Re: Add support to trace comparison instructions and switch statements

["吴潍浠(此彼)" <weixi.wwx@antfin.com>]

Hi Jakub
I compiled libjpeg-turbo and libdng_sdk with options "-g -O3 -Wall -fsanitize-coverage=trace-pc,trace-cmp -fsanitize=address".
And run my fuzzer with pc and cmp feedbacks for hours. It works fine.
About __sanitizer_cov_trace_cmp{f,d} , yes, it  isn't provided by llvm. But once we trace integer comparisons, why not real type comparisons.
I remember Dmitry said it is not enough useful to trace real type comparisons because it is rare to see them in programs.
But libdng_sdk really has real type comparisons. So I want to keep them and implementing __sanitizer_cov_trace_const_cmp{f,d} may be necessary.

And thanks again for your professional help.

Wish Wu

------------------------------------------------------------------
From:Jakub Jelinek <jakub@redhat.com>
Time:2017 Sep 6 (Wed) 05:44
To:Wish Wu <weixi.wwx@antfin.com>
Cc:Dmitry Vyukov <dvyukov@google.com>; gcc-patches <gcc-patches@gcc.gnu.org>; Jeff Law <law@redhat.com>; wishwu007 <wishwu007@gmail.com>
Subject:Re: Add support to trace comparison instructions and switch statements


On Tue, Sep 05, 2017 at 09:03:52PM +0800, 吴潍浠(此彼) wrote:
> Attachment is my updated path.
> The implementation of parse_sanitizer_options is not elegance enough. Mixing handling flags of fsanitize is easy to make mistakes.

To avoid too many further iterations, I took the liberty to tweak your
patch.  From https://clang.llvm.org/docs/SanitizerCoverage.html
I've noticed that since 2017-08-11 clang/llvm wants to emit
__sanitizer_cov_trace_const_cmpN with the first argument a constant
if one of the comparison operands is a constant, so the patch implements
that too.
I wonder about the __sanitizer_cov_trace_cmp{f,d} entry-points, because
I can't find them on that page nor in llvm sources.
I've also added handling of COND_EXPRs and added some documentation.

I've bootstrapped/regtested the patch on x86_64-linux and i686-linux.
Can you test it on whatever you want to use the patch for?

2017-09-05  Wish Wu  <wishwu007@gmail.com>
     Jakub Jelinek  <jakub@redhat.com>

 * asan.c (initialize_sanitizer_builtins): Add
 BT_FN_VOID_UINT8_UINT8, BT_FN_VOID_UINT16_UINT16,
 BT_FN_VOID_UINT32_UINT32, BT_FN_VOID_UINT64_UINT64,
 BT_FN_VOID_FLOAT_FLOAT, BT_FN_VOID_DOUBLE_DOUBLE and
 BT_FN_VOID_UINT64_PTR variables.
 * builtin-types.def (BT_FN_VOID_UINT8_UINT8): New fn type.
 (BT_FN_VOID_UINT16_UINT16): Likewise.
 (BT_FN_VOID_UINT32_UINT32): Likewise.
 (BT_FN_VOID_FLOAT_FLOAT): Likewise.
 (BT_FN_VOID_DOUBLE_DOUBLE): Likewise.
 (BT_FN_VOID_UINT64_PTR): Likewise.
 * common.opt (flag_sanitize_coverage): New variable.
 (fsanitize-coverage=trace-pc): Remove.
 (fsanitize-coverage=): Add.
 * flag-types.h (enum sanitize_coverage_code): New enum.
 * fold-const.c (fold_range_test): Disable non-short-circuit
 optimization if flag_sanitize_coverage.
 (fold_truth_andor): Likewise.
 * tree-ssa-ifcombine.c (ifcombine_ifandif): Likewise.
 * opts.c (COVERAGE_SANITIZER_OPT): Define.
 (coverage_sanitizer_opts): New array.
 (get_closest_sanitizer_option): Add OPTS argument, handle also
 OPT_fsanitize_coverage_.
 (parse_sanitizer_options): Adjusted to also handle
 OPT_fsanitize_coverage_.
 (common_handle_option): Add OPT_fsanitize_coverage_.
 * sancov.c (instrument_comparison, instrument_switch): New function.
 (sancov_pass): Add trace-cmp support.
 * sanitizer.def (BUILT_IN_SANITIZER_COV_TRACE_CMP1,
 BUILT_IN_SANITIZER_COV_TRACE_CMP2, BUILT_IN_SANITIZER_COV_TRACE_CMP4,
 BUILT_IN_SANITIZER_COV_TRACE_CMP8,
 BUILT_IN_SANITIZER_COV_TRACE_CONST_CMP1,
 BUILT_IN_SANITIZER_COV_TRACE_CONST_CMP2,
 BUILT_IN_SANITIZER_COV_TRACE_CONST_CMP4,
 BUILT_IN_SANITIZER_COV_TRACE_CONST_CMP8,
 BUILT_IN_SANITIZER_COV_TRACE_CMPF, BUILT_IN_SANITIZER_COV_TRACE_CMPD,
 BUILT_IN_SANITIZER_COV_TRACE_SWITCH): New builtins.
 * doc/invoke.texi: Document -fsanitize-coverage=trace-cmp.

 * gcc.dg/sancov/cmp0.c: New test.

--- gcc/asan.c.jj 2017-09-04 09:55:26.600687479 +0200
+++ gcc/asan.c 2017-09-05 15:39:32.452612728 +0200
@@ -2709,6 +2709,29 @@ initialize_sanitizer_builtins (void)
   tree BT_FN_SIZE_CONST_PTR_INT
     = build_function_type_list (size_type_node, const_ptr_type_node,
     integer_type_node, NULL_TREE);
+
+  tree BT_FN_VOID_UINT8_UINT8
+    = build_function_type_list (void_type_node, unsigned_char_type_node,
+    unsigned_char_type_node, NULL_TREE);
+  tree BT_FN_VOID_UINT16_UINT16
+    = build_function_type_list (void_type_node, uint16_type_node,
+    uint16_type_node, NULL_TREE);
+  tree BT_FN_VOID_UINT32_UINT32
+    = build_function_type_list (void_type_node, uint32_type_node,
+    uint32_type_node, NULL_TREE);
+  tree BT_FN_VOID_UINT64_UINT64
+    = build_function_type_list (void_type_node, uint64_type_node,
+    uint64_type_node, NULL_TREE);
+  tree BT_FN_VOID_FLOAT_FLOAT
+    = build_function_type_list (void_type_node, float_type_node,
+    float_type_node, NULL_TREE);
+  tree BT_FN_VOID_DOUBLE_DOUBLE
+    = build_function_type_list (void_type_node, double_type_node,
+    double_type_node, NULL_TREE);
+  tree BT_FN_VOID_UINT64_PTR
+    = build_function_type_list (void_type_node, uint64_type_node,
+    ptr_type_node, NULL_TREE);
+
   tree BT_FN_BOOL_VPTR_PTR_IX_INT_INT[5];
   tree BT_FN_IX_CONST_VPTR_INT[5];
   tree BT_FN_IX_VPTR_IX_INT[5];
--- gcc/builtin-types.def.jj 2017-06-28 09:05:45.249396972 +0200
+++ gcc/builtin-types.def 2017-09-05 15:39:32.453612716 +0200
@@ -338,8 +338,20 @@ DEF_FUNCTION_TYPE_2 (BT_FN_VOID_PTRMODE_
        BT_VOID, BT_PTRMODE, BT_PTR)
 DEF_FUNCTION_TYPE_2 (BT_FN_VOID_PTR_PTRMODE,
        BT_VOID, BT_PTR, BT_PTRMODE)
+DEF_FUNCTION_TYPE_2 (BT_FN_VOID_UINT8_UINT8,
+            BT_VOID, BT_UINT8, BT_UINT8)
+DEF_FUNCTION_TYPE_2 (BT_FN_VOID_UINT16_UINT16,
+            BT_VOID, BT_UINT16, BT_UINT16)
+DEF_FUNCTION_TYPE_2 (BT_FN_VOID_UINT32_UINT32,
+            BT_VOID, BT_UINT32, BT_UINT32)
 DEF_FUNCTION_TYPE_2 (BT_FN_VOID_UINT64_UINT64,
             BT_VOID, BT_UINT64, BT_UINT64)
+DEF_FUNCTION_TYPE_2 (BT_FN_VOID_FLOAT_FLOAT,
+            BT_VOID, BT_FLOAT, BT_FLOAT)
+DEF_FUNCTION_TYPE_2 (BT_FN_VOID_DOUBLE_DOUBLE,
+            BT_VOID, BT_DOUBLE, BT_DOUBLE)
+DEF_FUNCTION_TYPE_2 (BT_FN_VOID_UINT64_PTR,
+            BT_VOID, BT_UINT64, BT_PTR)
 DEF_FUNCTION_TYPE_2 (BT_FN_VOID_VALIST_REF_VALIST_ARG,
        BT_VOID, BT_VALIST_REF, BT_VALIST_ARG)
 DEF_FUNCTION_TYPE_2 (BT_FN_LONG_LONG_LONG,
--- gcc/common.opt.jj 2017-09-01 09:26:48.441614145 +0200
+++ gcc/common.opt 2017-09-05 15:39:32.454612704 +0200
@@ -233,10 +233,9 @@ unsigned int flag_sanitize
 Variable
 unsigned int flag_sanitize_recover = (SANITIZE_UNDEFINED | SANITIZE_UNDEFINED_NONDEFAULT | SANITIZE_KERNEL_ADDRESS) & ~(SANITIZE_UNREACHABLE | SANITIZE_RETURN)
 
-fsanitize-coverage=trace-pc
-Common Report Var(flag_sanitize_coverage)
-Enable coverage-guided fuzzing code instrumentation.
-Inserts call to __sanitizer_cov_trace_pc into every basic block.
+; What the coverage sanitizers should instrument
+Variable
+unsigned int flag_sanitize_coverage
 
 ; Flag whether a prefix has been added to dump_base_name
 Variable
@@ -982,6 +981,10 @@ fsanitize=
 Common Driver Report Joined
 Select what to sanitize.
 
+fsanitize-coverage=
+Common Report Joined
+Select what to coverage sanitize.
+
 fasan-shadow-offset=
 Common Joined RejectNegative Var(common_deferred_options) Defer
 -fasan-shadow-offset=<number> Use custom shadow memory offset.
--- gcc/flag-types.h.jj 2017-07-28 12:35:27.562412268 +0200
+++ gcc/flag-types.h 2017-09-05 15:39:32.454612704 +0200
@@ -252,6 +252,14 @@ enum sanitize_code {
       | SANITIZE_BOUNDS_STRICT
 };
 
+/* Different trace modes.  */
+enum sanitize_coverage_code {
+  /* Trace PC.  */
+  SANITIZE_COV_TRACE_PC = 1 << 0,
+  /* Trace Comparison.  */
+  SANITIZE_COV_TRACE_CMP = 1 << 1
+};
+
 /* flag_vtable_verify initialization levels. */
 enum vtv_priority {
   VTV_NO_PRIORITY       = 0,  /* i.E. Do NOT do vtable verification. */
--- gcc/fold-const.c.jj 2017-09-01 09:25:46.275345134 +0200
+++ gcc/fold-const.c 2017-09-05 15:39:32.457612668 +0200
@@ -5394,6 +5394,7 @@ fold_range_test (location_t loc, enum tr
      short-circuited branch and the underlying object on both sides
      is the same, make a non-short-circuit operation.  */
   else if (LOGICAL_OP_NON_SHORT_CIRCUIT
+    && !flag_sanitize_coverage
     && lhs != 0 && rhs != 0
     && (code == TRUTH_ANDIF_EXPR
         || code == TRUTH_ORIF_EXPR)
@@ -8035,6 +8036,7 @@ fold_truth_andor (location_t loc, enum t
     return tem;
 
   if (LOGICAL_OP_NON_SHORT_CIRCUIT
+      && !flag_sanitize_coverage
       && (code == TRUTH_AND_EXPR
           || code == TRUTH_ANDIF_EXPR
           || code == TRUTH_OR_EXPR
--- gcc/opts.c.jj 2017-09-01 09:26:28.041854018 +0200
+++ gcc/opts.c 2017-09-05 15:53:18.752765907 +0200
@@ -1526,6 +1526,17 @@ const struct sanitizer_opts_s sanitizer_
   { NULL, 0U, 0UL, false }
 };
 
+/* -f{,no-}sanitize-coverage= suboptions.  */
+const struct sanitizer_opts_s coverage_sanitizer_opts[] =
+{
+#define COVERAGE_SANITIZER_OPT(name, flags) \
+    { #name, flags, sizeof #name - 1, true }
+  COVERAGE_SANITIZER_OPT (trace-pc, SANITIZE_COV_TRACE_PC),
+  COVERAGE_SANITIZER_OPT (trace-cmp, SANITIZE_COV_TRACE_CMP),
+#undef COVERAGE_SANITIZER_OPT
+  { NULL, 0U, 0UL, false }
+};
+
 /* A struct for describing a run of chars within a string.  */
 
 struct string_fragment
@@ -1556,31 +1567,34 @@ struct edit_distance_traits<const string
 
 /* Given ARG, an unrecognized sanitizer option, return the best
    matching sanitizer option, or NULL if there isn't one.
-   CODE is OPT_fsanitize_ or OPT_fsanitize_recover_.
+   OPTS is array of candidate sanitizer options.
+   CODE is OPT_fsanitize_, OPT_fsanitize_recover_ or
+   OPT_fsanitize_coverage_.
    VALUE is non-zero for the regular form of the option, zero
    for the "no-" form (e.g. "-fno-sanitize-recover=").  */
 
 static const char *
 get_closest_sanitizer_option (const string_fragment &arg,
+         const struct sanitizer_opts_s *opts,
          enum opt_code code, int value)
 {
   best_match <const string_fragment &, const char*> bm (arg);
-  for (int i = 0; sanitizer_opts[i].name != NULL; ++i)
+  for (int i = 0; opts[i].name != NULL; ++i)
     {
       /* -fsanitize=all is not valid, so don't offer it.  */
-      if (sanitizer_opts[i].flag == ~0U
-   && code == OPT_fsanitize_
+      if (code == OPT_fsanitize_
+   && opts[i].flag == ~0U
    && value)
  continue;
 
       /* For -fsanitize-recover= (and not -fno-sanitize-recover=),
   don't offer the non-recoverable options.  */
-      if (!sanitizer_opts[i].can_recover
-   && code == OPT_fsanitize_recover_
+      if (code == OPT_fsanitize_recover_
+   && !opts[i].can_recover
    && value)
  continue;
 
-      bm.consider (sanitizer_opts[i].name);
+      bm.consider (opts[i].name);
     }
   return bm.get_best_meaningful_candidate ();
 }
@@ -1594,6 +1608,13 @@ parse_sanitizer_options (const char *p,
     unsigned int flags, int value, bool complain)
 {
   enum opt_code code = (enum opt_code) scode;
+
+  const struct sanitizer_opts_s *opts;
+  if (code == OPT_fsanitize_coverage_)
+    opts = coverage_sanitizer_opts;
+  else
+    opts = sanitizer_opts;
+
   while (*p != 0)
     {
       size_t len, i;
@@ -1611,12 +1632,11 @@ parse_sanitizer_options (const char *p,
  }
 
       /* Check to see if the string matches an option class name.  */
-      for (i = 0; sanitizer_opts[i].name != NULL; ++i)
- if (len == sanitizer_opts[i].len
-     && memcmp (p, sanitizer_opts[i].name, len) == 0)
+      for (i = 0; opts[i].name != NULL; ++i)
+ if (len == opts[i].len && memcmp (p, opts[i].name, len) == 0)
    {
      /* Handle both -fsanitize and -fno-sanitize cases.  */
-     if (value && sanitizer_opts[i].flag == ~0U)
+     if (value && opts[i].flag == ~0U)
        {
   if (code == OPT_fsanitize_)
     {
@@ -1633,14 +1653,14 @@ parse_sanitizer_options (const char *p,
      -fsanitize-recover=return if -fsanitize-recover=undefined
      is selected.  */
   if (code == OPT_fsanitize_recover_
-      && sanitizer_opts[i].flag == SANITIZE_UNDEFINED)
+      && opts[i].flag == SANITIZE_UNDEFINED)
     flags |= (SANITIZE_UNDEFINED
        & ~(SANITIZE_UNREACHABLE | SANITIZE_RETURN));
   else
-    flags |= sanitizer_opts[i].flag;
+    flags |= opts[i].flag;
        }
      else
-       flags &= ~sanitizer_opts[i].flag;
+       flags &= ~opts[i].flag;
      found = true;
      break;
    }
@@ -1649,21 +1669,27 @@ parse_sanitizer_options (const char *p,
  {
    const char *hint
      = get_closest_sanitizer_option (string_fragment (p, len),
-         code, value);
+         opts, code, value);
+
+   const char *suffix;
+   if (code == OPT_fsanitize_recover_)
+     suffix = "-recover";
+   else if (code == OPT_fsanitize_coverage_)
+     suffix = "-coverage";
+   else
+     suffix = "";
 
    if (hint)
      error_at (loc,
         "unrecognized argument to -f%ssanitize%s= option: %q.*s;"
         " did you mean %qs?",
         value ? "" : "no-",
-        code == OPT_fsanitize_ ? "" : "-recover",
-        (int) len, p, hint);
+        suffix, (int) len, p, hint);
    else
      error_at (loc,
         "unrecognized argument to -f%ssanitize%s= option: %q.*s",
         value ? "" : "no-",
-        code == OPT_fsanitize_ ? "" : "-recover",
-        (int) len, p);
+        suffix, (int) len, p);
  }
 
       if (comma == NULL)
@@ -1956,6 +1982,12 @@ common_handle_option (struct gcc_options
    &= ~(SANITIZE_UNDEFINED | SANITIZE_UNDEFINED_NONDEFAULT);
       break;
 
+    case OPT_fsanitize_coverage_:
+      opts->x_flag_sanitize_coverage
+ = parse_sanitizer_options (arg, loc, code,
+       opts->x_flag_sanitize_coverage, value, true);
+      break;
+
     case OPT_O:
     case OPT_Os:
     case OPT_Ofast:
--- gcc/sancov.c.jj 2017-09-01 09:26:48.603612240 +0200
+++ gcc/sancov.c 2017-09-05 17:51:02.209865830 +0200
@@ -1,6 +1,7 @@
 /* Code coverage instrumentation for fuzzing.
    Copyright (C) 2015-2017 Free Software Foundation, Inc.
-   Contributed by Dmitry Vyukov <dvyukov@google.com>
+   Contributed by Dmitry Vyukov <dvyukov@google.com> and
+   Wish Wu <wishwu007@gmail.com>
 
 This file is part of GCC.
 
@@ -29,32 +30,271 @@ along with GCC; see the file COPYING3.
 #include "flags.h"
 #include "stmt.h"
 #include "gimple-iterator.h"
+#include "gimple-builder.h"
 #include "tree-cfg.h"
 #include "tree-pass.h"
 #include "tree-iterator.h"
+#include "fold-const.h"
 #include "stringpool.h"
 #include "attribs.h"
+#include "output.h"
+#include "cgraph.h"
 #include "asan.h"
 
 namespace {
 
+/* Instrument one comparison operation, which compares lhs and rhs.
+   Call the instrumentation function with the comparison operand.
+   For integral comparisons if exactly one of the comparison operands is
+   constant, call __sanitizer_cov_trace_const_cmp* instead of
+   __sanitizer_cov_trace_cmp*.  */
+
+static void
+instrument_comparison (gimple_stmt_iterator *gsi, tree lhs, tree rhs)
+{
+  tree type = TREE_TYPE (lhs);
+  enum built_in_function fncode = END_BUILTINS;
+  tree to_type = NULL_TREE;
+  bool c = false;
+
+  if (INTEGRAL_TYPE_P (type))
+    {
+      c = (is_gimple_min_invariant (lhs)
+    ^ is_gimple_min_invariant (rhs));
+      switch (int_size_in_bytes (type))
+ {
+ case 1:
+         fncode = c ? BUILT_IN_SANITIZER_COV_TRACE_CONST_CMP1
+       : BUILT_IN_SANITIZER_COV_TRACE_CMP1;
+   to_type = unsigned_char_type_node;
+   break;
+ case 2:
+         fncode = c ? BUILT_IN_SANITIZER_COV_TRACE_CONST_CMP2
+       : BUILT_IN_SANITIZER_COV_TRACE_CMP2;
+   to_type = uint16_type_node;
+   break;
+ case 4:
+         fncode = c ? BUILT_IN_SANITIZER_COV_TRACE_CONST_CMP4
+       : BUILT_IN_SANITIZER_COV_TRACE_CMP4;
+   to_type = uint32_type_node;
+   break;
+ default:
+         fncode = c ? BUILT_IN_SANITIZER_COV_TRACE_CONST_CMP8
+       : BUILT_IN_SANITIZER_COV_TRACE_CMP8;
+   to_type = uint64_type_node;
+   break;
+ }
+    }
+  else if (SCALAR_FLOAT_TYPE_P (type))
+    {
+      if (TYPE_MODE (type) == TYPE_MODE (float_type_node))
+ {
+         fncode = BUILT_IN_SANITIZER_COV_TRACE_CMPF;
+   to_type = float_type_node;
+ }
+      else if (TYPE_MODE (type) == TYPE_MODE (double_type_node))
+ {
+         fncode = BUILT_IN_SANITIZER_COV_TRACE_CMPD;
+   to_type = double_type_node;
+ }
+    }
+
+  if (to_type != NULL_TREE)
+    {
+      gimple_seq seq = NULL;
+
+      if (!useless_type_conversion_p (to_type, type))
+ {
+   if (TREE_CODE (lhs) == INTEGER_CST)
+     lhs = fold_convert (to_type, lhs);
+   else
+     {
+       gimple_seq_add_stmt (&seq, build_type_cast (to_type, lhs));
+       lhs = gimple_assign_lhs (gimple_seq_last_stmt (seq));
+     }
+
+   if (TREE_CODE (rhs) == INTEGER_CST)
+     rhs = fold_convert (to_type, rhs);
+   else
+     {
+       gimple_seq_add_stmt (&seq, build_type_cast (to_type, rhs));
+       rhs = gimple_assign_lhs (gimple_seq_last_stmt (seq));
+     }
+ }
+
+      if (c && !is_gimple_min_invariant (lhs))
+ std::swap (lhs, rhs);
+
+      tree fndecl = builtin_decl_implicit (fncode);
+      gimple *gcall = gimple_build_call (fndecl, 2, lhs, rhs);
+      gimple_seq_add_stmt (&seq, gcall);
+
+      gimple_seq_set_location (seq, gimple_location (gsi_stmt (*gsi)));
+      gsi_insert_seq_before (gsi, seq, GSI_SAME_STMT);
+    }
+}
+
+/* Instrument switch statement.  Call __sanitizer_cov_trace_switch with
+   the value of the index and array that contains number of case values,
+   the bitsize of the index and the case values converted to uint64_t.  */
+
+static void
+instrument_switch (gimple_stmt_iterator *gsi, gimple *stmt, function *fun)
+{
+  gswitch *switch_stmt = as_a<gswitch *> (stmt);
+  tree index = gimple_switch_index (switch_stmt);
+  HOST_WIDE_INT size_in_bytes = int_size_in_bytes (TREE_TYPE (index));
+  if (size_in_bytes == -1 || size_in_bytes > 8)
+    return;
+
+  location_t loc = gimple_location (stmt);
+  unsigned i, n = gimple_switch_num_labels (switch_stmt), num = 0;
+  for (i = 1; i < n; ++i)
+    {
+      tree label = gimple_switch_label (switch_stmt, i);
+
+      tree low_case = CASE_LOW (label);
+      if (low_case != NULL_TREE)
+ num++;
+
+      tree high_case = CASE_HIGH (label);
+      if (high_case != NULL_TREE)
+ num++;
+    }
+
+  tree case_array_type
+   = build_array_type (build_type_variant (uint64_type_node, 1, 0),
+         build_index_type (size_int (num + 2 - 1)));
+
+  char name[64];
+  static size_t case_array_count = 0;
+  ASM_GENERATE_INTERNAL_LABEL (name, "LCASEARRAY", case_array_count++);
+  tree case_array_var = build_decl (loc, VAR_DECL, get_identifier (name),
+        case_array_type);
+  TREE_STATIC (case_array_var) = 1;
+  TREE_PUBLIC (case_array_var) = 0;
+  TREE_CONSTANT (case_array_var) = 1;
+  TREE_READONLY (case_array_var) = 1;
+  DECL_EXTERNAL (case_array_var) = 0;
+  DECL_ARTIFICIAL (case_array_var) = 1;
+  DECL_IGNORED_P (case_array_var) = 1;
+
+  vec <constructor_elt, va_gc> *v = NULL;
+  vec_alloc (v, num + 2);
+  CONSTRUCTOR_APPEND_ELT (v, NULL_TREE,
+     build_int_cst (uint64_type_node, num));
+  CONSTRUCTOR_APPEND_ELT (v, NULL_TREE,
+     build_int_cst (uint64_type_node,
+      size_in_bytes * BITS_PER_UNIT));
+  for (i = 1; i < n; ++i)
+    {
+      tree label = gimple_switch_label (switch_stmt, i);
+
+      tree low_case = CASE_LOW (label);
+      if (low_case != NULL_TREE)
+ CONSTRUCTOR_APPEND_ELT (v, NULL_TREE,
+    fold_convert (uint64_type_node, low_case));
+
+      tree high_case = CASE_HIGH (label);
+      if (high_case != NULL_TREE)
+ CONSTRUCTOR_APPEND_ELT (v, NULL_TREE,
+    fold_convert (uint64_type_node, high_case));
+    }
+  tree ctor = build_constructor (case_array_type, v);
+  TREE_STATIC (ctor) = 1;
+  TREE_PUBLIC (ctor) = 0;
+  TREE_CONSTANT (ctor) = 1;
+  TREE_READONLY (ctor) = 1;
+  DECL_INITIAL (case_array_var) = ctor;
+  varpool_node::finalize_decl (case_array_var);
+  add_local_decl (fun, case_array_var);
+
+  gimple_seq seq = NULL;
+
+  if (!useless_type_conversion_p (uint64_type_node, TREE_TYPE (index)))
+    {
+      if (TREE_CODE (index) == INTEGER_CST)
+ index = fold_convert (uint64_type_node, index);
+      else
+ {
+   gimple_seq_add_stmt (&seq, build_type_cast (uint64_type_node, index));
+   index = gimple_assign_lhs (gimple_seq_last_stmt (seq));
+ }
+    }
+
+  tree fndecl = builtin_decl_implicit (BUILT_IN_SANITIZER_COV_TRACE_SWITCH);
+  gimple *gcall = gimple_build_call (fndecl, 2, index,
+         build_fold_addr_expr (case_array_var));
+  gimple_seq_add_stmt (&seq, gcall);
+
+  gimple_seq_set_location (seq, loc);
+  gsi_insert_seq_before (gsi, seq, GSI_SAME_STMT);
+}
+
 unsigned
 sancov_pass (function *fun)
 {
   initialize_sanitizer_builtins ();
 
   /* Insert callback into beginning of every BB. */
-  tree fndecl = builtin_decl_implicit (BUILT_IN_SANITIZER_COV_TRACE_PC);
-  basic_block bb;
-  FOR_EACH_BB_FN (bb, fun)
-    {
-      gimple_stmt_iterator gsi = gsi_start_nondebug_after_labels_bb (bb);
-      if (gsi_end_p (gsi))
- continue;
-      gimple *stmt = gsi_stmt (gsi);
-      gimple *gcall = gimple_build_call (fndecl, 0);
-      gimple_set_location (gcall, gimple_location (stmt));
-      gsi_insert_before (&gsi, gcall, GSI_SAME_STMT);
+  if (flag_sanitize_coverage & SANITIZE_COV_TRACE_PC)
+    {
+      basic_block bb;
+      tree fndecl = builtin_decl_implicit (BUILT_IN_SANITIZER_COV_TRACE_PC);
+      FOR_EACH_BB_FN (bb, fun)
+ {
+   gimple_stmt_iterator gsi = gsi_start_nondebug_after_labels_bb (bb);
+   if (gsi_end_p (gsi))
+     continue;
+   gimple *stmt = gsi_stmt (gsi);
+   gimple *gcall = gimple_build_call (fndecl, 0);
+   gimple_set_location (gcall, gimple_location (stmt));
+   gsi_insert_before (&gsi, gcall, GSI_SAME_STMT);
+ }
+    }
+
+  /* Insert callback into every comparison related operation.  */
+  if (flag_sanitize_coverage & SANITIZE_COV_TRACE_CMP)
+    {
+      basic_block bb;
+      FOR_EACH_BB_FN (bb, fun)
+ {
+   gimple_stmt_iterator gsi;
+   for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+     {
+       gimple *stmt = gsi_stmt (gsi);
+       enum tree_code rhs_code;
+       switch (gimple_code (stmt))
+  {
+  case GIMPLE_ASSIGN:
+    rhs_code = gimple_assign_rhs_code (stmt);
+    if (TREE_CODE_CLASS (rhs_code) == tcc_comparison)
+      instrument_comparison (&gsi,
+        gimple_assign_rhs1 (stmt),
+        gimple_assign_rhs2 (stmt));
+    else if (rhs_code == COND_EXPR
+      && COMPARISON_CLASS_P (gimple_assign_rhs1 (stmt)))
+      {
+        tree cond = gimple_assign_rhs1 (stmt);
+        instrument_comparison (&gsi, TREE_OPERAND (cond, 0),
+          TREE_OPERAND (cond, 1));
+      }
+    break;
+  case GIMPLE_COND:
+    instrument_comparison (&gsi,
+      gimple_cond_lhs (stmt),
+      gimple_cond_rhs (stmt));
+    break;
+
+  case GIMPLE_SWITCH:
+    instrument_switch (&gsi, stmt, fun);
+    break;
+
+  default:
+    break;
+  }
+     }
+ }
     }
   return 0;
 }
--- gcc/sanitizer.def.jj 2017-07-28 12:35:27.565412232 +0200
+++ gcc/sanitizer.def 2017-09-05 17:01:51.281308488 +0200
@@ -537,6 +537,39 @@ DEF_SANITIZER_BUILTIN(BUILT_IN_UBSAN_HAN
 DEF_SANITIZER_BUILTIN(BUILT_IN_SANITIZER_COV_TRACE_PC,
         "__sanitizer_cov_trace_pc",
         BT_FN_VOID, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_SANITIZER_COV_TRACE_CMP1,
+        "__sanitizer_cov_trace_cmp1",
+        BT_FN_VOID_UINT8_UINT8, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_SANITIZER_COV_TRACE_CMP2,
+        "__sanitizer_cov_trace_cmp2",
+        BT_FN_VOID_UINT16_UINT16, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_SANITIZER_COV_TRACE_CMP4,
+        "__sanitizer_cov_trace_cmp4",
+        BT_FN_VOID_UINT32_UINT32, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_SANITIZER_COV_TRACE_CMP8,
+        "__sanitizer_cov_trace_cmp8",
+        BT_FN_VOID_UINT64_UINT64, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_SANITIZER_COV_TRACE_CONST_CMP1,
+        "__sanitizer_cov_trace_const_cmp1",
+        BT_FN_VOID_UINT8_UINT8, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_SANITIZER_COV_TRACE_CONST_CMP2,
+        "__sanitizer_cov_trace_const_cmp2",
+        BT_FN_VOID_UINT16_UINT16, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_SANITIZER_COV_TRACE_CONST_CMP4,
+        "__sanitizer_cov_trace_const_cmp4",
+        BT_FN_VOID_UINT32_UINT32, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_SANITIZER_COV_TRACE_CONST_CMP8,
+        "__sanitizer_cov_trace_const_cmp8",
+        BT_FN_VOID_UINT64_UINT64, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_SANITIZER_COV_TRACE_CMPF,
+        "__sanitizer_cov_trace_cmpf",
+        BT_FN_VOID_FLOAT_FLOAT, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_SANITIZER_COV_TRACE_CMPD,
+        "__sanitizer_cov_trace_cmpd",
+        BT_FN_VOID_DOUBLE_DOUBLE, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_SANITIZER_COV_TRACE_SWITCH,
+        "__sanitizer_cov_trace_switch",
+        BT_FN_VOID_UINT64_PTR, ATTR_NOTHROW_LEAF_LIST)
 
 /* This has to come after all the sanitizer builtins.  */
 DEF_BUILTIN_STUB(END_SANITIZER_BUILTINS, (const char *)0)
--- gcc/tree-ssa-ifcombine.c.jj 2017-06-30 09:49:28.004662123 +0200
+++ gcc/tree-ssa-ifcombine.c 2017-09-05 15:39:32.460612633 +0200
@@ -560,7 +560,7 @@ ifcombine_ifandif (basic_block inner_con
  {
    tree t1, t2;
    gimple_stmt_iterator gsi;
-   if (!LOGICAL_OP_NON_SHORT_CIRCUIT)
+   if (!LOGICAL_OP_NON_SHORT_CIRCUIT || flag_sanitize_coverage)
      return false;
    /* Only do this optimization if the inner bb contains only the conditional. */
    if (!gsi_one_before_end_p (gsi_start_nondebug_after_labels_bb (inner_cond_bb)))
--- gcc/doc/invoke.texi.jj 2017-09-04 09:55:25.000000000 +0200
+++ gcc/doc/invoke.texi 2017-09-05 18:22:02.863499354 +0200
@@ -11161,6 +11161,20 @@ is usable even in freestanding environme
 Enable coverage-guided fuzzing code instrumentation.
 Inserts a call to @code{__sanitizer_cov_trace_pc} into every basic block.
 
+@item -fsanitize-coverage=trace-cmp
+@opindex fsanitize-coverage=trace-cmp
+Enable dataflow guided fuzzing code instrumentation.
+Inserts a call to @code{__sanitizer_cov_trace_cmp1},
+@code{__sanitizer_cov_trace_cmp2}, @code{__sanitizer_cov_trace_cmp4} or
+@code{__sanitizer_cov_trace_cmp8} for integral comparison with both operands
+variable or @code{__sanitizer_cov_trace_const_cmp1},
+@code{__sanitizer_cov_trace_const_cmp2},
+@code{__sanitizer_cov_trace_const_cmp4} or
+@code{__sanitizer_cov_trace_const_cmp8} for integral comparison with one
+operand constant, @code{__sanitizer_cov_trace_cmpf} or
+@code{__sanitizer_cov_trace_cmpd} for float or double comparisons and
+@code{__sanitizer_cov_trace_switch} for switch statements.
+
 @item -fbounds-check
 @opindex fbounds-check
 For front ends that support it, generate additional code to check that
--- gcc/testsuite/gcc.dg/sancov/cmp0.c.jj 2017-09-05 17:54:00.906717081 +0200
+++ gcc/testsuite/gcc.dg/sancov/cmp0.c 2017-09-05 18:04:15.319329045 +0200
@@ -0,0 +1,92 @@
+/* Basic test on number of inserted callbacks.  */
+/* { dg-do compile } */
+/* { dg-options "-fsanitize-coverage=trace-cmp -fdump-tree-optimized" } */
+
+void
+foo (char *a, short *b, int *c, long long *d, float *e, double *f)
+{
+  if (*a)
+    *a += 1;
+  if (*b)
+    *b = *a;
+  if (*c)
+    *c += 1;
+  if (*d)
+    *d = *c;
+  if (*e == *c)
+    *e = *c;
+  if (*f == *e)
+    *f = *e;
+  switch (*a)
+    {
+    case 2:
+      *b += 2;
+      break;
+    case 3:
+      *b += 3;
+      break;
+    case 4:
+      *b += 4;
+      break;
+    case 5:
+      *b += 5;
+      break;
+    case 6:
+      *b += 6;
+      break;
+    case 7 ... 24:
+      *b += 7;
+      break;
+    default:
+      break;
+    }
+  switch (*d)
+    {
+    case 3:
+      *d += 3;
+    case -4:
+      *d -= 4;
+    case -5:
+      *d -= 5;
+    case -6:
+      *d -= 6;
+    case -7:
+      *d -= 7;
+    case -8:
+      *d -= 8;
+    case -9:
+      *d -= 9;
+    case -10:
+      *d -= 10;
+    }
+}
+
+void
+bar (int *c)
+{
+  if (*c == 27)
+    *c += 2;
+  if (*c == 37)
+    *c += 2;
+}
+
+int
+baz (int *c, long long d, long long e)
+{
+  *c = (*c == 48) ? 12 : 24;
+  return d == e;
+}
+
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_const_cmp1 \\(0, " 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_const_cmp2 \\(0, " 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_const_cmp4 \\(0, " 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_const_cmp8 \\(0, " 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_const_cmp4 \\(27, " 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_const_cmp4 \\(37, " 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_const_cmp4 \\(48, " 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_cmp8 \\(" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_cmpf \\(" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_cmpd \\(" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_const_cmp" 7 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_cmp" 3 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_switch \\(" 2 "optimized" } } */


 Jakub