re PR target/15184 (Direct access to byte inside word not working with -march=pentiumpro)

	PR target/15184
	* combine.c (try_combine): If I0 is a memory load and I3 a store
	to a related address, increase the "goodness" of doing a 4-insn
	combination with I0-I3.
	(make_field_assignment): Handle SUBREGs in the ior+and case.

	PR target/15184
	* gcc.target/i386/pr15184-1.c: New test.
	* gcc.target/i386/pr15184-2.c: New test.

From-SVN: r220249

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 7424d9faa42cb7e2da21b11d419e3813ad05f0cc..0c02d43ff2ebe9936fd12dfe9983690090eb9fc8 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2015-01-29  Jeff Law  <law@redhat.com>
+
+       PR target/15184 
+       * combine.c (try_combine): If I0 is a memory load and I3 a store
+       to a related address, increase the "goodness" of doing a 4-insn
+       combination with I0-I3.
+       (make_field_assignment): Handle SUBREGs in the ior+and case.
+
 2015-01-29  Yuri Rumyantsev  <ysrumyan@gmail.com>
 
        PR tree-optimization/64746

diff --git a/gcc/combine.c b/gcc/combine.c
index 5c763b4a1d5c3f5680708d4e81baac3972437925..24418df002f7ce4c3683d19d586a6bccd1cf9259 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -2620,6 +2620,7 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
       int i;
       int ngood = 0;
       int nshift = 0;
+      rtx set0, set3;
 
       if (!flag_expensive_optimizations)
        return 0;
@@ -2643,6 +2644,34 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
                   || GET_CODE (src) == LSHIFTRT)
            nshift++;
        }
+
+      /* If I0 loads a memory and I3 sets the same memory, then I2 and I3
+        are likely manipulating its value.  Ideally we'll be able to combine
+        all four insns into a bitfield insertion of some kind. 
+
+        Note the source in I0 might be inside a sign/zero extension and the
+        memory modes in I0 and I3 might be different.  So extract the address
+        from the destination of I3 and search for it in the source of I0.
+
+        In the event that there's a match but the source/dest do not actually
+        refer to the same memory, the worst that happens is we try some
+        combinations that we wouldn't have otherwise.  */
+      if ((set0 = single_set (i0))
+         /* Ensure the source of SET0 is a MEM, possibly buried inside
+            an extension.  */
+         && (GET_CODE (SET_SRC (set0)) == MEM
+             || ((GET_CODE (SET_SRC (set0)) == ZERO_EXTEND
+                  || GET_CODE (SET_SRC (set0)) == SIGN_EXTEND)
+                 && GET_CODE (XEXP (SET_SRC (set0), 0)) == MEM))
+         && (set3 = single_set (i3))
+         /* Ensure the destination of SET3 is a MEM.  */
+         && GET_CODE (SET_DEST (set3)) == MEM
+         /* Would it be better to extract the base address for the MEM
+            in SET3 and look for that?  I don't have cases where it matters
+            but I could envision such cases.  */
+         && rtx_referenced_p (XEXP (SET_DEST (set3), 0), SET_SRC (set0)))
+       ngood += 2;
+
       if (ngood < 2 && nshift < 2)
        return 0;
     }
@@ -9272,6 +9301,13 @@ make_field_assignment (rtx x)
      to the appropriate position, force it to the required mode, and
      make the extraction.  Check for the AND in both operands.  */
 
+  /* One or more SUBREGs might obscure the constant-position field
+     assignment.  The first one we are likely to encounter is an outer
+     narrowing SUBREG, which we can just strip for the purposes of
+     identifying the constant-field assignment.  */
+  if (GET_CODE (src) == SUBREG && subreg_lowpart_p (src))
+    src = SUBREG_REG (src);
+
   if (GET_CODE (src) != IOR && GET_CODE (src) != XOR)
     return x;
 
@@ -9282,10 +9318,38 @@ make_field_assignment (rtx x)
       && CONST_INT_P (XEXP (rhs, 1))
       && rtx_equal_for_field_assignment_p (XEXP (rhs, 0), dest))
     c1 = INTVAL (XEXP (rhs, 1)), other = lhs;
+  /* The second SUBREG that might get in the way is a paradoxical
+     SUBREG around the first operand of the AND.  We want to 
+     pretend the operand is as wide as the destination here.   We
+     do this by creating a new MEM in the wider mode for the sole
+     purpose of the call to rtx_equal_for_field_assignment_p.   Also
+     note this trick only works for MEMs.  */
+  else if (GET_CODE (rhs) == AND
+          && paradoxical_subreg_p (XEXP (rhs, 0))
+          && GET_CODE (SUBREG_REG (XEXP (rhs, 0))) == MEM
+          && CONST_INT_P (XEXP (rhs, 1))
+          && rtx_equal_for_field_assignment_p (gen_rtx_MEM (GET_MODE (dest),
+                                                            XEXP (SUBREG_REG (XEXP (rhs, 0)), 0)),
+                                               dest))
+    c1 = INTVAL (XEXP (rhs, 1)), other = lhs;
   else if (GET_CODE (lhs) == AND
           && CONST_INT_P (XEXP (lhs, 1))
           && rtx_equal_for_field_assignment_p (XEXP (lhs, 0), dest))
     c1 = INTVAL (XEXP (lhs, 1)), other = rhs;
+  /* The second SUBREG that might get in the way is a paradoxical
+     SUBREG around the first operand of the AND.  We want to 
+     pretend the operand is as wide as the destination here.   We
+     do this by creating a new MEM in the wider mode for the sole
+     purpose of the call to rtx_equal_for_field_assignment_p.   Also
+     note this trick only works for MEMs.  */
+  else if (GET_CODE (lhs) == AND
+          && paradoxical_subreg_p (XEXP (lhs, 0))
+          && GET_CODE (SUBREG_REG (XEXP (lhs, 0))) == MEM
+          && CONST_INT_P (XEXP (lhs, 1))
+          && rtx_equal_for_field_assignment_p (gen_rtx_MEM (GET_MODE (dest),
+                                                            XEXP (SUBREG_REG (XEXP (lhs, 0)), 0)),
+                                               dest))
+    c1 = INTVAL (XEXP (lhs, 1)), other = rhs;
   else
     return x;
 

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 69488ec0106a01c2aa7fb5c02cf7957aaa9affec..c60230f00dadc181c2945c7bd776c383b335a4b9 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2015-01-29  Jeff Law  <law@redhat.com>
+
+       PR target/15184
+       * gcc.target/i386/pr15184-1.c: New test.
+       * gcc.target/i386/pr15184-2.c: New test.
+
 2015-01-29  Yuri Rumyantsev  <ysrumyan@gmail.com>
 
        PR tree-optimization/64746

diff --git a/gcc/testsuite/gcc.target/i386/pr15184-1.c b/gcc/testsuite/gcc.target/i386/pr15184-1.c
new file mode 100644 (file)
index 0000000..9eb544c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr15184-1.c
@@ -0,0 +1,33 @@
+/* PR 15184 first two tests, plus two addition ones.  */
+/* { dg-do compile } */
+/* { dg-options "-O2 -m32 -march=pentiumpro" } */
+
+#define regparm __attribute__((__regparm__(3)))
+
+extern unsigned int x;
+extern unsigned short y;
+
+void regparm f0(unsigned char c)
+{
+       x = (x & 0xFFFFFF00) | (unsigned int)c;
+}
+
+void regparm f1(unsigned char c)
+{
+     x = (x & 0xFFFF00FF) | ((unsigned int)c << 8);
+}
+
+void regparm f2(unsigned char c)
+{
+     x = (x & 0xFF00FFFF) | ((unsigned int)c << 16);
+}
+void regparm f3(unsigned char c)
+{
+     x = (x & 0x00FFFFFF) | ((unsigned int)c << 24);
+}
+
+
+/* Each function should compile down to a byte move from
+   the input register into x, possibly at an offset within x.  */
+/* { dg-final { scan-assembler-times "\tmovb\t%al, x" 4 } } */
+

diff --git a/gcc/testsuite/gcc.target/i386/pr15184-2.c b/gcc/testsuite/gcc.target/i386/pr15184-2.c
new file mode 100644 (file)
index 0000000..99fdbc8
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr15184-2.c
@@ -0,0 +1,23 @@
+/* PR 15184 second two tests
+/* { dg-do compile } */
+/* { dg-options "-O2 -m32 -march=pentiumpro" } */
+
+#define regparm __attribute__((__regparm__(3)))
+
+extern unsigned int x;
+extern unsigned short y;
+
+void regparm g0(unsigned char c)
+{
+        y = (y & 0xFF00) | (unsigned short)c;
+}
+
+void regparm g1(unsigned char c)
+{
+        y = (y & 0x00FF) | ((unsigned short)c << 8);
+}
+
+/* Each function should compile down to a byte move from
+   the input register into x, possibly at an offset within x.  */
+/* { dg-final { scan-assembler-times "\tmovb\t%al, y" 2 } } */
+