[PATCH] combine: Fix PR80233

[Segher Boessenkool]

If combine has added an unconditional trap there will be a new basic
block as well.  It will then end up considering the NOTE_INSN_BASIC_BLOCK
as the last_combined_insn, but then it tries to take the DF_INSN_LUID
of that and that dereferences a NULL pointer (since such a note is not
an INSN_P).

This fixes it by not taking non-insns as last_combined_insn.

Bootstrapped and tested on powerpc64-linux {-m32,-m64}.


Segher


2017-03-29  Segher Boessenkool  <segher@kernel.crashing.org>

	PR rtl-optimization/80233
	* combine.c (combine_instructions): Only take NONDEBUG_INSN_P insns
	as last_combined_insn.  Do not test for BARRIER_P separately.

gcc/testsuite/
	PR rtl-optimization/80233
	* gcc.c-torture/compile/pr80233.c: New testcase.

---
 gcc/combine.c                                 |  4 ++--
 gcc/testsuite/gcc.c-torture/compile/pr80233.c | 22 ++++++++++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr80233.c

diff --git a/gcc/combine.c b/gcc/combine.c
index 87e9670..88ac475 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -1250,10 +1250,10 @@ combine_instructions (rtx_insn *f, unsigned int nregs)
 	    continue;
 
 	  while (last_combined_insn
-		 && last_combined_insn->deleted ())
+		 && (!NONDEBUG_INSN_P (last_combined_insn)
+		     || last_combined_insn->deleted ()))
 	    last_combined_insn = PREV_INSN (last_combined_insn);
 	  if (last_combined_insn == NULL_RTX
-	      || BARRIER_P (last_combined_insn)
 	      || BLOCK_FOR_INSN (last_combined_insn) != this_basic_block
 	      || DF_INSN_LUID (last_combined_insn) <= DF_INSN_LUID (insn))
 	    last_combined_insn = insn;
diff --git a/gcc/testsuite/gcc.c-torture/compile/pr80233.c b/gcc/testsuite/gcc.c-torture/compile/pr80233.c
new file mode 100644
index 0000000..eb9b4a4
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr80233.c
@@ -0,0 +1,22 @@
+/* PR rtl-optimization/80233 */
+
+int xg;
+
+void
+t4 (int o9)
+{
+  int it;
+
+  if (o9 == 0)
+    {
+      int fx;
+
+      xg *= it;
+      if (xg == 0)
+        it /= 0;
+
+      fx = (it != 0) ? (xg < 0) : (xg / o9);
+      if (fx != 0)
+        xg = 0;
+    }
+}
-- 
1.9.3