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SSA Validator Fixes (#105)

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* Don't check for defs on a use of a fixed-nonallocatable operand

* Add traces to the ssa validator to aid debugging

* Format
This commit is contained in:
Trevor Elliott
2022-11-30 16:31:27 -08:00
committed by GitHub
parent 346b7f38a3
commit bc398bd19b
1 changed files with 18 additions and 0 deletions
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18
src/ssa.rs
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@@ -17,6 +17,7 @@ pub fn validate_ssa<F: Function>(f: &F, cfginfo: &CFGInfo) -> Result<(), RegAllo
let block = Block::new(block);
let mut def = |vreg: VReg, inst| {
if defined_in[vreg.vreg()].is_valid() {
trace!("Multiple def constraints for {:?}", vreg);
Err(RegAllocError::SSA(vreg, inst))
} else {
defined_in[vreg.vreg()] = block;
@@ -48,6 +49,12 @@ pub fn validate_ssa<F: Function>(f: &F, cfginfo: &CFGInfo) -> Result<(), RegAllo
for iix in f.block_insns(block).iter() {
let operands = f.inst_operands(iix);
for operand in operands {
// Fixed registers uses will likely not be SSA, but they also
// won't receive assignments.
if operand.as_fixed_nonallocatable().is_some() {
continue;
}
match operand.kind() {
OperandKind::Use => {
let def_block = defined_in[operand.vreg().vreg()];
@@ -58,6 +65,7 @@ pub fn validate_ssa<F: Function>(f: &F, cfginfo: &CFGInfo) -> Result<(), RegAllo
cfginfo.dominates(def_block, block)
};
if !okay {
trace!("Invalid use {:?}", operand.vreg());
return Err(RegAllocError::SSA(operand.vreg(), iix));
}
}
@@ -69,10 +77,12 @@ pub fn validate_ssa<F: Function>(f: &F, cfginfo: &CFGInfo) -> Result<(), RegAllo
// Mod (modify) operands are not used in SSA,
// but can be used by non-SSA code (e.g. with
// the regalloc.rs compatibility shim).
trace!("Unexpected mod {:?}", operand.vreg());
return Err(RegAllocError::SSA(operand.vreg(), iix));
}
}
}
// In SSA form, an instruction can't use a VReg that it
// also defines. So only record this instruction's defs
// after its uses have been checked.
@@ -94,6 +104,7 @@ pub fn validate_ssa<F: Function>(f: &F, cfginfo: &CFGInfo) -> Result<(), RegAllo
for insn in insns.iter() {
if insn == insns.last() {
if !(f.is_branch(insn) || f.is_ret(insn)) {
trace!("block {:?} is not terminated by a branch or ret!", block);
return Err(RegAllocError::BB(block));
}
if f.is_branch(insn) {
@@ -101,12 +112,18 @@ pub fn validate_ssa<F: Function>(f: &F, cfginfo: &CFGInfo) -> Result<(), RegAllo
let blockparams_in = f.block_params(succ);
let blockparams_out = f.branch_blockparams(block, insn, i);
if blockparams_in.len() != blockparams_out.len() {
trace!(
"Mismatch on block params, found {} expected {}",
blockparams_out.len(),
blockparams_in.len()
);
return Err(RegAllocError::Branch(insn));
}
}
}
} else {
if f.is_branch(insn) || f.is_ret(insn) {
trace!("Block terminator found in the middle of a block");
return Err(RegAllocError::BB(block));
}
}
@@ -116,6 +133,7 @@ pub fn validate_ssa<F: Function>(f: &F, cfginfo: &CFGInfo) -> Result<(), RegAllo
// Check that the entry block has no block args: otherwise it is
// undefined what their value would be.
if f.block_params(f.entry_block()).len() > 0 {
trace!("Entry block contains block args");
return Err(RegAllocError::BB(f.entry_block()));
}