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Legalize trapz/trapnz to a BB-like format.

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This commit is contained in:
Nicolas B. Pierron
2019-07-09 16:02:49 +02:00
committed by GitHub
parent f11fc34066
commit 1963c223b1
5 changed files with 87 additions and 41 deletions
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32
cranelift/codegen/src/legalizer/mod.rs
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@@ -150,29 +150,45 @@ fn expand_cond_trap(
// Split the EBB after `inst`:
//
// trapnz arg
// ..
//
// Becomes:
//
// brz arg, new_ebb
// trap
// new_ebb:
// brz arg, new_ebb_resume
// jump new_ebb_trap
//
// new_ebb_trap:
// trap
//
// new_ebb_resume:
// ..
let old_ebb = func.layout.pp_ebb(inst);
let new_ebb = func.dfg.make_ebb();
let new_ebb_trap = func.dfg.make_ebb();
let new_ebb_resume = func.dfg.make_ebb();
// Replace trap instruction by the inverted condition.
if trapz {
func.dfg.replace(inst).brnz(arg, new_ebb, &[]);
func.dfg.replace(inst).brnz(arg, new_ebb_resume, &[]);
} else {
func.dfg.replace(inst).brz(arg, new_ebb, &[]);
func.dfg.replace(inst).brz(arg, new_ebb_resume, &[]);
}
// Add jump instruction after the inverted branch.
let mut pos = FuncCursor::new(func).after_inst(inst);
pos.use_srcloc(inst);
pos.ins().jump(new_ebb_trap, &[]);
// Insert the new label and the unconditional trap terminator.
pos.insert_ebb(new_ebb_trap);
pos.ins().trap(code);
pos.insert_ebb(new_ebb);
// Insert the new label and resume the execution when the trap fails.
pos.insert_ebb(new_ebb_resume);
// Finally update the CFG.
cfg.recompute_ebb(pos.func, old_ebb);
cfg.recompute_ebb(pos.func, new_ebb);
cfg.recompute_ebb(pos.func, new_ebb_resume);
cfg.recompute_ebb(pos.func, new_ebb_trap);
}
/// Jump tables.