[PATCH] i386: Restore Skylake SImode hard register store cost

[PATCH] i386: Restore Skylake SImode hard register store cost

[H.J. Lu]

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On Skylake, we should move integer register to SSE register without
going through memory.  This patch restores Skylake SImode hard register
store cost to 6.

gcc/

PR target/90878
* config/i386/x86-tune-costs.h (skylake_cost): Restore SImode
hard register store cost to 6.

gcc/testsuite/

PR target/90878
* gcc.target/i386/pr90878.c: New test.

OK for trunk?

Thanks.

-- 
H.J.

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From 827748528f5418fb3d28d4f023bd158e7951d33c Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Wed, 14 Aug 2019 19:42:52 -0700
Subject: [PATCH] i386: Restore Skylake SImode hard register store cost

On Skylake, we should move integer register to SSE register without
going through memory.  This patch restores Skylake SImode hard register
store cost to 6.

gcc/

	PR target/90878
	* config/i386/x86-tune-costs.h (skylake_cost): Restore SImode
	hard register store cost to 6.

gcc/testsuite/

	PR target/90878
	* gcc.target/i386/pr90878.c: New test.
---
 gcc/config/i386/x86-tune-costs.h        |  2 +-
 gcc/testsuite/gcc.target/i386/pr90878.c | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr90878.c

diff --git a/gcc/config/i386/x86-tune-costs.h b/gcc/config/i386/x86-tune-costs.h
index 00edece3eb68..7a2c7c55b4cc 100644
--- a/gcc/config/i386/x86-tune-costs.h
+++ b/gcc/config/i386/x86-tune-costs.h
@@ -1594,7 +1594,7 @@ struct processor_costs skylake_cost = {
   {4, 4, 4},				/* cost of loading integer registers
 					   in QImode, HImode and SImode.
 					   Relative to reg-reg move (2).  */
-  {6, 6, 3},				/* cost of storing integer registers */
+  {6, 6, 6},				/* cost of storing integer registers */
   2,					/* cost of reg,reg fld/fst */
   {6, 6, 8},				/* cost of loading fp registers
 					   in SFmode, DFmode and XFmode */
diff --git a/gcc/testsuite/gcc.target/i386/pr90878.c b/gcc/testsuite/gcc.target/i386/pr90878.c
new file mode 100644
index 000000000000..18dd64bdaa7a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr90878.c
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=skylake" } */
+
+union ieee754_float
+  {
+    float f;
+
+    struct
+      {
+	unsigned int mantissa:23;
+	unsigned int exponent:8;
+	unsigned int negative:1;
+      } ieee;
+};
+
+double
+foo (float f)
+{
+  union ieee754_float u;
+  u.f = f;
+  u.ieee.negative = 0;
+  return u.f;
+}
+
+/* { dg-final { scan-assembler-not "vcvtss2sd\[^\\n\]*\\\(%.sp\\\)" } } */
-- 
2.20.1

Re: [PATCH] i386: Restore Skylake SImode hard register store cost

[Uros Bizjak]

On Wed, Sep 18, 2019 at 8:06 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Skylake, we should move integer register to SSE register without
> going through memory.  This patch restores Skylake SImode hard register
> store cost to 6.
>
> gcc/
>
> PR target/90878
> * config/i386/x86-tune-costs.h (skylake_cost): Restore SImode
> hard register store cost to 6.
>
> gcc/testsuite/
>
> PR target/90878
> * gcc.target/i386/pr90878.c: New test.
>
> OK for trunk?

OK, as with your previous patch.

Thanks,
Uros.