From: Richard Biener <rguenther@suse.de>
Date: Tue, 20 Mar 2018 14:35:46 +0000 (+0000)
Subject: re PR target/84986 (Performance regression: loop no longer vectorized (x86-64))
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=b6c1e0329bb7c7b511d685ebb17ab4f2c515a75a;p=gcc.git

re PR target/84986 (Performance regression: loop no longer vectorized (x86-64))

2018-03-20  Richard Biener  <rguenther@suse.de>

	PR target/84986
	* config/i386/i386.c (ix86_add_stmt_cost): Only cost
	sign-conversions as zero, fall back to standard scalar_stmt
	cost for the rest.

	* gcc.dg/vect/costmodel/x86_64/costmodel-pr84986.c: New testcase.

From-SVN: r258684
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f47c1922f69..18d727e8ee3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2018-03-20  Richard Biener  <rguenther@suse.de>
+
+	PR target/84986
+	* config/i386/i386.c (ix86_add_stmt_cost): Only cost
+	sign-conversions as zero, fall back to standard scalar_stmt
+	cost for the rest.
+
 2018-03-20  Martin Liska  <mliska@suse.cz>
 
 	PR ipa/84825
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 5b1e962dedb..3b264318f50 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -50462,7 +50462,11 @@ ix86_add_stmt_cost (void *data, int count, enum vect_cost_for_stmt kind,
 	  }
 	  break;
 	case NOP_EXPR:
-	  stmt_cost = 0;
+	  /* Only sign-conversions are free.  */
+	  if (tree_nop_conversion_p
+	        (TREE_TYPE (gimple_assign_lhs (stmt_info->stmt)),
+		 TREE_TYPE (gimple_assign_rhs1 (stmt_info->stmt))))
+	    stmt_cost = 0;
 	  break;
 
 	case BIT_IOR_EXPR:
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 6c918c0065b..f88a09842fa 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-03-20  Richard Biener  <rguenther@suse.de>
+
+	PR target/84986
+	* gcc.dg/vect/costmodel/x86_64/costmodel-pr84986.c: New testcase.
+
 2018-03-20  Martin Liska  <mliska@suse.cz>
 
 	PR ipa/84825
diff --git a/gcc/testsuite/gcc.dg/vect/costmodel/x86_64/costmodel-pr84986.c b/gcc/testsuite/gcc.dg/vect/costmodel/x86_64/costmodel-pr84986.c
new file mode 100644
index 00000000000..b6dc385855e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/costmodel/x86_64/costmodel-pr84986.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target vect_long } */
+
+int N;
+long fn1(void) {
+  short i;
+  long a;
+  i = a = 0;
+  while (i < N)
+    a -= i++;
+  return a;
+}
+
+/* { dg-final { scan-tree-dump "vectorized 1 loops" "vect" } } */