5ae8575296
* x64: Take SIGFPE signals for divide traps Prior to this commit Wasmtime would configure `avoid_div_traps=true` unconditionally for Cranelift. This, for the division-based instructions, would change emitted code to explicitly trap on trap conditions instead of letting the `div` x86 instruction trap. There's no specific reason for Wasmtime, however, to specifically avoid traps in the `div` instruction. This means that the extra generated branches on x86 aren't necessary since the `div` and `idiv` instructions already trap for similar conditions as wasm requires. This commit instead disables the `avoid_div_traps` setting for Wasmtime's usage of Cranelift. Subsequently the codegen rules were updated slightly: * When `avoid_div_traps=true`, traps are no longer emitted for `div` instructions. * The `udiv`/`urem` instructions now list their trap as divide-by-zero instead of integer overflow. * The lowering for `sdiv` was updated to still explicitly check for zero but the integer overflow case is deferred to the instruction itself. * The lowering of `srem` no longer checks for zero and the listed trap for the `div` instruction is a divide-by-zero. This means that the codegen for `udiv` and `urem` no longer have any branches. The codegen for `sdiv` removes one branch but keeps the zero-check to differentiate the two kinds of traps. The codegen for `srem` removes one branch but keeps the -1 check since the semantics of `srem` mismatch with the semantics of `idiv` with a -1 divisor (specifically for INT_MIN). This is unlikely to have really all that much of a speedup but was something I noticed during #6008 which seemed like it'd be good to clean up. Plus Wasmtime's signal handling was already set up to catch `SIGFPE`, it was just never firing. * Remove the `avoid_div_traps` cranelift setting With no known users currently removing this should be possible and helps simplify the x64 backend. * x64: GC more support for avoid_div_traps Remove the `validate_sdiv_divisor*` pseudo-instructions and clean up some of the ISLE rules now that `div` is allowed to itself trap unconditionally. * x64: Store div trap code in instruction itself * Keep divisors in registers, not in memory Don't accidentally fold multiple traps together * Handle EXC_ARITHMETIC on macos * Update emit tests * Update winch and tests
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.