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asm: add a backward liveness check for the CFG

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This commit is contained in:
gingerBill
2026-08-24 23:35:41 +01:00
parent a9068261bf
commit e093329012
2 changed files with 166 additions and 14 deletions
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40
src/check_asm.cpp
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@@ -1107,7 +1107,7 @@ gb_internal void check_operand_constraints(AsmCtx *asm_ctx, Slice<Operand> const
}
template <typename AsmCtx>
gb_internal void check_mnemonic(AsmCtx *asm_ctx, CheckerContext *ctx, Entity *tmpl_entity, AstAsmInstruction *instr,
gb_internal bool check_mnemonic(AsmCtx *asm_ctx, CheckerContext *ctx, Entity *tmpl_entity, AstAsmInstruction *instr,
u16 mnemonic, u16 pseudo_mnemonic, Slice<Operand> const &operands,
u8 previous_prefix, Ast *previous_prefix_instr,
AsmCfg *cfg) {
@@ -1514,7 +1514,7 @@ gb_internal void check_mnemonic(AsmCtx *asm_ctx, CheckerContext *ctx, Entity *tm
error(instr->name, "The asm instruction '%.*s' expects %d..=%d operands, got %td", LIT(name), min_count, max_count, operands.count);
}
print_possible_forms();
return;
return false;
}
if (matched) {
@@ -1687,8 +1687,20 @@ gb_internal void check_mnemonic(AsmCtx *asm_ctx, CheckerContext *ctx, Entity *tm
// A read of the view is a read of the source
if (cast(u16)clobber.read & (1u << slot)) {
array_add(&facts->read_params, src_e);
i32 di = -1;
for_array(k, decls) {
if (decls[k].entity == pe) {
di = cast(i32)k;
break;
}
}
if (di >= 0 && decls[di].view_of >= 0 && decls[decls[di].view_of].entity != nullptr) {
array_add(&facts->read_params, decls[decls[di].view_of].entity);
} else {
array_add(&facts->read_params, pe);
}
}
// A write of the view defines the source only if it covers the parent
if (cast(u16)clobber.written & (1u << slot)) {
i32 parent_w = check_asm_operand_bit_width(src_e->type);
@@ -1766,8 +1778,10 @@ gb_internal void check_mnemonic(AsmCtx *asm_ctx, CheckerContext *ctx, Entity *tm
cfg->impure_reason = why;
cfg->impure_reason_node = instr->name;
}
// NOTE(bill): return true even on a purity test because the instruction is still good
}
return;
return true;
}
// NOTE(bill): Failure path
@@ -1878,6 +1892,8 @@ gb_internal void check_mnemonic(AsmCtx *asm_ctx, CheckerContext *ctx, Entity *tm
print_possible_forms();
}
end_error_block();
return false;
}
@@ -2461,6 +2477,7 @@ gb_internal void check_asm_template(AsmCtx *asm_ctx, CheckerContext *ctx, Entity
u8 previous_prefix = 0;
Ast *previous_prefix_instr = nullptr; // for a good error location
bool all_instructions_good = true;
for (Ast *instruction_ : at->instructions) {
switch (instruction_->kind) {
@@ -2489,9 +2506,9 @@ gb_internal void check_asm_template(AsmCtx *asm_ctx, CheckerContext *ctx, Entity
previous_prefix_instr = instruction_;
} else if (res == CheckMnemomic_Mnemonic) {
instr->suffix_flags = suffix_flags;
check_mnemonic(asm_ctx, ctx, entity, instr, mnemonic, 0, slice_from_array(operands),
previous_prefix, previous_prefix_instr,
&cfg);
all_instructions_good &= check_mnemonic(asm_ctx, ctx, entity, instr, mnemonic, 0, slice_from_array(operands),
previous_prefix, previous_prefix_instr,
&cfg);
cfg.saw_any_instructions = true;
@@ -2503,9 +2520,9 @@ gb_internal void check_asm_template(AsmCtx *asm_ctx, CheckerContext *ctx, Entity
u16 pseudo_mnemonic = cast(u16)mnemonic;
auto alias = asm_ctx->pseudo_alias(cast(u16)pseudo_mnemonic);
u16 target_mnemonic = cast(u16)alias.target;
check_mnemonic(asm_ctx, ctx, entity, instr, target_mnemonic, pseudo_mnemonic, slice_from_array(operands),
previous_prefix, previous_prefix_instr,
&cfg);
all_instructions_good &=check_mnemonic(asm_ctx, ctx, entity, instr, target_mnemonic, pseudo_mnemonic, slice_from_array(operands),
previous_prefix, previous_prefix_instr,
&cfg);
cfg.saw_any_instructions = true;
@@ -2513,7 +2530,7 @@ gb_internal void check_asm_template(AsmCtx *asm_ctx, CheckerContext *ctx, Entity
previous_prefix_instr = nullptr;
} else if (res == CheckMnemomic_PseudoMacroMnemonic) {
instr->suffix_flags = suffix_flags;
check_pseudo_macro_mnemonic(asm_ctx, entity, instr, slice_from_array(operands));
all_instructions_good &= check_pseudo_macro_mnemonic(asm_ctx, entity, instr, slice_from_array(operands));
cfg.saw_any_instructions = true;
@@ -2627,6 +2644,7 @@ gb_internal void check_asm_template(AsmCtx *asm_ctx, CheckerContext *ctx, Entity
check_asm_cfg_build(asm_ctx, &cfg, d->init_expr, entity);
check_asm_cfg_analyse(asm_ctx, &cfg, ctx, entity);
check_asm_cfg_liveness(asm_ctx, &cfg, entity, /*emit_dead_writes*/all_instructions_good);
bool vet_unused = false;
{