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compiler(arm64): avoid conditional jumps to the trap handler (#1524)

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Signed-off-by: Edoardo Vacchi <evacchi@users.noreply.github.com>
This commit is contained in:
Edoardo Vacchi
2023-06-19 11:18:18 +02:00
committed by GitHub
parent b01ba67fdc
commit ea63499005
2 changed files with 50 additions and 30 deletions
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34
internal/engine/compiler/impl_arm64.go
View File

@@ -380,42 +380,16 @@ func (c *arm64Compiler) compileReturnFunction() error {
}
func (c *arm64Compiler) compileMaybeExitFromNativeCode(skipCondition asm.Instruction, status nativeCallStatusCode) {
if target := c.compiledTrapTargets[status]; target != nil {
// We've already compiled this.
// Invert the condition to jump into the appropriate target.
var trapCondition asm.Instruction
switch skipCondition {
case arm64.BCONDEQ:
trapCondition = arm64.BCONDNE
case arm64.BCONDNE:
trapCondition = arm64.BCONDEQ
case arm64.BCONDLO:
trapCondition = arm64.BCONDHS
case arm64.BCONDHS:
trapCondition = arm64.BCONDLO
case arm64.BCONDLS:
trapCondition = arm64.BCONDHI
case arm64.BCONDHI:
trapCondition = arm64.BCONDLS
case arm64.BCONDVS:
trapCondition = arm64.BCONDVC
case arm64.BCONDVC:
trapCondition = arm64.BCONDVS
default:
panic("BUG: couldn't invert condition")
}
c.assembler.CompileJump(trapCondition).AssignJumpTarget(target)
} else {
skip := c.assembler.CompileJump(skipCondition)
c.compileExitFromNativeCode(status)
c.assembler.SetJumpTargetOnNext(skip)
}
skip := c.assembler.CompileJump(skipCondition)
c.compileExitFromNativeCode(status)
c.assembler.SetJumpTargetOnNext(skip)
}
// compileExitFromNativeCode adds instructions to give the control back to ce.exec with the given status code.
func (c *arm64Compiler) compileExitFromNativeCode(status nativeCallStatusCode) {
if target := c.compiledTrapTargets[status]; target != nil {
c.assembler.CompileJump(arm64.B).AssignJumpTarget(target)
return
}
switch status {

46
internal/engine/compiler/impl_arm64_test.go
View File

@@ -236,6 +236,52 @@ func TestArm64Compiler_getSavedTemporaryLocationStack(t *testing.T) {
})
}
// https://github.com/tetratelabs/wazero/issues/1522
func TestArm64Compiler_LargeTrapOffsets(t *testing.T) {
env := newCompilerEnvironment()
compiler := env.requireNewCompiler(t, &wasm.FunctionType{}, newCompiler, &wazeroir.CompilationResult{
Types: []wasm.FunctionType{{}},
})
err := compiler.compilePreamble()
require.NoError(t, err)
one := operationPtr(wazeroir.NewOperationConstI32(uint32(1)))
five := operationPtr(wazeroir.NewOperationConstI32(uint32(5)))
div := operationPtr(wazeroir.NewOperationDiv(wazeroir.SignedTypeInt32))
// Place the offset value.
err = compiler.compileConstI32(one)
require.NoError(t, err)
// Repeat enough times that jump labels are not within (-524288, 524287).
// Relative offset -2097164/4(=-524291).
// At the time of writing, 52429 is empirically the value that starts
// triggering the bug on arm64. We impose an arbitrarily higher value
// to account for possible future improvement to the number of instructions
// we emit.
for i := 0; i < 80_000; i++ {
err = compiler.compileConstI32(five)
require.NoError(t, err)
err = compiler.compileDiv(div)
require.NoError(t, err)
}
err = compiler.compileReturnFunction()
require.NoError(t, err)
code := asm.CodeSegment{}
defer func() { require.NoError(t, code.Unmap()) }()
// Generate the code under test and run.
_, err = compiler.compile(code.NextCodeSection())
require.NoError(t, err)
env.exec(code.Bytes())
require.Equal(t, nativeCallStatusCodeReturned.String(), env.compilerStatus().String())
}
// compile implements compilerImpl.setStackPointerCeil for the amd64 architecture.
func (c *arm64Compiler) setStackPointerCeil(v uint64) {
c.stackPointerCeil = v