Add abs pattern to handle {si,di} mode abs to avoid pmax/cmove conversion.

2019-12-17  Hongyu Wang  <hongyu.wang@intel.com>

gcc/
	PR target/92651
	* config/i386/i386.h (TARGET_EXPAND_ABS): New macro.
	* config/i386/x86-tune.def (X86_TUNE_EXPAND_ABS): New.
	* config/i386/i386.md (abs<SWI48x>2): New define_expand.

gcc/testsuite
	* gcc.target/i386/pr92651.c: New testcase.

From-SVN: r279452

6 files changed, 75 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 9a37d82..bd1a252 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2019-12-17  Hongyu Wang  <hongyu.wang@intel.com>
+
+	PR target/92651
+	* config/i386/i386.h (TARGET_EXPAND_ABS): New macro.
+	* config/i386/x86-tune.def (X86_TUNE_EXPAND_ABS): New.
+	* config/i386/i386.md (abs<SWI48x>2): New define_expand.
+
 2019-12-17  H.J. Lu  <hjl.tools@gmail.com>
 
 	PR target/92807
diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index 2542cb3..65f6c76 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -596,6 +596,8 @@ extern unsigned char ix86_tune_features[X86_TUNE_LAST];
 	ix86_tune_features[X86_TUNE_USE_XCHG_FOR_ATOMIC_STORE]
 #define TARGET_EMIT_VZEROUPPER \
 	ix86_tune_features[X86_TUNE_EMIT_VZEROUPPER]
+#define TARGET_EXPAND_ABS \
+	ix86_tune_features[X86_TUNE_EXPAND_ABS]
 
 /* Feature tests against the various architecture variations.  */
 enum ix86_arch_indices {
diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 66a6f20..cf4a0cc 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -9669,6 +9669,45 @@
   "#"
   [(set_attr "isa" "noavx,noavx,avx,avx")])
 
+;; Special expand pattern to handle integer mode abs
+
+(define_expand "abs<mode>2"
+  [(set (match_operand:SWI48x 0 "register_operand")
+    (abs:SWI48x
+      (match_operand:SWI48x 1 "register_operand")))]
+  "TARGET_EXPAND_ABS"
+  {
+    machine_mode mode = <MODE>mode;
+
+    /* Generate rtx abs using abs (x) = (((signed) x >> (W-1)) ^ x) -
+       ((signed) x >> (W-1)) */
+    rtx shift_amount = gen_int_shift_amount (mode,
+				       GET_MODE_PRECISION (mode)
+				       - 1);
+    shift_amount = convert_modes (E_QImode, GET_MODE (shift_amount),
+			    shift_amount, 1);
+    rtx shift_dst = gen_reg_rtx (mode);
+    rtx shift_op = gen_rtx_SET (shift_dst,
+			  gen_rtx_fmt_ee (ASHIFTRT, mode,
+					  operands[1], shift_amount));
+    rtx clobber = gen_rtx_CLOBBER (VOIDmode, gen_rtx_REG (CCmode,
+						    FLAGS_REG));
+    emit_insn (gen_rtx_PARALLEL (VOIDmode, gen_rtvec (2, shift_op,
+						clobber)));
+
+    rtx xor_op = gen_rtx_SET (operands[0],
+			gen_rtx_fmt_ee (XOR, mode, shift_dst,
+					operands[1]));
+    emit_insn (gen_rtx_PARALLEL (VOIDmode, gen_rtvec (2, xor_op, clobber)));
+
+    rtx minus_op = gen_rtx_SET (operands[0],
+			  gen_rtx_fmt_ee (MINUS, mode,
+					  operands[0], shift_dst));
+    emit_insn (gen_rtx_PARALLEL (VOIDmode, gen_rtvec (2, minus_op,
+						clobber)));
+    DONE;
+  })
+
 (define_expand "<code><mode>2"
   [(set (match_operand:X87MODEF 0 "register_operand")
 	(absneg:X87MODEF (match_operand:X87MODEF 1 "register_operand")))]
diff --git a/gcc/config/i386/x86-tune.def b/gcc/config/i386/x86-tune.def
index 328535d..58a81e5 100644
--- a/gcc/config/i386/x86-tune.def
+++ b/gcc/config/i386/x86-tune.def
@@ -317,6 +317,13 @@ DEF_TUNE (X86_TUNE_ONE_IF_CONV_INSN, "one_if_conv_insn",
 DEF_TUNE (X86_TUNE_USE_XCHG_FOR_ATOMIC_STORE, "use_xchg_for_atomic_store",
 	 m_CORE_ALL | m_BDVER | m_ZNVER | m_GENERIC)
 
+/* X86_TUNE_EXPAND_ABS: This enables a new abs pattern by
+   generating instructions for abs (x) = (((signed) x >> (W-1) ^ x) -
+   (signed) x >> (W-1)) instead of cmove or SSE max/abs instructions.  */
+DEF_TUNE (X86_TUNE_EXPAND_ABS, "expand_abs",
+	  m_CORE_ALL | m_SILVERMONT | m_KNL | m_KNM | m_GOLDMONT
+	  | m_GOLDMONT_PLUS | m_TREMONT )
+
 /*****************************************************************************/
 /* 387 instruction selection tuning                                          */
 /*****************************************************************************/
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 4142c50..5fff39e 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2019-12-17  Hongyu Wang  <hongyu.wang@intel.com>
+
+	* gcc.target/i386/pr92651.c: New testcase.
+
 2019-12-17  H.J. Lu  <hjl.tools@gmail.com>
 
 	PR target/92807
diff --git a/gcc/testsuite/gcc.target/i386/pr92651.c b/gcc/testsuite/gcc.target/i386/pr92651.c
new file mode 100644
index 0000000..3d0c3c7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr92651.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=corei7" } */
+
+#include <stdlib.h>
+
+int foo(unsigned char a, unsigned char b)
+{
+    int isum=abs(a - b);
+    return isum;
+}
+
+/* { dg-final { scan-assembler-not "cmov*" } } */
+/* { dg-final { scan-assembler "(cltd|cdq|shr)" } } */
+/* { dg-final { scan-assembler-times "xor" 1 } } */
+/* { dg-final { scan-assembler-times "sub" 2 } } */
+