[PATCH] Try harder to delegitimize GOTOFF addresses on i?86 (PR target/43139)

[Jakub Jelinek <jakub at redhat dot com>]

Hi!

The testcase below ICEs on redhat/gcc-4_4-branch, because a GOTOFF
reloc doesn't use %ebx as base register, but instead another register (%ecx
in this case), which has been set earlier using leal (%ebx, %ecx, 8), %ecx
(this %ecx is used multiple times in a loop in several insns, so it looks
like a good idea).  Unfortunately, ix86_delegitimize_address is not able
to delegitimize such addresses, as it requires that the base register is
%ebx (or %ebx + some other reg * {1,2,4,8}) and when var-tracking finds out
some register is live in such a location, we ICE as @GOTOFF UNSPEC is not
meant to be output into .debug_info section data.

While I don't have a testcase that would ICE the same way on the trunk, I
believe the issue is just latent there and trunk bootstrap many times calls
ix86_delegitimize_address with @GOTOFF UNSPECs not based on pic pointer,
just var-tracking didn't find during bootstrap a case where something would
be live only in that location and not elsewhere.

The patch below fixes it by delegitimizing even @GOTOFF UNSPECs that aren't
based on pic pointer - in that case it delegitimizes it to (addend - %ebx) + (symbol_ref)

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

2010-02-23  Jakub Jelinek  <jakub@redhat.com>

	PR target/43139
	* config/i386/i386.c (ix86_delegitimize_address): Delegitimize all
	GOTOFF relocs, even when the base reg isn't pic pointer.

	* gcc.dg/pr43139.c: New test.

--- gcc/config/i386/i386.c.jj	2010-02-11 13:09:21.000000000 +0100
+++ gcc/config/i386/i386.c	2010-02-22 14:53:34.000000000 +0100
@@ -10827,6 +10827,7 @@ static rtx
 ix86_delegitimize_address (rtx x)
 {
   rtx orig_x = delegitimize_mem_from_attrs (x);
+  rtx addend = NULL_RTX;
   /* reg_addend is NULL or a multiple of some register.  */
   rtx reg_addend = NULL_RTX;
   /* const_addend is NULL or a const_int.  */
@@ -10865,14 +10866,13 @@ ix86_delegitimize_address (rtx x)
       else if (ix86_pic_register_p (XEXP (reg_addend, 1)))
 	reg_addend = XEXP (reg_addend, 0);
       else
-	return orig_x;
-      if (!REG_P (reg_addend)
-	  && GET_CODE (reg_addend) != MULT
-	  && GET_CODE (reg_addend) != ASHIFT)
-	return orig_x;
+	{
+	  reg_addend = NULL_RTX;
+	  addend = XEXP (x, 0);
+	}
     }
   else
-    return orig_x;
+    addend = XEXP (x, 0);
 
   x = XEXP (XEXP (x, 1), 0);
   if (GET_CODE (x) == PLUS
@@ -10883,7 +10883,7 @@ ix86_delegitimize_address (rtx x)
     }
 
   if (GET_CODE (x) == UNSPEC
-      && ((XINT (x, 1) == UNSPEC_GOT && MEM_P (orig_x))
+      && ((XINT (x, 1) == UNSPEC_GOT && MEM_P (orig_x) && !addend)
 	  || (XINT (x, 1) == UNSPEC_GOTOFF && !MEM_P (orig_x))))
     result = XVECEXP (x, 0, 0);
 
@@ -10898,6 +10898,15 @@ ix86_delegitimize_address (rtx x)
     result = gen_rtx_CONST (Pmode, gen_rtx_PLUS (Pmode, result, const_addend));
   if (reg_addend)
     result = gen_rtx_PLUS (Pmode, reg_addend, result);
+  if (addend)
+    {
+      if (pic_offset_table_rtx)
+        result = gen_rtx_PLUS (Pmode, gen_rtx_MINUS (Pmode, copy_rtx (addend),
+						     pic_offset_table_rtx),
+			       result);
+      else
+	return orig_x;
+    }
   return result;
 }
 
--- gcc/testsuite/gcc.dg/pr43139.c.jj	2010-02-22 16:07:23.000000000 +0100
+++ gcc/testsuite/gcc.dg/pr43139.c	2010-02-22 16:04:30.000000000 +0100
@@ -0,0 +1,59 @@
+/* PR target/43139 */
+/* { dg-do compile { target fpic } } */
+/* { dg-options "-g -O2 -fpic" } */
+
+typedef double T1[10];
+typedef double T2[10][10];
+typedef int T3[10];
+
+void __attribute__((noinline))
+fn1 (void)
+{
+  asm volatile ("" : : : "memory");
+}
+
+void __attribute__((noinline))
+fn2 (int x, ...)
+{
+  asm volatile ("" : : "r" (x) : "memory");
+}
+
+static void
+bar (double v, double w, double x, double y, double z)
+{
+  double a;
+  if (v / w < 200.0)
+    {
+      a = x + (y - x) * __builtin_exp (-v / w);
+      fn2 (0);
+      fn2 (1, a * 20.2 / z, z);
+      fn1 ();
+    }
+}
+
+static void
+baz (T2 u, T2 v, T2 t, T2 x, T1 y, T3 z, double q, int j, int k)
+{
+  int i = z[k];
+  if (u[i][j] > 0.0)
+    bar (q, x[i][j], v[i][j], t[i][j], y[i]);
+}
+
+static T2 a, b, c, d;
+static T1 e;
+static T3 f;
+
+void __attribute__((noinline))
+test (int j, int k, double q)
+{
+  baz (a, b, c, d, e, f, q, j, k);
+}
+
+int
+main (void)
+{
+  d[0][6] = 1.0;
+  a[0][6] = 2.0;
+  test (6, 7, 400.0);
+  return 0;
+}

	Jakub