re PR rtl-optimization/67028 (combine bug. Different assumptions about subreg in...

	PR rtl-optimization/67028
	* combine.c (simplify_comparison): Fix comment.  Rearrange code.
	Add test to see if a const_int fits in the new mode.

gcc/testsuite/
	PR rtl-optimization/67028
	* gcc.dg/pr67028.c: New testcase.

From-SVN: r226731

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 00070d94dfad2feeb8214a943137e4ee051373bf..c85c8e3adbe357eb55afef0ae7ac66da962d46f9 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2015-08-08  Segher Boessenkool  <segher@kernel.crashing.org>
+
+       PR rtl-optimization/67028
+       * combine.c (simplify_comparison): Fix comment.  Rearrange code.
+       Add test to see if a const_int fits in the new mode.
+
 2015-08-07  DJ Delorie  <dj@redhat.com>
 
        * config/rx/rx.c (rx_mode_dependent_address_p): Remove unneeded asserts.

diff --git a/gcc/combine.c b/gcc/combine.c
index 4a92f55c8a0bfb44bb735fb5e1ab73aa7d80a6fe..8f98cbb6bdfccf08336ac0b84309475d0a40901a 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -12057,14 +12057,15 @@ simplify_comparison (enum rtx_code code, rtx *pop0, rtx *pop1)
              continue;
            }
 
-         /* If this is (and:M1 (subreg:M2 X 0) (const_int C1)) where C1
+         /* If this is (and:M1 (subreg:M1 X:M2 0) (const_int C1)) where C1
             fits in both M1 and M2 and the SUBREG is either paradoxical
             or represents the low part, permute the SUBREG and the AND
             and try again.  */
-         if (GET_CODE (XEXP (op0, 0)) == SUBREG)
+         if (GET_CODE (XEXP (op0, 0)) == SUBREG
+             && CONST_INT_P (XEXP (op0, 1)))
            {
-             unsigned HOST_WIDE_INT c1;
              tmode = GET_MODE (SUBREG_REG (XEXP (op0, 0)));
+             unsigned HOST_WIDE_INT c1 = INTVAL (XEXP (op0, 1));
              /* Require an integral mode, to avoid creating something like
                 (AND:SF ...).  */
              if (SCALAR_INT_MODE_P (tmode)
@@ -12074,16 +12075,20 @@ simplify_comparison (enum rtx_code code, rtx *pop0, rtx *pop1)
                     have a defined value due to the AND operation.
                     However, if we commute the AND inside the SUBREG then
                     they no longer have defined values and the meaning of
-                    the code has been changed.  */
+                    the code has been changed.
+                    Also C1 should not change value in the smaller mode,
+                    see PR67028 (a positive C1 can become negative in the
+                    smaller mode, so that the AND does no longer mask the
+                    upper bits).  */
                  && ((WORD_REGISTER_OPERATIONS
                       && mode_width > GET_MODE_PRECISION (tmode)
-                      && mode_width <= BITS_PER_WORD)
+                      && mode_width <= BITS_PER_WORD
+                      && trunc_int_for_mode (c1, tmode) == (HOST_WIDE_INT) c1)
                      || (mode_width <= GET_MODE_PRECISION (tmode)
                          && subreg_lowpart_p (XEXP (op0, 0))))
-                 && CONST_INT_P (XEXP (op0, 1))
                  && mode_width <= HOST_BITS_PER_WIDE_INT
                  && HWI_COMPUTABLE_MODE_P (tmode)
-                 && ((c1 = INTVAL (XEXP (op0, 1))) & ~mask) == 0
+                 && (c1 & ~mask) == 0
                  && (c1 & ~GET_MODE_MASK (tmode)) == 0
                  && c1 != mask
                  && c1 != GET_MODE_MASK (tmode))

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 8aba7c0351d496d4274cc47f3891350106df7e4d..38b6f9ee49bc2c744afad0857d3b6d7ad4558259 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2015-08-08  Segher Boessenkool  <segher@kernel.crashing.org>
+
+       PR rtl-optimization/67028
+       * gcc.dg/pr67028.c: New testcase.
+
 2015-08-07  H.J. Lu  <hongjiu.lu@intel.com>
 
        PR rtl-optimization/67029

diff --git a/gcc/testsuite/gcc.dg/pr67028.c b/gcc/testsuite/gcc.dg/pr67028.c
new file mode 100644 (file)
index 0000000..b42fb81
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr67028.c
@@ -0,0 +1,21 @@
+/* { dg-do run } */
+/* { dg-options "-O3" } */
+
+short c = 0;
+
+int __attribute__ ((noinline)) f(void)
+{
+       int d = 5;
+       signed char e = (c != 1) * -2;
+       int a = (unsigned short)e > d;
+
+       return a;
+}
+
+int main(void)
+{
+       if (!f())
+               __builtin_abort();
+
+       return 0;
+}