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| author | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2018-06-18 10:15:58 +0200 |
|---|---|---|
| committer | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2018-06-23 16:54:50 +0200 |
| commit | 4d851248702bebe6c8ecdd1cef54e7782c72b8a2 (patch) | |
| tree | 0e0fe54d70765a08e945df62b8861314d2ed7af3 /linearize.c | |
| parent | c64d1972a5b775b9d7169dc8db96ee0556af7b26 (diff) | |
| download | sparse-dev-4d851248702bebe6c8ecdd1cef54e7782c72b8a2.tar.gz | |
cast: keep instruction sizes consistent
The last instruction of linearize_load_gen() ensure that
loading a bitfield of size N results in a object of size N.
Also, we require that the usual binops & unops use the same type
on their operand and result. This means that before anything
can be done on the loaded bitfield it must first be sign or zero-
extended in order to match the other operand's size.
The same situation exists when storing a bitfield but there
the extension isn't done. We can thus have some weird code like:
trunc.9 %r2 <- (32) %r1
shl.32 %r3 <- %r2, ...
where a bitfield of size 9 is mixed with a 32 bit shift.
Avoid such mixing of size and always zero extend the bitfield
before storing it (since this was the implicitly desired semantic).
The combination TRUNC + ZEXT can then be optimised later into
a simple masking operation.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Diffstat (limited to 'linearize.c')
| -rw-r--r-- | linearize.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/linearize.c b/linearize.c index d1a079f4..83dfec11 100644 --- a/linearize.c +++ b/linearize.c @@ -26,6 +26,7 @@ static pseudo_t linearize_statement(struct entrypoint *ep, struct statement *stmt); static pseudo_t linearize_expression(struct entrypoint *ep, struct expression *expr); +static pseudo_t add_cast(struct entrypoint *ep, struct symbol *to, struct symbol *from, int op, pseudo_t src); static pseudo_t add_binary_op(struct entrypoint *ep, struct symbol *ctype, int op, pseudo_t left, pseudo_t right); static pseudo_t add_setval(struct entrypoint *ep, struct symbol *ctype, struct expression *val); static pseudo_t linearize_one_symbol(struct entrypoint *ep, struct symbol *sym); @@ -991,8 +992,9 @@ static pseudo_t linearize_store_gen(struct entrypoint *ep, pseudo_t orig = add_load(ep, ad); unsigned long long mask = (1ULL << size) - 1; + store = add_cast(ep, btype, ctype, OP_ZEXT, store); if (shift) { - store = add_binary_op(ep, btype, OP_SHL, value, value_pseudo(shift)); + store = add_binary_op(ep, btype, OP_SHL, store, value_pseudo(shift)); mask <<= shift; } orig = add_binary_op(ep, btype, OP_AND, orig, value_pseudo(~mask)); @@ -1108,6 +1110,14 @@ static pseudo_t add_unop(struct entrypoint *ep, struct symbol *ctype, int op, ps return new; } +static pseudo_t add_cast(struct entrypoint *ep, struct symbol *to, + struct symbol *from, int op, pseudo_t src) +{ + pseudo_t new = add_unop(ep, to, op, src); + new->def->orig_type = from; + return new; +} + static pseudo_t linearize_slice(struct entrypoint *ep, struct expression *expr) { pseudo_t pre = linearize_expression(ep, expr->base); |