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cranelift: add a new resumable_trapnz instruction;

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This is useful to have to allow resumable_trap to happen in loop
headers, for instance. This is the correct way to implement interrupt
checks in Spidermonkey, which are effectively resumable traps. Previous
implementation was using traps, which is wrong, since traps semantically
can't be resumed after.
This commit is contained in:
Benjamin Bouvier
2020-06-12 12:58:36 +02:00
parent 60d55a3483
commit dad56a2488
4 changed files with 36 additions and 12 deletions
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16
cranelift/codegen/meta/src/shared/instructions.rs
View File

@@ -340,7 +340,21 @@ fn define_control_flow(
r#"
Trap when non-zero.
if ``c`` is zero, execution continues at the following instruction.
If ``c`` is zero, execution continues at the following instruction.
"#,
&formats.cond_trap,
)
.operands_in(vec![c, code])
.can_trap(true),
);
ig.push(
Inst::new(
"resumable_trapnz",
r#"
A resumable trap to be called when the passed condition is non-zero.
If ``c`` is zero, execution continues at the following instruction.
"#,
&formats.cond_trap,
)

2
cranelift/codegen/meta/src/shared/legalize.rs
View File

@@ -99,6 +99,7 @@ pub(crate) fn define(insts: &InstructionGroup, imm: &Immediates) -> TransformGro
let jump = insts.by_name("jump");
let load = insts.by_name("load");
let popcnt = insts.by_name("popcnt");
let resumable_trapnz = insts.by_name("resumable_trapnz");
let rotl = insts.by_name("rotl");
let rotl_imm = insts.by_name("rotl_imm");
let rotr = insts.by_name("rotr");
@@ -138,6 +139,7 @@ pub(crate) fn define(insts: &InstructionGroup, imm: &Immediates) -> TransformGro
// TODO: Add sufficient XForm syntax that we don't need to hand-code these.
expand.custom_legalize(trapz, "expand_cond_trap");
expand.custom_legalize(trapnz, "expand_cond_trap");
expand.custom_legalize(resumable_trapnz, "expand_cond_trap");
expand.custom_legalize(br_table, "expand_br_table");
expand.custom_legalize(select, "expand_select");
widen.custom_legalize(select, "expand_select"); // small ints