expmed.c (extract_force_align_mem_bit_field): Correct handling at the end of a page.

        * expmed.c (extract_force_align_mem_bit_field): Correct handling at
        the end of a page.

From-SVN: r90288

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index da58911..3e43541 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2004-11-08  Richard Henderson  <rth@redhat.com>
+
+       * expmed.c (extract_force_align_mem_bit_field): Correct handling at
+       the end of a page.
+
 2004-11-08  Kazu Hirata  <kazu@cs.umass.edu>
 
        * sched-deps.c (add_insn_mem_dependence): Make it static.

diff --git a/gcc/expmed.c b/gcc/expmed.c
index a108efa..191df72 100644 (file)
--- a/gcc/expmed.c
+++ b/gcc/expmed.c
@@ -1891,11 +1891,16 @@ extract_force_align_mem_bit_field (rtx op0, unsigned HOST_WIDE_INT bitsize,
   if (STRICT_ALIGNMENT)
     {
       base = plus_constant (XEXP (op0, 0), bitpos / BITS_PER_UNIT);
-      base = force_operand (base, NULL);
       bitpos %= BITS_PER_UNIT;
 
-      /* Force alignment of the address; load two sequential values.  */
-      a1 = expand_simple_binop (Pmode, AND, base,
+      /* We load two values to be concatenate.  There's an edge condition
+        that bears notice -- an aligned value at the end of a page can
+        only load one value lest we segfault.  So the two values we load
+        are at "base & -size" and "(base + size - 1) & -size".  If base
+        is unaligned, the addresses will be aligned and sequential; if
+        base is aligned, the addresses will both be equal to base.  */
+
+      a1 = expand_simple_binop (Pmode, AND, force_operand (base, NULL),
                                GEN_INT (-(HOST_WIDE_INT)m_size),
                                NULL, true, OPTAB_LIB_WIDEN);
       mark_reg_pointer (a1, m_bitsize);
@@ -1903,7 +1908,10 @@ extract_force_align_mem_bit_field (rtx op0, unsigned HOST_WIDE_INT bitsize,
       set_mem_align (v1, m_bitsize);
       v1 = force_reg (mode, validize_mem (v1));
 
-      a2 = plus_constant (a1, GET_MODE_SIZE (mode));
+      a2 = plus_constant (base, GET_MODE_SIZE (mode) - 1);
+      a2 = expand_simple_binop (Pmode, AND, force_operand (a2, NULL),
+                               GEN_INT (-(HOST_WIDE_INT)m_size),
+                               NULL, true, OPTAB_LIB_WIDEN);
       v2 = gen_rtx_MEM (mode, a2);
       set_mem_align (v2, m_bitsize);
       v2 = force_reg (mode, validize_mem (v2));