[PATCH, rs6000] Enable vector compare for 16-byte memory equality compare [PR111449]

[HAO CHEN GUI <guihaoc@linux.ibm.com>]

Hi,
  This patch enables vector compare for 16-byte memory equality compare.
The 16-byte memory equality compare can be efficiently implemented by
instruction "vcmpequb." It reduces one branch and one compare compared
with two 8-byte compare sequence.

  16-byte vector compare is not enabled on 32bit sub-targets as TImode
hasn't been supported well on 32bit sub-targets.

  Bootstrapped and tested on powerpc64-linux BE and LE with no regressions.

Thanks
Gui Haochen

ChangeLog
rs6000: Enable vector compare for 16-byte memory equality compare

gcc/
	PR target/111449
	* config/rs6000/altivec.md (cbranchti4): New expand pattern.
	* config/rs6000/rs6000.cc (rs6000_generate_compare): Generate insn
	sequence for TImode vector equality compare.
	* config/rs6000/rs6000.h (MOVE_MAX_PIECES): Define.
	(COMPARE_MAX_PIECES): Define.

gcc/testsuite/
	PR target/111449
	* gcc.target/powerpc/pr111449.c: New.

patch.diff
diff --git a/gcc/config/rs6000/altivec.md b/gcc/config/rs6000/altivec.md
index e8a596fb7e9..99264235cbe 100644
--- a/gcc/config/rs6000/altivec.md
+++ b/gcc/config/rs6000/altivec.md
@@ -2605,6 +2605,24 @@ (define_insn "altivec_vupklpx"
 }
   [(set_attr "type" "vecperm")])

+(define_expand "cbranchti4"
+  [(use (match_operator 0 "equality_operator"
+	[(match_operand:TI 1 "memory_operand")
+	 (match_operand:TI 2 "memory_operand")]))
+   (use (match_operand 3))]
+  "VECTOR_UNIT_ALTIVEC_P (V16QImode)"
+{
+  rtx op1 = simplify_subreg (V16QImode, operands[1], TImode, 0);
+  rtx op2 = simplify_subreg (V16QImode, operands[2], TImode, 0);
+  operands[1] = force_reg (V16QImode, op1);
+  operands[2] = force_reg (V16QImode, op2);
+  rtx_code code = GET_CODE (operands[0]);
+  operands[0] = gen_rtx_fmt_ee (code, V16QImode, operands[1],
+				operands[2]);
+  rs6000_emit_cbranch (TImode, operands);
+  DONE;
+})
+
 ;; Compare vectors producing a vector result and a predicate, setting CR6 to
 ;; indicate a combined status
 (define_insn "altivec_vcmpequ<VI_char>_p"
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index efe9adce1f8..c6b935a64e7 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -15264,6 +15264,15 @@ rs6000_generate_compare (rtx cmp, machine_mode mode)
 	  else
 	    emit_insn (gen_stack_protect_testsi (compare_result, op0, op1b));
 	}
+      else if (mode == TImode)
+	{
+	  gcc_assert (code == EQ || code == NE);
+
+	  rtx result_vector = gen_reg_rtx (V16QImode);
+	  compare_result = gen_rtx_REG (CCmode, CR6_REGNO);
+	  emit_insn (gen_altivec_vcmpequb_p (result_vector, op0, op1));
+	  code = (code == NE) ? GE : LT;
+	}
       else
 	emit_insn (gen_rtx_SET (compare_result,
 				gen_rtx_COMPARE (comp_mode, op0, op1)));
diff --git a/gcc/config/rs6000/rs6000.h b/gcc/config/rs6000/rs6000.h
index 3503614efbd..dc33bca0802 100644
--- a/gcc/config/rs6000/rs6000.h
+++ b/gcc/config/rs6000/rs6000.h
@@ -1730,6 +1730,8 @@ typedef struct rs6000_args
    in one reasonably fast instruction.  */
 #define MOVE_MAX (! TARGET_POWERPC64 ? 4 : 8)
 #define MAX_MOVE_MAX 8
+#define MOVE_MAX_PIECES (!TARGET_POWERPC64 ? 4 : 16)
+#define COMPARE_MAX_PIECES (!TARGET_POWERPC64 ? 4 : 16)

 /* Nonzero if access to memory by bytes is no faster than for words.
    Also nonzero if doing byte operations (specifically shifts) in registers
diff --git a/gcc/testsuite/gcc.target/powerpc/pr111449.c b/gcc/testsuite/gcc.target/powerpc/pr111449.c
new file mode 100644
index 00000000000..ab9583f47bb
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr111449.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target powerpc_p8vector_ok } */
+/* { dg-options "-maltivec -O2" } */
+/* { dg-require-effective-target has_arch_ppc64 } */
+
+/* Ensure vector comparison is used for 16-byte memory equality compare.  */
+
+int compare (const char* s1, const char* s2)
+{
+  return __builtin_memcmp (s1, s2, 16) == 0;
+}
+
+/* { dg-final { scan-assembler-times {\mvcmpequb\M} 1 } } */
+/* { dg-final { scan-assembler-not {\mcmpd\M} } } */