[PATCH] Fix combine's make_extraction (PR rtl-optimization/78378)

[Jakub Jelinek]

Hi!

If inner is a MEM, make_extraction requires that pos is a multiple of bytes
and deals with offsetting it.  Or otherwise requires that pos is a multiple
of BITS_PER_WORD and for REG inner it handles that too.  But if inner
is something different, it calls just force_to_mode to the target mode,
which only really works if pos is 0.

Thus the following patch restricts it to that case.

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

2016-11-16  Jakub Jelinek  <ja...@redhat.com>

        PR rtl-optimization/78378
        * combine.c (make_extraction): Use force_to_mode for non-{REG,MEM}
        inner only if pos is 0.  Fix up formatting.

        * gcc.c-torture/execute/pr78378.c: New test.

--- gcc/combine.c.jj    2016-11-16 18:51:58.000000000 +0100
+++ gcc/combine.c       2016-11-16 19:52:12.735674000 +0100
@@ -7382,6 +7382,7 @@ make_extraction (machine_mode mode, rtx
   if (tmode != BLKmode
       && ((pos_rtx == 0 && (pos % BITS_PER_WORD) == 0
           && !MEM_P (inner)
+          && (pos == 0 || REG_P (inner))
           && (inner_mode == tmode
               || !REG_P (inner)
               || TRULY_NOOP_TRUNCATION_MODES_P (tmode, inner_mode)
@@ -7458,10 +7459,9 @@ make_extraction (machine_mode mode, rtx
        }
       else
        new_rtx = force_to_mode (inner, tmode,
-                            len >= HOST_BITS_PER_WIDE_INT
-                            ? HOST_WIDE_INT_M1U
-                            : (HOST_WIDE_INT_1U << len) - 1,
-                            0);
+                                len >= HOST_BITS_PER_WIDE_INT
+                                ? HOST_WIDE_INT_M1U
+                                : (HOST_WIDE_INT_1U << len) - 1, 0);
 
       /* If this extraction is going into the destination of a SET,
         make a STRICT_LOW_PART unless we made a MEM.  */
--- gcc/testsuite/gcc.c-torture/execute/pr78378.c.jj    2016-11-16 
20:02:16.975248597 +0100
+++ gcc/testsuite/gcc.c-torture/execute/pr78378.c       2016-11-16 
20:02:03.000000000 +0100
@@ -0,0 +1,18 @@
+/* PR rtl-optimization/78378 */
+
+unsigned long long __attribute__ ((noinline, noclone))
+foo (unsigned long long x)
+{
+  x <<= 41;
+  x /= 232;
+  return 1 + (unsigned short) x;
+}
+
+int
+main ()
+{
+  unsigned long long x = foo (1);
+  if (x != 0x2c24)
+    __builtin_abort();
+  return 0;
+}

        Jakub