On Wed, Jan 27, 2016 at 7:34 AM, Ilya Enkovich <[email protected]> wrote:
> Hi,
>
> Currently STV pass may require a stack realignment if any
> transformation occurs to enable SSE registers spill/fill.
> It appears it's invalid to increase stack alignment requirements
> at this point. Thus we have to either assume we need stack to be
> aligned if are going to run STV pass or disable STV if stack is
> not properly aligned. I suppose we shouldn't ignore explicitly
> requested stack alignment not beeing sure we really optimize
> anything (and STV is not an optimization frequiently applied).
> So I think we may disable TARGET_STV for such cases as Jakub
> suggested. This patch was bootstrapped and regtested on
> x86_64-pc-linux-gnu. OK for trunk?
>
> diff --git a/gcc/testsuite/gcc.target/i386/pr69454-1.c
> b/gcc/testsuite/gcc.target/i386/pr69454-1.c
> new file mode 100644
> index 0000000..12ecfd3
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr69454-1.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile { target { ia32 } } } */
> +/* { dg-options "-O2 -msse2 -mno-accumulate-outgoing-args
> -mpreferred-stack-boundary=2" } */
> +
> +typedef struct { long long w64[2]; } V128;
> +extern V128* fn2(void);
> +long long a;
> +V128 b;
> +void fn1() {
> + V128 *c = fn2();
> + c->w64[0] = a ^ b.w64[0];
> +}
> diff --git a/gcc/testsuite/gcc.target/i386/pr69454-2.c
> b/gcc/testsuite/gcc.target/i386/pr69454-2.c
> new file mode 100644
> index 0000000..28bab93
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr69454-2.c
> @@ -0,0 +1,13 @@
> +/* { dg-do compile { target { ia32 } } } */
> +/* { dg-options "-O2 -mpreferred-stack-boundary=2" } */
This needs:
+/* { dg-options "-O2 -msse2 -mno-accumulate-outgoing-args
-mpreferred-stack-boundary=2" } */
to trigger.
> +extern void fn2 ();
> +long long a, b;
> +
> +void fn1 ()
> +{
> + long long c = a;
> + a = b ^ a;
> + fn2 ();
> + a = c;
> +}
Here is a different patch, which I believe is the right fix.
--
H.J.
From 86e040399dd5ca6b23597be4aff5edb9ac2ab5d7 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <[email protected]>
Date: Mon, 25 Jan 2016 12:31:45 -0800
Subject: [PATCH] Don't align DImode to 32 bits if the STV pass is enabled
Since the STV pass uses SSE2 instructions on DImode which needs 64-bit
alignment for DImode, don't align DImode to 32 bits if the STV pass is
enabled.
gcc/
PR target/69454
* config/i386/i386.c (convert_scalars_to_vector): Don't change
stack alignment here.
(ix86_minimum_alignment): Don't align DImode to 32 bits if the
STV pass is enabled.
gcc/testsuite/
PR target/69454
* gcc.target/i386/pr69454-1.c: New test.
* gcc.target/i386/pr69454-2.c: Likewise.
---
gcc/config/i386/i386.c | 16 ++++------------
gcc/testsuite/gcc.target/i386/pr69454-1.c | 11 +++++++++++
gcc/testsuite/gcc.target/i386/pr69454-2.c | 13 +++++++++++++
3 files changed, 28 insertions(+), 12 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/i386/pr69454-1.c
create mode 100644 gcc/testsuite/gcc.target/i386/pr69454-2.c
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index cfbdf0f..8babdaf 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -3588,16 +3588,6 @@ convert_scalars_to_vector ()
bitmap_obstack_release (NULL);
df_process_deferred_rescans ();
- /* Conversion means we may have 128bit register spills/fills
- which require aligned stack. */
- if (converted_insns)
- {
- if (crtl->stack_alignment_needed < 128)
- crtl->stack_alignment_needed = 128;
- if (crtl->stack_alignment_estimated < 128)
- crtl->stack_alignment_estimated = 128;
- }
-
return 0;
}
@@ -29299,8 +29289,10 @@ ix86_minimum_alignment (tree exp, machine_mode mode,
return align;
/* Don't do dynamic stack realignment for long long objects with
- -mpreferred-stack-boundary=2. */
- if ((mode == DImode || (type && TYPE_MODE (type) == DImode))
+ -mpreferred-stack-boundary=2. The STV pass uses SSE2 instructions
+ on DImode which needs 64-bit alignment for DImode. */
+ if (!(TARGET_STV && TARGET_SSE2 && optimize > 1)
+ && (mode == DImode || (type && TYPE_MODE (type) == DImode))
&& (!type || !TYPE_USER_ALIGN (type))
&& (!decl || !DECL_USER_ALIGN (decl)))
return 32;
diff --git a/gcc/testsuite/gcc.target/i386/pr69454-1.c b/gcc/testsuite/gcc.target/i386/pr69454-1.c
new file mode 100644
index 0000000..12ecfd3
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr69454-1.c
@@ -0,0 +1,11 @@
+/* { dg-do compile { target { ia32 } } } */
+/* { dg-options "-O2 -msse2 -mno-accumulate-outgoing-args -mpreferred-stack-boundary=2" } */
+
+typedef struct { long long w64[2]; } V128;
+extern V128* fn2(void);
+long long a;
+V128 b;
+void fn1() {
+ V128 *c = fn2();
+ c->w64[0] = a ^ b.w64[0];
+}
diff --git a/gcc/testsuite/gcc.target/i386/pr69454-2.c b/gcc/testsuite/gcc.target/i386/pr69454-2.c
new file mode 100644
index 0000000..4820b76
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr69454-2.c
@@ -0,0 +1,13 @@
+/* { dg-do compile { target { ia32 } } } */
+/* { dg-options "-O2 -msse2 -mno-accumulate-outgoing-args -mpreferred-stack-boundary=2" } */
+
+extern void fn2 (void);
+long long a, b;
+void
+fn1 (void)
+{
+ long long c = a;
+ a = b ^ a;
+ fn2 ();
+ a = c;
+}
--
2.5.0
