combine: Take known zero bits into account when checking extraction.

gcc/ChangeLog:

	* combine.c (make_compound_operation): Take known zero bits into
	account when checking for possible zero_extend.

gcc/testsuite/ChangeLog:

	* gcc.dg/zero_bits_compound-1.c: New test.
	* gcc.dg/zero_bits_compound-2.c: New test.

From-SVN: r236813

5 files changed, 119 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2d59cb5..59aa6d1 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2016-05-27  Dominik Vogt  <vogt@linux.vnet.ibm.com>
+
+	* combine.c (make_compound_operation): Take known zero bits into
+	account when checking for possible zero_extend.
+
 2016-05-27  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
 	* config/aarch64/aarch64.md (ashl<mode>3, SHORT modes):
diff --git a/gcc/combine.c b/gcc/combine.c
index cd864cc..4db11b0 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -7988,6 +7988,34 @@ make_compound_operation (rtx x, enum rtx_code in_code)
 							next_code),
 			       i, NULL_RTX, 1, 1, 0, 1);
 
+      /* If the one operand is a paradoxical subreg of a register or memory and
+	 the constant (limited to the smaller mode) has only zero bits where
+	 the sub expression has known zero bits, this can be expressed as
+	 a zero_extend.  */
+      else if (GET_CODE (XEXP (x, 0)) == SUBREG)
+	{
+	  rtx sub;
+
+	  sub = XEXP (XEXP (x, 0), 0);
+	  machine_mode sub_mode = GET_MODE (sub);
+	  if ((REG_P (sub) || MEM_P (sub))
+	      && GET_MODE_PRECISION (sub_mode) < mode_width)
+	    {
+	      unsigned HOST_WIDE_INT mode_mask = GET_MODE_MASK (sub_mode);
+	      unsigned HOST_WIDE_INT mask;
+
+	      /* original AND constant with all the known zero bits set */
+	      mask = UINTVAL (XEXP (x, 1)) | (~nonzero_bits (sub, sub_mode));
+	      if ((mask & mode_mask) == mode_mask)
+		{
+		  new_rtx = make_compound_operation (sub, next_code);
+		  new_rtx = make_extraction (mode, new_rtx, 0, 0,
+					     GET_MODE_PRECISION (sub_mode),
+					     1, 0, in_code == COMPARE);
+		}
+	    }
+	}
+
       break;
 
     case LSHIFTRT:
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a959325..c209d98 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-05-27  Dominik Vogt  <vogt@linux.vnet.ibm.com>
+
+	* gcc.dg/zero_bits_compound-1.c: New test.
+	* gcc.dg/zero_bits_compound-2.c: New test.
+
 2016-05-27  Ilya Enkovich  <ilya.enkovich@intel.com>
 
 	PR middle-end/71279
diff --git a/gcc/testsuite/gcc.dg/zero_bits_compound-1.c b/gcc/testsuite/gcc.dg/zero_bits_compound-1.c
new file mode 100644
index 0000000..d78dc43
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/zero_bits_compound-1.c
@@ -0,0 +1,42 @@
+/* Test whether an AND mask or'ed with the know zero bits that equals a mode
+   mask is a candidate for zero extendion.  */
+
+/* Note: This test requires that char, int and long have different sizes and the
+   target has a way to do 32 -> 64 bit zero extension other than AND.  */
+
+/* { dg-do compile { target x86_64-*-* s390*-*-* } } */
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-O3 -dP" } */
+
+unsigned long foo (unsigned char c)
+{
+  unsigned long l;
+  unsigned int i;
+
+  i = ((unsigned int)c) << 8;
+  i |= ((unsigned int)c) << 20;
+  asm volatile ("":::);
+  i = i & 0x0ff0ff00;
+  asm volatile ("":::);
+  l = (unsigned long)i;
+
+  return l;
+}
+
+unsigned long bar (unsigned char c)
+{
+  unsigned long l;
+  unsigned int i;
+
+  i = ((unsigned int)c) << 8;
+  i |= ((unsigned int)c) << 20;
+  asm volatile ("":::);
+  i = i & 0x0ffffff0;
+  asm volatile ("":::);
+  l = (unsigned long)i;
+
+  return l;
+}
+
+/* Check that no pattern containing an AND expression was used.  */
+/* { dg-final { scan-assembler-not "\\(and:" } } */
diff --git a/gcc/testsuite/gcc.dg/zero_bits_compound-2.c b/gcc/testsuite/gcc.dg/zero_bits_compound-2.c
new file mode 100644
index 0000000..80fd363
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/zero_bits_compound-2.c
@@ -0,0 +1,39 @@
+/* Test whether an AND mask or'ed with the know zero bits that equals a mode
+   mask is a candidate for zero extendion.  */
+
+/* { dg-do compile { target x86_64-*-* s390*-*-* } } */
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-O3 -dP" } */
+
+unsigned long foo (unsigned char c)
+{
+  unsigned long l;
+  unsigned int i;
+
+  i = ((unsigned int)c) << 8;
+  i |= ((unsigned int)c) << 20;
+  asm volatile ("":::);
+  i = i & 0x0fe0fe00;
+  asm volatile ("":::);
+  l = (unsigned long)i;
+
+  return l;
+}
+
+unsigned long bar (unsigned char c)
+{
+  unsigned long l;
+  unsigned int i;
+
+  i = ((unsigned int)c) << 8;
+  i |= ((unsigned int)c) << 20;
+  asm volatile ("":::);
+  i = i & 0x07f007f0;
+  asm volatile ("":::);
+  l = (unsigned long)i;
+
+  return l;
+}
+
+/* Check that an AND expression was used.  */
+/* { dg-final { scan-assembler-times "\\(and:" 2 } } */