GCC expands at compile time builtins like __builtin_ffs()
when their argument is constant.
A driver in the kernel uses such a builtin in a case statement,
causing sparse to report:
error: Expected constant expression in case statement
So, let sparse also expand such builtins, somehow like it was
done for bswap16/32/64 but now for ffs/ffsl/ffsll, clz, ctz,
clrsb, popcount & parity.
Reported-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
builtin.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 56 insertions(+)
diff --git a/builtin.c b/builtin.c
index 221c98991..3e2d77e75 100644
--- a/builtin.c
+++ b/builtin.c
@@ -230,6 +230,44 @@ static struct symbol_op bswap_op = {
};
+#define EXPAND_FINDBIT(name) \
+static int expand_##name(struct expression *expr, int cost) \
+{ \
+ struct expression *arg; \
+ long long val; \
+ \
+ if (cost) \
+ return cost; \
+ \
+ arg = first_expression(expr->args); \
+ val = get_expression_value_silent(arg); \
+ switch (expr->ctype->bit_size) { \
+ case sizeof(int) * 8: \
+ val = __builtin_##name(val); break; \
+ case sizeof(long long) * 8: \
+ val = __builtin_##name##ll(val); break; \
+ default: /* impossible error */ \
+ return SIDE_EFFECTS; \
+ } \
+ \
+ expr->value = val; \
+ expr->type = EXPR_VALUE; \
+ expr->taint = 0; \
+ return 0; \
+} \
+ \
+static struct symbol_op name##_op = { \
+ .evaluate = evaluate_pure_unop, \
+ .expand = expand_##name, \
+}
+
+EXPAND_FINDBIT(clz);
+EXPAND_FINDBIT(ctz);
+EXPAND_FINDBIT(clrsb);
+EXPAND_FINDBIT(ffs);
+EXPAND_FINDBIT(parity);
+EXPAND_FINDBIT(popcount);
+
static int evaluate_fp_unop(struct expression *expr)
{
struct expression *arg;
@@ -334,11 +372,29 @@ static struct sym_init {
{ "__builtin_bswap16", &builtin_fn_type, MOD_TOPLEVEL, &bswap_op },
{ "__builtin_bswap32", &builtin_fn_type, MOD_TOPLEVEL, &bswap_op },
{ "__builtin_bswap64", &builtin_fn_type, MOD_TOPLEVEL, &bswap_op },
+ { "__builtin_clrsb", &builtin_fn_type, MOD_TOPLEVEL, &clrsb_op },
+ { "__builtin_clrsbl", &builtin_fn_type, MOD_TOPLEVEL, &clrsb_op },
+ { "__builtin_clrsbll", &builtin_fn_type, MOD_TOPLEVEL, &clrsb_op },
+ { "__builtin_clz", &builtin_fn_type, MOD_TOPLEVEL, &clz_op },
+ { "__builtin_clzl", &builtin_fn_type, MOD_TOPLEVEL, &clz_op },
+ { "__builtin_clzll", &builtin_fn_type, MOD_TOPLEVEL, &clz_op },
+ { "__builtin_ctz", &builtin_fn_type, MOD_TOPLEVEL, &ctz_op },
+ { "__builtin_ctzl", &builtin_fn_type, MOD_TOPLEVEL, &ctz_op },
+ { "__builtin_ctzll", &builtin_fn_type, MOD_TOPLEVEL, &ctz_op },
+ { "__builtin_ffs", &builtin_fn_type, MOD_TOPLEVEL, &ffs_op },
+ { "__builtin_ffsl", &builtin_fn_type, MOD_TOPLEVEL, &ffs_op },
+ { "__builtin_ffsll", &builtin_fn_type, MOD_TOPLEVEL, &ffs_op },
{ "__builtin_isfinite", &builtin_fn_type, MOD_TOPLEVEL, &fp_unop_op },
{ "__builtin_isinf", &builtin_fn_type, MOD_TOPLEVEL, &fp_unop_op },
{ "__builtin_isinf_sign", &builtin_fn_type, MOD_TOPLEVEL, &fp_unop_op },
{ "__builtin_isnan", &builtin_fn_type, MOD_TOPLEVEL, &fp_unop_op },
{ "__builtin_isnormal", &builtin_fn_type, MOD_TOPLEVEL, &fp_unop_op },
+ { "__builtin_parity", &builtin_fn_type, MOD_TOPLEVEL, &parity_op },
+ { "__builtin_parityl", &builtin_fn_type, MOD_TOPLEVEL, &parity_op },
+ { "__builtin_parityll", &builtin_fn_type, MOD_TOPLEVEL, &parity_op },
+ { "__builtin_popcount", &builtin_fn_type, MOD_TOPLEVEL, &popcount_op },
+ { "__builtin_popcountl", &builtin_fn_type, MOD_TOPLEVEL, &popcount_op },
+ { "__builtin_popcountll", &builtin_fn_type, MOD_TOPLEVEL, &popcount_op },
{ "__builtin_signbit", &builtin_fn_type, MOD_TOPLEVEL, &fp_unop_op },
{ "__builtin_add_overflow", &builtin_fn_type, MOD_TOPLEVEL, &overflow_op },
{ "__builtin_sub_overflow", &builtin_fn_type, MOD_TOPLEVEL, &overflow_op },
--
2.23.0
