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Refactor how SwitchInt stores jump targets

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This commit is contained in:
Jonas Schievink 2020-10-10 17:36:04 +02:00
parent cae8bc1f23
commit 432535da2b
22 changed files with 247 additions and 206 deletions
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45
compiler/rustc_codegen_ssa/src/mir/block.rs
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@ -12,9 +12,9 @@ use crate::MemFlags;
use rustc_ast as ast;
use rustc_hir::lang_items::LangItem;
use rustc_index::vec::Idx;
use rustc_middle::mir;
use rustc_middle::mir::interpret::ConstValue;
use rustc_middle::mir::AssertKind;
use rustc_middle::mir::{self, SwitchTargets};
use rustc_middle::ty::layout::{FnAbiExt, HasTyCtxt};
use rustc_middle::ty::print::with_no_trimmed_paths;
use rustc_middle::ty::{self, Instance, Ty, TypeFoldable};
@ -24,8 +24,6 @@ use rustc_target::abi::call::{ArgAbi, FnAbi, PassMode};
use rustc_target::abi::{self, LayoutOf};
use rustc_target::spec::abi::Abi;
use std::borrow::Cow;
/// Used by `FunctionCx::codegen_terminator` for emitting common patterns
/// e.g., creating a basic block, calling a function, etc.
struct TerminatorCodegenHelper<'tcx> {
@ -198,42 +196,37 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
mut bx: Bx,
discr: &mir::Operand<'tcx>,
switch_ty: Ty<'tcx>,
values: &Cow<'tcx, [u128]>,
targets: &Vec<mir::BasicBlock>,
targets: &SwitchTargets<'tcx>,
) {
let discr = self.codegen_operand(&mut bx, &discr);
// `switch_ty` is redundant, sanity-check that.
assert_eq!(discr.layout.ty, switch_ty);
if targets.len() == 2 {
// If there are two targets, emit br instead of switch
let lltrue = helper.llblock(self, targets[0]);
let llfalse = helper.llblock(self, targets[1]);
helper.maybe_sideeffect(self.mir, &mut bx, targets.all_targets());
let mut target_iter = targets.iter();
if target_iter.len() == 1 {
// If there are two targets (one conditional, one fallback), emit br instead of switch
let (test_value, target) = target_iter.next().unwrap();
let lltrue = helper.llblock(self, target);
let llfalse = helper.llblock(self, targets.otherwise());
if switch_ty == bx.tcx().types.bool {
helper.maybe_sideeffect(self.mir, &mut bx, targets.as_slice());
// Don't generate trivial icmps when switching on bool
if let [0] = values[..] {
bx.cond_br(discr.immediate(), llfalse, lltrue);
} else {
assert_eq!(&values[..], &[1]);
bx.cond_br(discr.immediate(), lltrue, llfalse);
match test_value {
0 => bx.cond_br(discr.immediate(), llfalse, lltrue),
1 => bx.cond_br(discr.immediate(), lltrue, llfalse),
_ => bug!(),
}
} else {
let switch_llty = bx.immediate_backend_type(bx.layout_of(switch_ty));
let llval = bx.const_uint_big(switch_llty, values[0]);
let llval = bx.const_uint_big(switch_llty, test_value);
let cmp = bx.icmp(IntPredicate::IntEQ, discr.immediate(), llval);
helper.maybe_sideeffect(self.mir, &mut bx, targets.as_slice());
bx.cond_br(cmp, lltrue, llfalse);
}
} else {
helper.maybe_sideeffect(self.mir, &mut bx, targets.as_slice());
let (otherwise, targets) = targets.split_last().unwrap();
bx.switch(
discr.immediate(),
helper.llblock(self, *otherwise),
values
.iter()
.zip(targets)
.map(|(&value, target)| (value, helper.llblock(self, *target))),
helper.llblock(self, targets.otherwise()),
target_iter.map(|(value, target)| (value, helper.llblock(self, target))),
);
}
}
@ -975,8 +968,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
helper.funclet_br(self, &mut bx, target);
}
mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref values, ref targets } => {
self.codegen_switchint_terminator(helper, bx, discr, switch_ty, values, targets);
mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref targets } => {
self.codegen_switchint_terminator(helper, bx, discr, switch_ty, targets);
}
mir::TerminatorKind::Return => {