Some instruction simplifications can be quite tricky and thus easy to
get wrong. Often, they also are hard to test (for example, you can
test it with a few input values but of course not all combinations).
I'm used to validate some of these with an independent tool
(Alive cfr. [1], [2]) which is quite neat but has some issues:
1) This tool doesn't work with Sparse's IR or C source but it needs to
have the tests written in its own language (very close to LLVM's IR).
So it can be used to test if the logic of a simplification but
not if implemented correctly.
2) This tool isn't maintained anymore (has some bugs too) and it's
successor (Alive2 [3]) is not quite as handy to me (I miss the
pre-conditions a lot).
So, this patch implement the same idea but fully integrated with
Sparse. This mean that you can write a test in C, let Sparse process
and simplify it and then directly validate it and not only for
a few values but symbolically, for all possible values.
Note: Of course, this is not totally stand-alone and depends on
an external library for the solver (Boolector, see [4], [5]).
Note: Currently, it's just a proof of concept and, except the
included tests, it's only very slightly tested (and untested
with anything more complex than a few instructions).
[1] https://blog.regehr.org/archives/1170
[2] https://www.cs.utah.edu/~regehr/papers/pldi15.pdf
[3] https://blog.regehr.org/archives/1722
[4] https://boolector.github.io/
[5] https://boolector.github.io/papers/BrummayerBiere-TACAS09.pdf
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
.gitignore | 1 +
Makefile | 7 +
ident-list.h | 3 +
scheck.c | 302 +++++++++++++++++++++++++++++++++++++++++
validation/scheck/ko.c | 10 ++
validation/scheck/ok.c | 14 ++
validation/test-suite | 6 +
7 files changed, 343 insertions(+)
create mode 100644 scheck.c
create mode 100644 validation/scheck/ko.c
create mode 100644 validation/scheck/ok.c
diff --git a/.gitignore b/.gitignore
index 6a28fa50f8bb..b22f86b1ddfb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,6 +17,7 @@
/example
/graph
/obfuscate
+/scheck
/semind
/sparse
/sparse-llvm
diff --git a/Makefile b/Makefile
index f9883da101c7..a0178a65a11a 100644
--- a/Makefile
+++ b/Makefile
@@ -227,6 +227,13 @@ else
$(warning Your system does not have llvm, disabling sparse-llvm)
endif
+ifeq ($(HAVE_BOOLECTOR),yes)
+PROGRAMS += scheck
+scheck-cflags := -I${BOOLECTORDIR}/include/boolector
+scheck-ldflags := -L${BOOLECTORDIR}/lib
+scheck-ldlibs := -lboolector -llgl -lbtor2parser
+endif
+
########################################################################
LIBS := libsparse.a
OBJS := $(LIB_OBJS) $(EXTRA_OBJS) $(PROGRAMS:%=%.o)
diff --git a/ident-list.h b/ident-list.h
index 8049b6940745..918f54d75fc4 100644
--- a/ident-list.h
+++ b/ident-list.h
@@ -78,6 +78,9 @@ IDENT(memset); IDENT(memcpy);
IDENT(copy_to_user); IDENT(copy_from_user);
IDENT(main);
+/* used by the symbolic checker */
+IDENT(__assert);
+
#undef __IDENT
#undef IDENT
#undef IDENT_RESERVED
diff --git a/scheck.c b/scheck.c
new file mode 100644
index 000000000000..719aeea84e7c
--- /dev/null
+++ b/scheck.c
@@ -0,0 +1,302 @@
+// SPDX-License-Identifier: MIT
+// Copyright (C) 2021 Luc Van Oostenryck
+
+///
+// Symbolic checker for Sparse's IR
+// --------------------------------
+//
+// This is an example client program with a dual purpose:
+// # It shows how to translate Sparse's IR into the language
+// of SMT solvers (only the part concerning integers,
+// floating-point and memory is ignored).
+// # It's used as a simple symbolic checker for the IR.
+// The idea is to create a mini-language that allows to
+// express some assertions with some pre-conditions.
+
+#include <stdarg.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <ctype.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#include <boolector.h>
+#include "lib.h"
+#include "expression.h"
+#include "linearize.h"
+#include "symbol.h"
+#include "builtin.h"
+
+
+#define dyntype incomplete_ctype
+static const struct builtin_fn builtins_scheck[] = {
+ { "__assert", &void_ctype, 0, { &bool_ctype }, .op = &generic_int_op },
+ {}
+};
+
+
+static BoolectorSort get_sort(Btor *btor, struct symbol *type, struct position pos)
+{
+ if (!is_int_type(type)) {
+ sparse_error(pos, "invalid type");
+ return NULL;
+ }
+ return boolector_bitvec_sort(btor, type->bit_size);
+}
+
+static BoolectorNode *mkvar(Btor *btor, BoolectorSort s, pseudo_t pseudo)
+{
+ static char buff[33];
+ BoolectorNode *n;
+
+ if (pseudo->priv)
+ return pseudo->priv;
+
+ switch (pseudo->type) {
+ case PSEUDO_VAL:
+ sprintf(buff, "%llx", pseudo->value);
+ return boolector_consth(btor, s, buff);
+ case PSEUDO_ARG:
+ case PSEUDO_REG:
+ n = boolector_var(btor, s, show_pseudo(pseudo));
+ break;
+ default:
+ fprintf(stderr, "invalid pseudo: %s\n", show_pseudo(pseudo));
+ return NULL;
+ }
+ return pseudo->priv = n;
+}
+
+static BoolectorNode *get_arg(Btor *btor, struct instruction *insn, int idx)
+{
+ pseudo_t arg = ptr_list_nth(insn->arguments, idx);
+ struct symbol *type = ptr_list_nth(insn->fntypes, idx + 1);
+ BoolectorSort s = get_sort(btor, type, insn->pos);
+
+ return mkvar(btor, s, arg);
+}
+
+static BoolectorNode *zext(Btor *btor, struct instruction *insn, BoolectorNode *s)
+{
+ int old = boolector_get_width(btor, s);
+ int new = insn->type->bit_size;
+ return boolector_uext(btor, s, new - old);
+}
+
+static BoolectorNode *sext(Btor *btor, struct instruction *insn, BoolectorNode *s)
+{
+ int old = boolector_get_width(btor, s);
+ int new = insn->type->bit_size;
+ return boolector_sext(btor, s, new - old);
+}
+
+static BoolectorNode *slice(Btor *btor, struct instruction *insn, BoolectorNode *s)
+{
+ int old = boolector_get_width(btor, s);
+ int new = insn->type->bit_size;
+ return boolector_slice(btor, s, old - new - 1, 0);
+}
+
+static void binop(Btor *btor, struct instruction *insn)
+{
+ BoolectorSort s = get_sort(btor, insn->type, insn->pos);
+ BoolectorNode *t, *a, *b;
+
+ a = mkvar(btor, s, insn->src1);
+ b = mkvar(btor, s, insn->src2);
+ if (!a || !b)
+ return;
+ switch (insn->opcode) {
+ case OP_ADD: t = boolector_add(btor, a, b); break;
+ case OP_SUB: t = boolector_sub(btor, a, b); break;
+ case OP_MUL: t = boolector_mul(btor, a, b); break;
+ case OP_AND: t = boolector_and(btor, a, b); break;
+ case OP_OR: t = boolector_or (btor, a, b); break;
+ case OP_XOR: t = boolector_xor(btor, a, b); break;
+ case OP_SHL: t = boolector_sll(btor, a, b); break;
+ case OP_LSR: t = boolector_srl(btor, a, b); break;
+ case OP_ASR: t = boolector_sra(btor, a, b); break;
+ case OP_DIVS: t = boolector_sdiv(btor, a, b); break;
+ case OP_DIVU: t = boolector_udiv(btor, a, b); break;
+ case OP_MODS: t = boolector_srem(btor, a, b); break;
+ case OP_MODU: t = boolector_urem(btor, a, b); break;
+ case OP_SET_EQ: t = zext(btor, insn, boolector_eq(btor, a, b)); break;
+ case OP_SET_NE: t = zext(btor, insn, boolector_ne(btor, a, b)); break;
+ case OP_SET_LT: t = zext(btor, insn, boolector_slt(btor, a, b)); break;
+ case OP_SET_LE: t = zext(btor, insn, boolector_slte(btor, a, b)); break;
+ case OP_SET_GE: t = zext(btor, insn, boolector_sgte(btor, a, b)); break;
+ case OP_SET_GT: t = zext(btor, insn, boolector_sgt(btor, a, b)); break;
+ case OP_SET_B: t = zext(btor, insn, boolector_ult(btor, a, b)); break;
+ case OP_SET_BE: t = zext(btor, insn, boolector_ulte(btor, a, b)); break;
+ case OP_SET_AE: t = zext(btor, insn, boolector_ugte(btor, a, b)); break;
+ case OP_SET_A: t = zext(btor, insn, boolector_ugt(btor, a, b)); break;
+ default:
+ fprintf(stderr, "unsupported insn\n");
+ return;
+ }
+ insn->target->priv = t;
+}
+
+static void unop(Btor *btor, struct instruction *insn)
+{
+ BoolectorSort s = get_sort(btor, insn->type, insn->pos);
+ BoolectorNode *t, *a;
+
+ a = mkvar(btor, s, insn->src1);
+ if (!a)
+ return;
+ switch (insn->opcode) {
+ case OP_NEG: t = boolector_neg(btor, a); break;
+ case OP_NOT: t = boolector_not(btor, a); break;
+ case OP_SEXT: t = sext(btor, insn, a); break;
+ case OP_ZEXT: t = zext(btor, insn, a); break;
+ case OP_TRUNC: t = slice(btor, insn, a); break;
+ default:
+ fprintf(stderr, "unsupported insn\n");
+ return;
+ }
+ insn->target->priv = t;
+}
+
+static void ternop(Btor *btor, struct instruction *insn)
+{
+ BoolectorSort s = get_sort(btor, insn->type, insn->pos);
+ BoolectorNode *t, *a, *b, *c, *z, *d;
+
+ a = mkvar(btor, s, insn->src1);
+ b = mkvar(btor, s, insn->src2);
+ c = mkvar(btor, s, insn->src3);
+ if (!a || !b || !c)
+ return;
+ switch (insn->opcode) {
+ case OP_SEL:
+ z = boolector_zero(btor, s);
+ d = boolector_ne(btor, a, z);
+ t = boolector_cond(btor, d, b, c);
+ break;
+ default:
+ fprintf(stderr, "unsupported insn\n");
+ return;
+ }
+ insn->target->priv = t;
+}
+
+static bool check_btor(Btor *btor, BoolectorNode *n, struct instruction *insn)
+{
+ char model_format[] = "btor";
+ int res;
+
+ boolector_assert(btor, boolector_not(btor, n));
+ res = boolector_sat(btor);
+ switch (res) {
+ case BOOLECTOR_UNSAT:
+ return 1;
+ case BOOLECTOR_SAT:
+ sparse_error(insn->pos, "assertion failed");
+ show_entry(insn->bb->ep);
+ boolector_dump_btor(btor, stdout);
+ boolector_print_model(btor, model_format, stdout);
+ break;
+ default:
+ sparse_error(insn->pos, "SMT failure");
+ break;
+ }
+ return 0;
+}
+
+static bool check_assert(Btor *btor, struct instruction *insn)
+{
+ BoolectorNode *a = get_arg(btor, insn, 0);
+ BoolectorNode *z = boolector_zero(btor, boolector_get_sort(btor, a));
+ BoolectorNode *n = boolector_ne(btor, a, z);
+ return check_btor(btor, n, insn);
+}
+
+static bool check_call(Btor *btor, struct instruction *insn)
+{
+ pseudo_t func = insn->func;
+ struct ident *ident = func->ident;
+
+ if (ident == &__assert_ident)
+ return check_assert(btor, insn);
+ return 0;
+}
+
+static bool check_function(struct entrypoint *ep)
+{
+ Btor *btor = boolector_new();
+ struct basic_block *bb;
+ int rc = 0;
+
+ boolector_set_opt(btor, BTOR_OPT_MODEL_GEN, 1);
+
+ FOR_EACH_PTR(ep->bbs, bb) {
+ struct instruction *insn;
+ FOR_EACH_PTR(bb->insns, insn) {
+ if (!insn->bb)
+ continue;
+ switch (insn->opcode) {
+ case OP_ENTRY:
+ continue;
+ case OP_BINARY ... OP_BINARY_END:
+ case OP_BINCMP ... OP_BINCMP_END:
+ binop(btor, insn);
+ break;
+ case OP_UNOP ... OP_UNOP_END:
+ unop(btor, insn);
+ break;
+ case OP_SEL:
+ ternop(btor, insn);
+ break;
+ case OP_CALL:
+ rc = check_call(btor, insn);
+ goto out;
+ case OP_RET:
+ goto out;
+ default:
+ fprintf(stderr, "unsupported insn\n");
+ goto out;
+ }
+ } END_FOR_EACH_PTR(insn);
+ } END_FOR_EACH_PTR(bb);
+ fprintf(stderr, "unterminated function\n");
+
+out:
+ boolector_release_all(btor);
+ boolector_delete(btor);
+ return rc;
+}
+
+static void check_functions(struct symbol_list *list)
+{
+ struct symbol *sym;
+
+ FOR_EACH_PTR(list, sym) {
+ struct entrypoint *ep;
+
+ expand_symbol(sym);
+ ep = linearize_symbol(sym);
+ if (!ep || !ep->entry)
+ continue;
+ check_function(ep);
+ } END_FOR_EACH_PTR(sym);
+}
+
+int main(int argc, char **argv)
+{
+ struct string_list *filelist = NULL;
+ char *file;
+
+ Wdecl = 0;
+
+ sparse_initialize(argc, argv, &filelist);
+
+ declare_builtins(0, builtins_scheck);
+
+ // Expand, linearize and check.
+ FOR_EACH_PTR(filelist, file) {
+ check_functions(sparse(file));
+ } END_FOR_EACH_PTR(file);
+ return 0;
+}
diff --git a/validation/scheck/ko.c b/validation/scheck/ko.c
new file mode 100644
index 000000000000..dbd861ea17fd
--- /dev/null
+++ b/validation/scheck/ko.c
@@ -0,0 +1,10 @@
+static void ko(int x)
+{
+ __assert((~x) == (~0 + x));
+}
+
+/*
+ * check-name: scheck-ko
+ * check-command: scheck $file
+ * check-known-to-fail
+ */
diff --git a/validation/scheck/ok.c b/validation/scheck/ok.c
new file mode 100644
index 000000000000..113912e01aad
--- /dev/null
+++ b/validation/scheck/ok.c
@@ -0,0 +1,14 @@
+static void ok(int x)
+{
+ __assert((~x) == (~0 - x)); // true but not simplified yet
+}
+
+static void always(int x)
+{
+ __assert((x - x) == 0); // true and simplified
+}
+
+/*
+ * check-name: scheck-ok
+ * check-command: scheck $file
+ */
diff --git a/validation/test-suite b/validation/test-suite
index 1b05c75e9f74..2f7950ef50a4 100755
--- a/validation/test-suite
+++ b/validation/test-suite
@@ -13,6 +13,9 @@ prog_name=`basename $0`
if [ ! -x "$default_path/sparse-llvm" ]; then
disabled_cmds="sparsec sparsei sparse-llvm sparse-llvm-dis"
fi
+if [ ! -x "$default_path/scheck" ]; then
+ disabled_cmds="$disabled_cmds scheck"
+fi
# flags:
# - some tests gave an unexpected result
@@ -513,6 +516,7 @@ echo " -a append the created test to the input file"
echo " -f write a test known to fail"
echo " -l write a test for linearized code"
echo " -p write a test for pre-processing"
+echo " -s write a test for symbolic checking"
echo
echo "argument(s):"
echo " file file containing the test case(s)"
@@ -540,6 +544,8 @@ do_format()
linear=1 ;;
-p)
def_cmd='sparse -E $file' ;;
+ -s)
+ def_cmd='scheck $file' ;;
help|-*)
do_format_help
--
2.31.1
