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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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29
cranelift/fuzzgen/src/function_generator.rs
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@@ -812,7 +812,6 @@ enum BlockTerminator {
Return,
Jump(Block),
Br(Block, Block),
BrIcmp(Block, Block),
BrTable(Block, Vec<Block>),
Switch(Type, Block, HashMap<u128, Block>),
}
@@ -822,7 +821,6 @@ enum BlockTerminatorKind {
Return,
Jump,
Br,
BrIcmp,
BrTable,
Switch,
}
@@ -1101,19 +1099,6 @@ where
}
builder.ins().jump(right, &right_args[..]);
}
BlockTerminator::BrIcmp(left, right) => {
let cc = *self.u.choose(IntCC::all())?;
let _type = *self.u.choose(&[I8, I16, I32, I64, I128])?;
let lhs = builder.use_var(self.get_variable_of_type(_type)?);
let rhs = builder.use_var(self.get_variable_of_type(_type)?);
let left_args = self.generate_values_for_block(builder, left)?;
let right_args = self.generate_values_for_block(builder, right)?;
builder.ins().br_icmp(cc, lhs, rhs, left, &left_args[..]);
builder.ins().jump(right, &right_args[..]);
}
BlockTerminator::BrTable(default, targets) => {
// Create jump tables on demand
let jt = builder.create_jump_table(JumpTableData::with_blocks(targets));
@@ -1295,13 +1280,10 @@ where
valid_terminators.push(BlockTerminatorKind::Return);
} else {
// If we have more than one block we can allow terminators that target blocks.
// TODO: We could add some kind of BrReturn/BrIcmpReturn here, to explore edges where we exit
// in the middle of the function
valid_terminators.extend_from_slice(&[
BlockTerminatorKind::Jump,
BlockTerminatorKind::Br,
BlockTerminatorKind::BrIcmp,
]);
// TODO: We could add some kind of BrReturn here, to explore edges where we
// exit in the middle of the function
valid_terminators
.extend_from_slice(&[BlockTerminatorKind::Jump, BlockTerminatorKind::Br]);
}
// BrTable and the Switch interface only allow targeting blocks without params
@@ -1323,9 +1305,6 @@ where
BlockTerminatorKind::Br => {
BlockTerminator::Br(next_block, self.generate_target_block(block)?)
}
BlockTerminatorKind::BrIcmp => {
BlockTerminator::BrIcmp(next_block, self.generate_target_block(block)?)
}
// TODO: Allow generating backwards branches here
BlockTerminatorKind::BrTable => {
// Make the default the next block, and then we don't have to worry