From d4e7de58116155e79272ea2b876a7c94115dbed1 Mon Sep 17 00:00:00 2001
From: Uros Bizjak <ubizjak@gmail.com>
Date: Thu, 19 Oct 2017 19:35:39 +0200
Subject: re PR target/82618 (Inefficient double-word subtraction on x86_64)

	PR target/82618
	* config/i386/i386.md (sub to cmp): New peephole2 pattern.

testsuite/ChangeLog:

	PR target/82618
	* gcc.target/i386/pr82618.c: New test.


Co-Authored-By: Jakub Jelinek <jakub@redhat.com>

From-SVN: r253905
---
 gcc/ChangeLog                           |  5 +++++
 gcc/config/i386/i386.md                 | 11 +++++++++++
 gcc/testsuite/ChangeLog                 |  6 ++++++
 gcc/testsuite/gcc.target/i386/pr82618.c | 18 ++++++++++++++++++
 4 files changed, 40 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr82618.c

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index c37cddb..b3740b5 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2017-10-19  Uros Bizjak  <ubizjak@gmail.com>
+
+	PR target/82618
+	* config/i386/i386.md (sub to cmp): New peephole2 pattern.
+
 2017-10-19  Alexander Monakov  <amonakov@ispras.ru>
 
 	PR rtl-optimization/82395
diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 6fed9b8..d909721 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -6766,6 +6766,17 @@
   [(set_attr "type" "alu")
    (set_attr "mode" "<MODE>")])
 
+(define_peephole2
+  [(parallel
+     [(set (reg:CC FLAGS_REG)
+	   (compare:CC (match_operand:SWI 0 "general_reg_operand")
+		       (match_operand:SWI 1 "general_gr_operand")))
+      (set (match_dup 0)
+	   (minus:SWI (match_dup 0) (match_dup 1)))])]
+  "find_regno_note (peep2_next_insn (0), REG_UNUSED, REGNO (operands[0])) != 0"
+  [(set (reg:CC FLAGS_REG)
+	(compare:CC (match_dup 0) (match_dup 1)))])
+
 (define_insn "*subsi_3_zext"
   [(set (reg FLAGS_REG)
 	(compare (match_operand:SI 1 "register_operand" "0")
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 31cf70b..8ef91aa 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2017-10-18  Uros Bizjak  <ubizjak@gmail.com>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	PR target/82618
+	* gcc.target/i386/pr82618.c: New test.
+
 2017-10-19  Martin Sebor  <msebor@redhat.com>
 
 	PR tree-optimization/82596
diff --git a/gcc/testsuite/gcc.target/i386/pr82618.c b/gcc/testsuite/gcc.target/i386/pr82618.c
new file mode 100644
index 0000000..f6e3589
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr82618.c
@@ -0,0 +1,18 @@
+/* PR target/82618 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+#ifdef __SIZEOF_INT128__
+typedef unsigned __int128 U;
+typedef unsigned long long H;
+#else
+typedef unsigned long long U;
+typedef unsigned int H;
+#endif
+
+H f0 (U x, U y)
+{
+  return (x - y) >> (__CHAR_BIT__ * sizeof (H));
+}
+
+/* { dg-final { scan-assembler {\mcmp} } } */
-- 
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