commit fc135991fcc5ebe9905cbba92a8727c4fb4983fe
parent 742334caf508bb498f86dac5f9d426b78024d4e0
Author: Drew DeVault <sir@cmpwn.com>
Date: Tue, 10 Aug 2021 11:04:55 +0200
gen: implement efficient path for slice alloc
This adds a more efficient path when initializing slices from arrays
which allows them to be generated with _at semantics on the allocated
storage area, rather than with a copy.
This also fixes an issue with freeing slices.
Signed-off-by: Drew DeVault <sir@cmpwn.com>
Diffstat:
2 files changed, 25 insertions(+), 25 deletions(-)
diff --git a/src/gen.c b/src/gen.c
@@ -366,42 +366,31 @@ gen_alloc_slice_at(struct gen_context *ctx,
const struct expression *expr,
struct gen_value out)
{
- // TODO: We should avoid an extra allocation for some array cases if we
- // wrote a separate code-path which allocates first (using the array
- // length, which is known at compile time) and then uses gen_expr_at to
- // initialize directly into the new storage area.
- //
- // This will likely be very important if we start working with
- // initializers for arrays of a large size, e.g.
- //
- // let x: [4096]int = alloc([0...]);
- //
- // The current approach will cause the [4096]int initializer to be
- // stack-allocated and copied into the new allocated space.
struct qbe_value qcap;
if (expr->alloc.cap) {
struct gen_value cap = gen_expr(ctx, expr->alloc.cap);
qcap = mkqval(ctx, &cap);
}
- struct gen_value init = gen_expr(ctx, expr->alloc.expr);
- struct qbe_value qinit = mkqval(ctx, &init);
-
+ struct gen_value init;
+ struct qbe_value qinit;
struct qbe_value length, initdata;
const struct type *inittype = type_dealias(expr->alloc.expr->result);
switch (inittype->storage) {
case STORAGE_ARRAY:
assert(inittype->array.length != SIZE_UNDEFINED);
length = constl(inittype->array.length);
- initdata = mkqval(ctx, &init);
break;
- case STORAGE_SLICE:;
+ case STORAGE_SLICE:
+ init = gen_expr(ctx, expr->alloc.expr);
+ qinit = mkqval(ctx, &init);
enum qbe_instr load = load_for_type(ctx, &builtin_type_size);
initdata = mkqtmp(ctx, ctx->arch.ptr, ".%d");
pushi(ctx->current, &initdata, load, &qinit, NULL);
struct qbe_value offset = constl(builtin_type_size.size);
struct qbe_value ptr = mkqtmp(ctx, ctx->arch.ptr, ".%d");
pushi(ctx->current, &ptr, Q_ADD, &qinit, &offset, NULL);
+ length = mkqtmp(ctx, ctx->arch.sz, ".%d");
pushi(ctx->current, &length, load, &ptr, NULL);
break;
default: abort(); // Invariant
@@ -446,8 +435,18 @@ gen_alloc_slice_at(struct gen_context *ctx,
pushi(ctx->current, &ptr, Q_ADD, &base, &offset, NULL);
pushi(ctx->current, NULL, store, &qcap, &ptr, NULL);
- struct qbe_value rtmemcpy = mkrtfunc(ctx, "rt.memcpy");
- pushi(ctx->current, NULL, Q_CALL, &rtmemcpy, &data, &initdata, &size, NULL);
+ if (inittype->storage == STORAGE_ARRAY) {
+ struct gen_value storage = (struct gen_value){
+ .kind = GV_TEMP,
+ .type = inittype,
+ .name = data.name,
+ };
+ gen_expr_at(ctx, expr->alloc.expr, storage);
+ } else {
+ struct qbe_value rtmemcpy = mkrtfunc(ctx, "rt.memcpy");
+ pushi(ctx->current, NULL, Q_CALL, &rtmemcpy,
+ &data, &initdata, &size, NULL);
+ }
}
static struct gen_value
@@ -1323,13 +1322,14 @@ static struct gen_value
gen_expr_free(struct gen_context *ctx, const struct expression *expr)
{
const struct type *type = type_dealias(expr->alloc.expr->result);
- struct gen_value val = gen_expr(ctx, expr->alloc.expr);
- if (type->storage == STORAGE_SLICE
- || type->storage == STORAGE_STRING) {
- val = gen_load(ctx, val);
- }
struct qbe_value rtfunc = mkrtfunc(ctx, "rt.free");
+ struct gen_value val = gen_expr(ctx, expr->alloc.expr);
struct qbe_value qval = mkqval(ctx, &val);
+ if (type->storage == STORAGE_SLICE || type->storage == STORAGE_STRING) {
+ struct qbe_value lval = mklval(ctx, &val);
+ qval = mkqtmp(ctx, ctx->arch.ptr, ".%d");
+ pushi(ctx->current, &qval, Q_LOADL, &lval, NULL);
+ }
pushi(ctx->current, NULL, Q_CALL, &rtfunc, &qval, NULL);
return gv_void;
}
diff --git a/tests/configure b/tests/configure
@@ -77,7 +77,7 @@ tests/$t: libhart.a tests/$t.ha
@printf 'HAREC\t%s\t$@\n' "tests/$t"
@HARECACHE=\$(HARECACHE) ./harec -o tests/$t.ssa tests/$t.ha
@\$(QBE) -o tests/$t.s tests/$t.ssa
- @\$(AS) -o tests/$t.o tests/$t.s
+ @\$(AS) -g -o tests/$t.o tests/$t.s
@\$(LD) --gc-sections -T rt/hare.sc -o tests/$t $rtstart tests/$t.o libhart.a
@rm tests/$t.s tests/$t.ssa tests/$t.o
