[PR103024,PR103530] support throwing compares and non-boolean types in harden-compares

This patch adjusts the harden-compares pass to cope with compares that
must end basic blocks, and to accept non-boolean integral types whose
conversion to boolean may have been discarded.

(Andrew, thanks for the tip on how the discarding comes about, it's
saved me some head-scratching and investigation ;-)

Regstrapped on x86_64-linux-gnu.  Ok to install?


for  gcc/ChangeLog

	PR tree-optimization/103024
	PR middle-end/103530
	* gimple-harden-conditionals.cc (non_eh_succ_edge): New.
	(pass_harden_compares::execute): Accept 1-bit integral types,
	and cope with throwing compares.

for  gcc/testsuite/ChangeLog

	PR tree-optimization/103024
	PR middle-end/103530
	* g++.dg/pr103024.C: New.
	* g++.dg/pr103530.C: New.
---
 gcc/gimple-harden-conditionals.cc |   74 +++++++++++++++++++++++++++++++++++--
 gcc/testsuite/g++.dg/pr103024.C   |   12 ++++++
 gcc/testsuite/g++.dg/pr103530.C   |   27 ++++++++++++++
 3 files changed, 109 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/pr103024.C
 create mode 100644 gcc/testsuite/g++.dg/pr103530.C

On December 8, 2021 2:57:15 AM GMT+01:00, Alexandre Oliva via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
>
>This patch adjusts the harden-compares pass to cope with compares that
>must end basic blocks, and to accept non-boolean integral types whose
>conversion to boolean may have been discarded.
>
>(Andrew, thanks for the tip on how the discarding comes about, it's
>saved me some head-scratching and investigation ;-)
>
>Regstrapped on x86_64-linux-gnu.  Ok to install?

Ok. 

Richard. 

>
>for  gcc/ChangeLog
>
>	PR tree-optimization/103024
>	PR middle-end/103530
>	* gimple-harden-conditionals.cc (non_eh_succ_edge): New.
>	(pass_harden_compares::execute): Accept 1-bit integral types,
>	and cope with throwing compares.
>
>for  gcc/testsuite/ChangeLog
>
>	PR tree-optimization/103024
>	PR middle-end/103530
>	* g++.dg/pr103024.C: New.
>	* g++.dg/pr103530.C: New.
>---
> gcc/gimple-harden-conditionals.cc |   74 +++++++++++++++++++++++++++++++++++--
> gcc/testsuite/g++.dg/pr103024.C   |   12 ++++++
> gcc/testsuite/g++.dg/pr103530.C   |   27 ++++++++++++++
> 3 files changed, 109 insertions(+), 4 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/pr103024.C
> create mode 100644 gcc/testsuite/g++.dg/pr103530.C
>
>diff --git a/gcc/gimple-harden-conditionals.cc b/gcc/gimple-harden-conditionals.cc
>index 81867d6e4275f..5e709c66416b7 100644
>--- a/gcc/gimple-harden-conditionals.cc
>+++ b/gcc/gimple-harden-conditionals.cc
>@@ -35,6 +35,7 @@ along with GCC; see the file COPYING3.  If not see
> #include "basic-block.h"
> #include "cfghooks.h"
> #include "cfgloop.h"
>+#include "tree-eh.h"
> #include "diagnostic.h"
> #include "intl.h"
> 
>@@ -359,6 +360,24 @@ make_pass_harden_conditional_branches (gcc::context *ctxt)
>   return new pass_harden_conditional_branches (ctxt);
> }
> 
>+/* Return the fallthru edge of a block whose other edge is an EH
>+   edge.  */
>+static inline edge
>+non_eh_succ_edge (basic_block bb)
>+{
>+  gcc_checking_assert (EDGE_COUNT (bb->succs) == 2);
>+
>+  edge ret = find_fallthru_edge (bb->succs);
>+
>+  int eh_idx = EDGE_SUCC (bb, 0) == ret;
>+  edge eh = EDGE_SUCC (bb, eh_idx);
>+
>+  gcc_checking_assert (!(ret->flags & EDGE_EH)
>+		       && (eh->flags & EDGE_EH));
>+
>+  return ret;
>+}
>+
> /* Harden boolean-yielding compares in FUN.  */
> 
> unsigned int
>@@ -449,7 +468,11 @@ pass_harden_compares::execute (function *fun)
> 	if (VECTOR_TYPE_P (TREE_TYPE (op1)))
> 	  continue;
> 
>-	gcc_checking_assert (TREE_CODE (TREE_TYPE (lhs)) == BOOLEAN_TYPE);
>+	/* useless_type_conversion_p enables conversions from 1-bit
>+	   integer types to boolean to be discarded.  */
>+	gcc_checking_assert (TREE_CODE (TREE_TYPE (lhs)) == BOOLEAN_TYPE
>+			     || (INTEGRAL_TYPE_P (TREE_TYPE (lhs))
>+				 && TYPE_PRECISION (TREE_TYPE (lhs)) == 1));
> 
> 	tree rhs = copy_ssa_name (lhs);
> 
>@@ -460,6 +483,20 @@ pass_harden_compares::execute (function *fun)
> 	   won't be debug stmts only.  */
> 	gsi_next_nondebug (&gsi_split);
> 
>+	bool throwing_compare_p = stmt_ends_bb_p (asgn);
>+	if (throwing_compare_p)
>+	  {
>+	    basic_block nbb = split_edge (non_eh_succ_edge
>+					  (gimple_bb (asgn)));
>+	    gsi_split = gsi_start_bb (nbb);
>+
>+	    if (dump_file)
>+	      fprintf (dump_file,
>+		       "Splitting non-EH edge from block %i into %i"
>+		       " after a throwing compare\n",
>+		       gimple_bb (asgn)->index, nbb->index);
>+	  }
>+
> 	bool same_p = (op1 == op2);
> 	op1 = detach_value (loc, &gsi_split, op1);
> 	op2 = same_p ? op1 : detach_value (loc, &gsi_split, op2);
>@@ -473,17 +510,46 @@ pass_harden_compares::execute (function *fun)
> 	if (!gsi_end_p (gsi_split))
> 	  {
> 	    gsi_prev (&gsi_split);
>-	    split_block (bb, gsi_stmt (gsi_split));
>+	    basic_block obb = gsi_bb (gsi_split);
>+	    basic_block nbb = split_block (obb, gsi_stmt (gsi_split))->dest;
> 	    gsi_next (&gsi_split);
> 	    gcc_checking_assert (gsi_end_p (gsi_split));
> 
> 	    single_succ_edge (bb)->goto_locus = loc;
> 
> 	    if (dump_file)
>-	      fprintf (dump_file, "Splitting block %i\n", bb->index);
>+	      fprintf (dump_file,
>+		       "Splitting block %i into %i"
>+		       " before the conditional trap branch\n",
>+		       obb->index, nbb->index);
>+	  }
>+
>+	/* If the check assignment must end a basic block, we can't
>+	   insert the conditional branch in the same block, so split
>+	   the block again, and prepare to insert the conditional
>+	   branch in the new block.
>+
>+	   Also assign an EH region to the compare.  Even though it's
>+	   unlikely that the hardening compare will throw after the
>+	   original compare didn't, the compiler won't even know that
>+	   it's the same compare operands, so add the EH edge anyway.  */
>+	if (throwing_compare_p)
>+	  {
>+	    add_stmt_to_eh_lp (asgnck, lookup_stmt_eh_lp (asgn));
>+	    make_eh_edges (asgnck);
>+
>+	    basic_block nbb = split_edge (non_eh_succ_edge
>+					  (gimple_bb (asgnck)));
>+	    gsi_split = gsi_start_bb (nbb);
>+
>+	    if (dump_file)
>+	      fprintf (dump_file,
>+		       "Splitting non-EH edge from block %i into %i after"
>+		       " the newly-inserted reversed throwing compare\n",
>+		       gimple_bb (asgnck)->index, nbb->index);
> 	  }
> 
>-	gcc_checking_assert (single_succ_p (bb));
>+	gcc_checking_assert (single_succ_p (gsi_bb (gsi_split)));
> 
> 	insert_check_and_trap (loc, &gsi_split, EDGE_TRUE_VALUE,
> 			       EQ_EXPR, lhs, rhs);
>diff --git a/gcc/testsuite/g++.dg/pr103024.C b/gcc/testsuite/g++.dg/pr103024.C
>new file mode 100644
>index 0000000000000..15e68d4021328
>--- /dev/null
>+++ b/gcc/testsuite/g++.dg/pr103024.C
>@@ -0,0 +1,12 @@
>+/* { dg-do compile } */
>+/* { dg-options "-fnon-call-exceptions -fharden-compares -fsignaling-nans" } */
>+
>+struct G4ErrorMatrix {
>+  G4ErrorMatrix(int);
>+  ~G4ErrorMatrix();
>+};
>+double PropagateError_charge;
>+void PropagateError() {
>+  G4ErrorMatrix transf(0);
>+  int field(PropagateError_charge && field);
>+}
>diff --git a/gcc/testsuite/g++.dg/pr103530.C b/gcc/testsuite/g++.dg/pr103530.C
>new file mode 100644
>index 0000000000000..c1d2059542ba3
>--- /dev/null
>+++ b/gcc/testsuite/g++.dg/pr103530.C
>@@ -0,0 +1,27 @@
>+/* { dg-do compile } */
>+/* { dg-options "-O -fharden-compares -Wno-c++11-extensions" } */
>+
>+enum E:bool
>+{ E0, E1 };
>+
>+int x;
>+
>+E
>+baz (E rtt)
>+{
>+  return rtt == E0 ? E1 : E0;
>+}
>+
>+bool bar ();
>+
>+void
>+foo (E)
>+{
>+  E a = x ? E1 : E0;
>+  if (bar ())
>+    if (bar ())
>+      {
>+	E b = baz (a);
>+	foo (b);
>+      }
>+}
>
>