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asm: minor cleanups

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gingerBill
2026-08-25 13:40:16 +01:00
parent b4cf9b14bd
commit 337bb43948
2 changed files with 67 additions and 53 deletions
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60
src/check_asm.cpp
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@@ -2358,13 +2358,14 @@ gb_internal void check_asm_template(AsmCtx *asm_ctx, CheckerContext *ctx, Entity
entity->type = type;
bool is_volatile = false;
bool is_align_stack = false;
bool is_pure_annotated = false;
auto *clobber_registers_set = &entity->AsmTemplate.clobber_registers_set;
check_asm_specs(asm_ctx, ctx, ate->param_scope, at->specs, &ate->decls);
bool is_pure_annotated = false;
{ // check clobbers
bool is_volatile = false;
bool is_align_stack = false;
auto *clobber_registers_set = &entity->AsmTemplate.clobber_registers_set;
bool clobber_flags = false;
bool clobber_memory = false;
@@ -2432,17 +2433,18 @@ gb_internal void check_asm_template(AsmCtx *asm_ctx, CheckerContext *ctx, Entity
entity->AsmTemplate.clobber_memory = clobber_memory;
entity->AsmTemplate.is_volatile = is_volatile;
entity->AsmTemplate.is_align_stack = is_align_stack;
}
// add normalizations for the reigsters too
for (String const &reg : *clobber_registers_set) {
u16 bit = asm_ctx->clobber_bit_for_reg_name(reg);
String rname = make_string_c(asm_ctx->clobber_reg_bit_name(bit));
if (rname != reg) {
string_set_update(clobber_registers_set, rname);
// add normalizations for the registers too
for (String const &reg : *clobber_registers_set) {
u16 bit = asm_ctx->clobber_bit_for_reg_name(reg);
String rname = make_string_c(asm_ctx->clobber_reg_bit_name(bit));
if (rname != reg) {
string_set_update(clobber_registers_set, rname);
}
}
}
// Two distinct operands pinned to the same physical register only makes sense when
// they are tied (they intentionally share one register). Compared by bit so %eax
// and %rax collide. Flag pins ("flags") yield bit 0 and are skipped.
@@ -2471,16 +2473,6 @@ gb_internal void check_asm_template(AsmCtx *asm_ctx, CheckerContext *ctx, Entity
}
}
// NOTE(bill, 2026-08-24): Construct a control-flow graph (CFG) from the instructions
// to do further analysis which is not possible with an conservative straight-line approximation
// Using a CFG is a much sounder approach for calculating:
// * reads before writes
// * divergence
// * unreachable code
AsmCfg cfg = {};
asm_cfg_init(&cfg);
defer (asm_cfg_destroy(&cfg));
// collect label decls
for (Ast *instruction_ : at->instructions) {
@@ -2507,6 +2499,24 @@ gb_internal void check_asm_template(AsmCtx *asm_ctx, CheckerContext *ctx, Entity
}
}
// NOTE(bill, 2026-08-24): Construct a control-flow graph (CFG) from the instructions
// to do further analysis which is not possible with an conservative straight-line approximation
// Using a CFG is a much sounder approach for calculating:
// * read-before-writes
// * sub-register width checks
// * `%flags` checks
// * divergence
// * unreachable code
// * liveness checks (forward and backwards)
// NOTE(bill): the AsmCfg structure also hold information which is used to in the linear pass
// mainly because it will be used later on by it, so it makes sense to keep them together as
// one unit rather than two separate structures.
AsmCfg cfg = {};
asm_cfg_init(&cfg);
defer (asm_cfg_destroy(&cfg));
Array<Operand> operands = {};
operands.allocator = heap_allocator();
array_reserve(&operands, 16);
@@ -2679,10 +2689,14 @@ gb_internal void check_asm_template(AsmCtx *asm_ctx, CheckerContext *ctx, Entity
error(previous_prefix_instr, "A prefix must be immediately followed by an instruction, but the template ended");
}
// NOTE(bill): After the linear collection pass of the mnemonics,
// now do the CFG building, analysis, and liveness checks (only if everything was correct)
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;
{
AstFile *file = ctx->file;
@@ -2740,7 +2754,7 @@ gb_internal void check_asm_template(AsmCtx *asm_ctx, CheckerContext *ctx, Entity
continue;
}
}
if (ed.tie > 0) {
if (ed.tie >= 0) {
// TODO(bill): Handle this edge case?
continue;
}