re PR target/27971 (eliminate shift in array[(x>>2)&3])

gcc/ChangeLog
       PR rtl-optimization/27971
       * combine.c (find_split_point): introduced a new split for certain
       types of mem rtx.

gcc/testsuite/ChangeLog

       PR rtl-optimization/27971
       * gcc.target/i386/pr27971.c: New testcase.

From-SVN: r131460

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5a47a8c611c1fd79d3c90c1f35ce0d5fda80d3e0..0e5dbd6cf5b5abd6dc6569972435b1bff23824e3 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2008-01-10  Raksit Ashok  <raksit@google.com>
+
+       PR rtl-optimization/27971
+       * combine.c (find_split_point): introduced a new split for certain
+       types of mem rtx.
+
 2008-01-10  DJ Delorie  <dj@redhat.com>
 
        * config/m32c/m32c.c (m32c_hard_regno_nregs_1): Renamed from...

diff --git a/gcc/combine.c b/gcc/combine.c
index b3d064d3f11b45ffd5c4e34f116be0dcdfd6b5d7..43623a4fbc4392732eed93fb50e24d0083086187 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -3967,6 +3967,15 @@ find_split_point (rtx *loc, rtx insn)
                         && OBJECT_P (SUBREG_REG (XEXP (XEXP (x, 0), 0)))))
            return &XEXP (XEXP (x, 0), 0);
        }
+
+      /* If we have a PLUS whose first operand is complex, try computing it
+         separately by making a split there.  */
+      if (GET_CODE (XEXP (x, 0)) == PLUS
+          && ! memory_address_p (GET_MODE (x), XEXP (x, 0))
+          && ! OBJECT_P (XEXP (XEXP (x, 0), 0))
+          && ! (GET_CODE (XEXP (XEXP (x, 0), 0)) == SUBREG
+                && OBJECT_P (SUBREG_REG (XEXP (XEXP (x, 0), 0)))))
+        return &XEXP (XEXP (x, 0), 0);
       break;
 
     case SET:

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 7546770c97bda9af69421e5b793bc42cef5b8bcd..1e1207b1bd64671056fd9e0facfad24c00223504 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2008-01-10  Raksit Ashok  <raksit@google.com>
+
+       PR rtl-optimization/27971
+       * gcc.target/i386/pr27971.c: New testcase.
+
 2008-01-10  Paul Thomas  <pault@gcc.gnu.org>
 
        PR fortran/34396

diff --git a/gcc/testsuite/gcc.target/i386/pr27971.c b/gcc/testsuite/gcc.target/i386/pr27971.c
new file mode 100644 (file)
index 0000000..8c706ad
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr27971.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+unsigned array[4];
+
+unsigned foo(unsigned long x)
+{
+          return array[(x>>2)&3ul];
+}
+
+/* { dg-final { scan-assembler-not "shr\[^\\n\]*2" } } */
+/* { dg-final { scan-assembler "and\[^\\n\]*12" } } */