T0b1/wasmtime
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

When splitting a const, insert prior to the terminal branch group. (#1325)

Browse Source 
* When splitting a const, insert prior to the terminal branch group. Closes #1159

Given code like the following, on x86_64, which does not have i128 registers:

    ebb0(v0: i64):
        v1 = iconst.i128 0
        v2 = icmp_imm eq v0, 1
        brnz v2, ebb1
        jump ebb2(v1)

It would be split to:

    ebb0(v0: i64):
        v1 = iconst.i128 0
        v2 = icmp_imm eq v0, 1
        brnz v2, ebb1
        v3, v4 = isplit.i128 v1
        jump ebb2(v3, v4)

But that fails basic-block invariants. This patch changes that to:

    ebb0(v0: i64):
        v1 = iconst.i128 0
        v2 = icmp_imm eq v0, 1
        v3, v4 = isplit.i128 v1
        brnz v2, ebb1
        jump ebb2(v3, v4)

* Add isplit-bb.clif testcase
This commit is contained in:
Sean Stangl
2020-01-22 09:14:41 -07:00
committed by Benjamin Bouvier
parent d6134a6f3a
commit b4c6bfd371
3 changed files with 55 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
cranelift/codegen/src/ir/layout.rs
View File

@@ -4,6 +4,7 @@
//! determined by the `Layout` data structure defined in this module.
use crate::entity::SecondaryMap;
use crate::ir::dfg::DataFlowGraph;
use crate::ir::progpoint::{ExpandedProgramPoint, ProgramOrder};
use crate::ir::{Ebb, Inst};
use crate::packed_option::PackedOption;
@@ -573,6 +574,19 @@ impl Layout {
self.insts[inst].prev.expand()
}
/// Fetch the first instruction in an ebb's terminal branch group.
pub fn canonical_branch_inst(&self, dfg: &DataFlowGraph, ebb: Ebb) -> Option<Inst> {
// Basic blocks permit at most two terminal branch instructions.
// If two, the former is conditional and the latter is unconditional.
let last = self.last_inst(ebb)?;
if let Some(prev) = self.prev_inst(last) {
if dfg[prev].opcode().is_branch() {
return Some(prev);
}
}
Some(last)
}
/// Insert `inst` before the instruction `before` in the same EBB.
pub fn insert_inst(&mut self, inst: Inst, before: Inst) {
debug_assert_eq!(self.inst_ebb(inst), None);