.