[PATCH] Fix dwarf2out ICE with UNSPEC_GOTOFF (PR debug/82837)

[Jakub Jelinek <jakub at redhat dot com>]

Hi!

My recent changes to const_ok_for_output_1 to allow UNSPEC if target hook
says it is ok for debug regressed the following testcase, where creative
simplify-rtx.c changes result in (const (neg (unspec ... UNSPEC_GOTOFF)))
being emitted and the backend not being able to assemble that (assembler
has no such relocations).
We already have a hack to avoid ICEing on NOT in similar cases, this patch
adds NEG to that.  And, in mem_loc_descriptor tries harder to handle these
cases right - while if we have say (const (not (symbol_ref))) the current
code would handle it right already, if there is the unspec, we really need
it to be wrapped inside of CONST, otherwise it is dropped on the floor.

The patch in that case emits (const (neg (unspec ... UNSPEC_GOTOFF)))
as (neg (const (unspec ... UNSPEC_GOTOFF))).

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2017-11-06  Jakub Jelinek  <jakub@redhat.com>

	PR debug/82837
	* dwarf2out.c (const_ok_for_output_1): Reject NEG in addition to NOT.
	(mem_loc_descriptor): Handle (const (neg (...))) as (neg (const (...)))
	and similarly for not instead of neg.

	* gcc.dg/debug/dwarf2/pr82837.c: New test.

--- gcc/dwarf2out.c.jj	2017-11-01 22:49:18.000000000 +0100
+++ gcc/dwarf2out.c	2017-11-06 18:52:28.047287983 +0100
@@ -13782,10 +13782,14 @@ const_ok_for_output_1 (rtx rtl)
      We should really identify / validate expressions
      enclosed in CONST that can be handled by assemblers on various
      targets and only handle legitimate cases here.  */
-  if (GET_CODE (rtl) != SYMBOL_REF)
+  switch (GET_CODE (rtl))
     {
-      if (GET_CODE (rtl) == NOT)
-	return false;
+    case SYMBOL_REF:
+      break;
+    case NOT:
+    case NEG:
+      return false;
+    default:
       return true;
     }
 
@@ -14958,8 +14962,32 @@ mem_loc_descriptor (rtx rtl, machine_mod
       if (!const_ok_for_output (rtl))
 	{
 	  if (GET_CODE (rtl) == CONST)
-	    mem_loc_result = mem_loc_descriptor (XEXP (rtl, 0), int_mode,
-						 mem_mode, initialized);
+	    switch (GET_CODE (XEXP (rtl, 0)))
+	      {
+	      case NOT:
+		op = DW_OP_not;
+		goto try_const_unop;
+	      case NEG:
+		op = DW_OP_neg;
+		goto try_const_unop;
+	      try_const_unop:
+		rtx arg;
+		arg = XEXP (XEXP (rtl, 0), 0);
+		if (!CONSTANT_P (arg))
+		  arg = gen_rtx_CONST (int_mode, arg);
+		op0 = mem_loc_descriptor (arg, int_mode, mem_mode,
+					  initialized);
+		if (op0)
+		  {
+		    mem_loc_result = op0;
+		    add_loc_descr (&mem_loc_result, new_loc_descr (op, 0, 0));
+		  }
+		break;
+	      default:
+		mem_loc_result = mem_loc_descriptor (XEXP (rtl, 0), int_mode,
+						     mem_mode, initialized);
+		break;
+	      }
 	  break;
 	}
 
--- gcc/testsuite/gcc.dg/debug/dwarf2/pr82837.c.jj	2017-11-06 18:38:19.365703290 +0100
+++ gcc/testsuite/gcc.dg/debug/dwarf2/pr82837.c	2017-11-06 18:52:07.759536945 +0100
@@ -0,0 +1,29 @@
+/* PR debug/82837 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -g" } */
+/* { dg-additional-options "-march=athlon" { target ia32 } } */
+/* { dg-additional-options "-fPIE" { target pie } } */
+
+static char b[100];
+static int *c;
+char *e;
+void a(char *f, char *i) {
+  int d = __builtin_object_size(f, 1);
+  __builtin___strcpy_chk(f, i, d);
+}
+void g(void) {
+  int h;
+  switch (*c) {
+  case 8:
+    e = "swapgs";
+    break;
+  case 9:
+    e = "rdtscp";
+    break;
+  default:
+    return;
+  }
+  h = __builtin_strlen(b);
+  a(b + h - 6, e);
+  c++;
+}

	Jakub