VAX: Provide the `ctz' operation

Our `ffssi2_internal' pattern and the machine FFS instruction, which
technically is a bit-field operation, match the `ctz' operation exactly,
with the result produced for the bit-field source operand of zero equal
to its width as specified with another machine instruction operand, not
directly expressed in RTL and currently hardcoded in the assembly code
produced.  In our terms this is the bit size of the machine mode used,
and although it's SImode now let's be flexible for an upcoming change.

The operation also sets the Z condition code according to the value of
the source operand.

	gcc/
	* config/vax/builtins.md (ffssi2_internal): Rename insn to...
	(ctzsi2): ... this.  Update the RTL operation.
	(ffssi2): Update accordingly.
	* config/vax/vax.c (vax_notice_update_cc): Handle CTZ.
	* config/vax/vax.h (CTZ_DEFINED_VALUE_AT_ZERO): New macro.

	gcc/testsuite/
	* gcc.target/vax/ctzsi.c: New test.

diff --git a/gcc/config/vax/builtins.md b/gcc/config/vax/builtins.md
index 7e27854..e8cefe7 100644 (file)
--- a/gcc/config/vax/builtins.md
+++ b/gcc/config/vax/builtins.md
@@ -39,7 +39,7 @@
   rtx cond = gen_rtx_NE (VOIDmode, cc0_rtx, const0_rtx);
   rtx target = gen_rtx_IF_THEN_ELSE (VOIDmode, cond, label_ref, pc_rtx);
 
-  emit_insn (gen_ffssi2_internal (operands[0], operands[1]));
+  emit_insn (gen_ctzsi2 (operands[0], operands[1]));
   emit_jump_insn (gen_rtx_SET (pc_rtx, target));
   emit_insn (gen_negsi2 (operands[0], const1_rtx));
   emit_label (label);
@@ -47,9 +47,9 @@
   DONE;
 }")
 
-(define_insn "ffssi2_internal"
+(define_insn "ctzsi2"
   [(set (match_operand:SI 0 "nonimmediate_operand" "=rQ")
-       (ffs:SI (match_operand:SI 1 "general_operand" "nrQT")))
+       (ctz:SI (match_operand:SI 1 "general_operand" "nrQT")))
    (set (cc0)
        (compare (match_dup 1)
                 (const_int 0)))]

diff --git a/gcc/config/vax/vax.c b/gcc/config/vax/vax.c
index b6c2210..69a05b3 100644 (file)
--- a/gcc/config/vax/vax.c
+++ b/gcc/config/vax/vax.c
@@ -1135,6 +1135,9 @@ vax_notice_update_cc (rtx exp, rtx insn ATTRIBUTE_UNUSED)
            case REG:
              cc_status.flags = CC_NO_OVERFLOW;
              break;
+           case CTZ:
+             cc_status.flags = CC_NOT_NEGATIVE;
+             break;
            default:
              break;
            }

diff --git a/gcc/config/vax/vax.h b/gcc/config/vax/vax.h
index 146b0a6..43182ff 100644 (file)
--- a/gcc/config/vax/vax.h
+++ b/gcc/config/vax/vax.h
@@ -683,3 +683,7 @@ VAX operand formatting codes:
    by the proper FDE definition.  */
 #define INCOMING_RETURN_ADDR_RTX gen_rtx_REG (Pmode, PC_REGNUM)
 
+/* Upon failure to find the bit the FFS hardware instruction returns
+   the position of the bit immediately following the field specified.  */
+#define CTZ_DEFINED_VALUE_AT_ZERO(MODE, VALUE) \
+  ((VALUE) = GET_MODE_BITSIZE (MODE), 2)

diff --git a/gcc/testsuite/gcc.target/vax/ctzsi.c b/gcc/testsuite/gcc.target/vax/ctzsi.c
new file mode 100644 (file)
index 0000000..8be4271
--- /dev/null
+++ b/gcc/testsuite/gcc.target/vax/ctzsi.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+
+int
+ctzsi (unsigned int x)
+{
+  return __builtin_ctz (x);
+}
+
+/* Expect assembly like:
+
+       ffs $0,$32,4(%ap),%r0
+
+ */
+
+/* { dg-final { scan-assembler "\tffs \\\$0,\\\$32," } } */