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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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25
cranelift/interpreter/src/step.rs
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@@ -245,10 +245,7 @@ where
let branch_when = |condition: bool| -> Result<ControlFlow<V>, StepError> {
let branch_args = match inst {
InstructionData::Jump { .. } => args_range(0..),
InstructionData::BranchInt { .. }
| InstructionData::BranchFloat { .. }
| InstructionData::Branch { .. } => args_range(1..),
InstructionData::BranchIcmp { .. } => args_range(2..),
InstructionData::Branch { .. } => args_range(1..),
_ => panic!("Unrecognized branch inst: {:?}", inst),
}?;
@@ -293,11 +290,6 @@ where
.convert(ValueConversionKind::ToBoolean)?
.into_bool()?,
)?,
Opcode::BrIcmp => {
branch_when(icmp(ctrl_ty, inst.cond_code().unwrap(), &arg(0)?, &arg(1)?)?.into_bool()?)?
}
Opcode::Brif => branch_when(state.has_iflag(inst.cond_code().unwrap()))?,
Opcode::Brff => branch_when(state.has_fflag(inst.fp_cond_code().unwrap()))?,
Opcode::BrTable => {
if let InstructionData::BranchTable {
table, destination, ..
@@ -554,8 +546,7 @@ where
Opcode::Null => unimplemented!("Null"),
Opcode::Nop => ControlFlow::Continue,
Opcode::Select => choose(arg(0)?.into_bool()?, arg(1)?, arg(2)?),
Opcode::Selectif => choose(state.has_iflag(inst.cond_code().unwrap()), arg(1)?, arg(2)?),
Opcode::SelectifSpectreGuard => unimplemented!("SelectifSpectreGuard"),
Opcode::SelectSpectreGuard => unimplemented!("SelectSpectreGuard"),
Opcode::Bitselect => {
let mask_a = Value::and(arg(0)?, arg(1)?)?;
let mask_b = Value::and(Value::not(arg(0)?)?, arg(2)?)?;
@@ -940,18 +931,6 @@ where
Opcode::Nearest => assign(Value::nearest(arg(0)?)?),
Opcode::IsNull => unimplemented!("IsNull"),
Opcode::IsInvalid => unimplemented!("IsInvalid"),
// `ctrl_ty` is `INVALID` for `Trueif` and `Trueff`, but both should
// return a 1-bit boolean value.
Opcode::Trueif => choose(
state.has_iflag(inst.cond_code().unwrap()),
Value::bool(true, false, types::I8)?,
Value::bool(false, false, types::I8)?,
),
Opcode::Trueff => choose(
state.has_fflag(inst.fp_cond_code().unwrap()),
Value::bool(true, false, types::I8)?,
Value::bool(false, false, types::I8)?,
),
Opcode::Bitcast | Opcode::RawBitcast | Opcode::ScalarToVector => {
let input_ty = inst_context.type_of(inst_context.args()[0]).unwrap();
let arg0 = extractlanes(&arg(0)?, input_ty)?;