Hi,

This is a gcc-9 backport of the PR97528 fix that has been applied to trunk and gcc-10.
Bootstraped on arm-linux-gnueabihf and regression tested.

OK for gcc-9 branch?

2021-02-02  Andre Vieira  <andre.simoesdiasvie...@arm.com>

    Backport from mainline
    2020-11-20  Jakub Jelinek  <ja...@redhat.com>

    PR target/97528
    * config/arm/arm.c (neon_vector_mem_operand): For POST_MODIFY, require
    first POST_MODIFY operand is a REG and is equal to the first operand
    of PLUS.

    * gcc.target/arm/pr97528.c: New test.

On 20/11/2020 11:25, Kyrylo Tkachov via Gcc-patches wrote:

-----Original Message-----
From: Jakub Jelinek <ja...@redhat.com>
Sent: 19 November 2020 18:57
To: Richard Earnshaw <richard.earns...@arm.com>; Ramana
Radhakrishnan <ramana.radhakrish...@arm.com>; Kyrylo Tkachov
<kyrylo.tkac...@arm.com>
Cc: gcc-patches@gcc.gnu.org
Subject: [PATCH] arm: Fix up neon_vector_mem_operand [PR97528]

Hi!

The documentation for POST_MODIFY says:
    Currently, the compiler can only handle second operands of the
    form (plus (reg) (reg)) and (plus (reg) (const_int)), where
    the first operand of the PLUS has to be the same register as
    the first operand of the *_MODIFY.
The following testcase ICEs, because combine just attempts to simplify
things and ends up with
(post_modify (reg1) (plus (mult (reg2) (const_int 4)) (reg1))
but the target predicates accept it, because they only verify
that POST_MODIFY's second operand is PLUS and the second operand
of the PLUS is a REG.

The following patch fixes this by performing further verification that
the POST_MODIFY is in the form it should be.

Bootstrapped/regtested on armv7hl-linux-gnueabi, ok for trunk
and release branches after a while?
Ok.
Thanks,
Kyrill

2020-11-19  Jakub Jelinek  <ja...@redhat.com>

        PR target/97528
        * config/arm/arm.c (neon_vector_mem_operand): For
POST_MODIFY, require
        first POST_MODIFY operand is a REG and is equal to the first operand
        of PLUS.

        * gcc.target/arm/pr97528.c: New test.

--- gcc/config/arm/arm.c.jj     2020-11-13 19:00:46.729620560 +0100
+++ gcc/config/arm/arm.c        2020-11-18 17:05:44.656867343 +0100
@@ -13429,7 +13429,9 @@ neon_vector_mem_operand (rtx op, int typ
    /* Allow post-increment by register for VLDn */
    if (type == 2 && GET_CODE (ind) == POST_MODIFY
        && GET_CODE (XEXP (ind, 1)) == PLUS
-      && REG_P (XEXP (XEXP (ind, 1), 1)))
+      && REG_P (XEXP (XEXP (ind, 1), 1))
+      && REG_P (XEXP (ind, 0))
+      && rtx_equal_p (XEXP (ind, 0), XEXP (XEXP (ind, 1), 0)))
       return true;

    /* Match:
--- gcc/testsuite/gcc.target/arm/pr97528.c.jj   2020-11-18
17:09:58.195053288 +0100
+++ gcc/testsuite/gcc.target/arm/pr97528.c      2020-11-18
17:09:47.839168237 +0100
@@ -0,0 +1,28 @@
+/* PR target/97528 */
+/* { dg-do compile } */
+/* { dg-require-effective-target arm_neon_ok } */
+/* { dg-options "-O1" }  */
+/* { dg-add-options arm_neon } */
+
+#include <arm_neon.h>
+
+typedef __simd64_int16_t T;
+typedef __simd64_uint16_t U;
+unsigned short c;
+int d;
+U e;
+
+void
+foo (void)
+{
+  unsigned short *dst = &c;
+  int g = d, b = 4;
+  U dc = e;
+  for (int h = 0; h < b; h++)
+    {
+      unsigned short *i = dst;
+      U j = dc;
+      vst1_s16 ((int16_t *) i, (T) j);
+      dst += g;
+    }
+}


        Jakub
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 
04edd637d43198ad801bb5ada8f1807faae7001e..4679da75dd823778d5a3e37c497ee10793e9c7d7
 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -12730,7 +12730,9 @@ neon_vector_mem_operand (rtx op, int type, bool strict)
   /* Allow post-increment by register for VLDn */
   if (type == 2 && GET_CODE (ind) == POST_MODIFY
       && GET_CODE (XEXP (ind, 1)) == PLUS
-      && REG_P (XEXP (XEXP (ind, 1), 1)))
+      && REG_P (XEXP (XEXP (ind, 1), 1))
+      && REG_P (XEXP (ind, 0))
+      && rtx_equal_p (XEXP (ind, 0), XEXP (XEXP (ind, 1), 0)))
      return true;
 
   /* Match:
diff --git a/gcc/testsuite/gcc.target/arm/pr97528.c 
b/gcc/testsuite/gcc.target/arm/pr97528.c
new file mode 100644
index 
0000000000000000000000000000000000000000..6cc59f2158c5f8c8dd78e5083ca7ebc4e5f63a44
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/pr97528.c
@@ -0,0 +1,28 @@
+/* PR target/97528 */
+/* { dg-do compile } */
+/* { dg-require-effective-target arm_neon_ok } */
+/* { dg-options "-O1" }  */
+/* { dg-add-options arm_neon } */
+
+#include <arm_neon.h>
+
+typedef __simd64_int16_t T;
+typedef __simd64_uint16_t U;
+unsigned short c;
+int d;
+U e;
+
+void
+foo (void)
+{
+  unsigned short *dst = &c;
+  int g = d, b = 4;
+  U dc = e;
+  for (int h = 0; h < b; h++)
+    {
+      unsigned short *i = dst;
+      U j = dc;
+      vst1_s16 ((int16_t *) i, (T) j);
+      dst += g;
+    }
+}

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