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cranelift: Remove redundant branch and select instructions (#5097)

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As discussed in the 2022/10/19 meeting, this PR removes many of the branch and select instructions that used iflags, in favor if using brz/brnz and select in their place. Additionally, it reworks selectif_spectre_guard to take an i8 input instead of an iflags input.

For reference, the removed instructions are: br_icmp, brif, brff, trueif, trueff, and selectif.
This commit is contained in:
Trevor Elliott
2022-10-24 16:14:35 -07:00
committed by GitHub
parent 30589170b4
commit ec12415b1f
40 changed files with 579 additions and 2527 deletions
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4
cranelift/codegen/src/legalizer/heap.rs
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@@ -250,11 +250,11 @@ fn compute_addr(
if let Some((cc, a, b)) = spectre_oob_comparison {
let final_addr = pos.ins().iadd(base, offset);
let zero = pos.ins().iconst(addr_ty, 0);
let flags = pos.ins().ifcmp(a, b);
let cmp = pos.ins().icmp(cc, a, b);
pos.func
.dfg
.replace(inst)
.selectif_spectre_guard(addr_ty, cc, flags, zero, final_addr);
.select_spectre_guard(cmp, zero, final_addr);
} else {
pos.func.dfg.replace(inst).iadd(base, offset);
}