From ad5bf450aef2ffee6d57ed193fabc5f72f8eaa65 Mon Sep 17 00:00:00 2001
From: rearnsha <rearnsha@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Thu, 19 Oct 2017 13:16:42 +0000
Subject: [PATCH] [ARM] PR 82445 - suppress 32-bit aligned ldrd/strd peepholing
 with -mno-unaligned-access

Peephole patterns exist in the arm backend to spot load/store
operations to adjacent memory operations in order to convert them into
ldrd/strd instructions.  However, when we have strict alignment
enforced, then we can only do this if the accesses are known to be
64-bit aligned; this is unlikely to be the case for most loads.  The
patch adds some alignment checking to the code that validates the
addresses for use in the peephole patterns.  This should also fix
incorrect generation of ldrd/strd with unaligned accesses that could
previously have occurred on ARMv5e where all such operations must be
64-bit aligned.

I've added some new tests as well.  In doing so I discovered that the
ldrd/strd peephole tests could never fail since they would match the
source file name in the scanned assembly as well as any instructions
of the intended type.  I've fixed those by tightening the scan results
slightly.

gcc:

* config/arm/arm.c (align_ok_ldrd_strd): New function.
(mem_ok_for_ldrd_strd): New parameter align.  Extract the alignment of the
mem into it.
(gen_operands_ldrd_strd): Validate the alignment of the accesses.

testsuite:

* gcc.target/arm/peep-ldrd-1.c: Tighten test scan pattern.
* gcc.target/arm/peep-strd-1.c: Likewise.
* gcc.target/arm/peep-ldrd-2.c: New test.
* gcc.target/arm/peep-strd-2.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-6-branch@253892 138bc75d-0d04-0410-961f-82ee72b054a4
---
Upstream-Status: Backport
Signed-off-by: Khem Raj <raj.khem@gmail.com>

 gcc/ChangeLog                                      |  8 +++++++
 gcc/config/arm/arm.c                               | 27 ++++++++++++++++++----
 gcc/testsuite/ChangeLog                            |  8 +++++++
 gcc/testsuite/gcc.target/arm/peep-ldrd-1.c         |  2 +-
 .../arm/{peep-ldrd-1.c => peep-ldrd-2.c}           |  4 ++--
 gcc/testsuite/gcc.target/arm/peep-strd-1.c         |  2 +-
 .../arm/{peep-strd-1.c => peep-strd-2.c}           |  4 ++--
 7 files changed, 44 insertions(+), 11 deletions(-)
 copy gcc/testsuite/gcc.target/arm/{peep-ldrd-1.c => peep-ldrd-2.c} (63%)
 copy gcc/testsuite/gcc.target/arm/{peep-strd-1.c => peep-strd-2.c} (58%)

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 9c0813d598d..e3da9f77fb6 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -15926,12 +15926,23 @@ operands_ok_ldrd_strd (rtx rt, rtx rt2, rtx rn, HOST_WIDE_INT offset,
   return true;
 }
 
+/* Return true if a 64-bit access with alignment ALIGN and with a
+   constant offset OFFSET from the base pointer is permitted on this
+   architecture.  */
+static bool
+align_ok_ldrd_strd (HOST_WIDE_INT align, HOST_WIDE_INT offset)
+{
+  return (unaligned_access
+	  ? (align >= BITS_PER_WORD && (offset & 3) == 0)
+	  : (align >= 2 * BITS_PER_WORD && (offset & 7) == 0));
+}
+
 /* Helper for gen_operands_ldrd_strd.  Returns true iff the memory
    operand MEM's address contains an immediate offset from the base
-   register and has no side effects, in which case it sets BASE and
-   OFFSET accordingly.  */
+   register and has no side effects, in which case it sets BASE,
+   OFFSET and ALIGN accordingly.  */
 static bool
-mem_ok_for_ldrd_strd (rtx mem, rtx *base, rtx *offset)
+mem_ok_for_ldrd_strd (rtx mem, rtx *base, rtx *offset, HOST_WIDE_INT *align)
 {
   rtx addr;
 
@@ -15950,6 +15961,7 @@ mem_ok_for_ldrd_strd (rtx mem, rtx *base, rtx *offset)
   gcc_assert (MEM_P (mem));
 
   *offset = const0_rtx;
+  *align = MEM_ALIGN (mem);
 
   addr = XEXP (mem, 0);
 
@@ -15990,7 +16002,7 @@ gen_operands_ldrd_strd (rtx *operands, bool load,
                         bool const_store, bool commute)
 {
   int nops = 2;
-  HOST_WIDE_INT offsets[2], offset;
+  HOST_WIDE_INT offsets[2], offset, align[2];
   rtx base = NULL_RTX;
   rtx cur_base, cur_offset, tmp;
   int i, gap;
@@ -16002,7 +16014,8 @@ gen_operands_ldrd_strd (rtx *operands, bool load,
      registers, and the corresponding memory offsets.  */
   for (i = 0; i < nops; i++)
     {
-      if (!mem_ok_for_ldrd_strd (operands[nops+i], &cur_base, &cur_offset))
+      if (!mem_ok_for_ldrd_strd (operands[nops+i], &cur_base, &cur_offset,
+				 &align[i]))
         return false;
 
       if (i == 0)
@@ -16114,6 +16127,7 @@ gen_operands_ldrd_strd (rtx *operands, bool load,
       /* Swap the instructions such that lower memory is accessed first.  */
       std::swap (operands[0], operands[1]);
       std::swap (operands[2], operands[3]);
+      std::swap (align[0], align[1]);
       if (const_store)
         std::swap (operands[4], operands[5]);
     }
@@ -16127,6 +16141,9 @@ gen_operands_ldrd_strd (rtx *operands, bool load,
   if (gap != 4)
     return false;
 
+  if (!align_ok_ldrd_strd (align[0], offset))
+    return false;
+
   /* Make sure we generate legal instructions.  */
   if (operands_ok_ldrd_strd (operands[0], operands[1], base, offset,
                              false, load))
diff --git a/gcc/testsuite/gcc.target/arm/peep-ldrd-1.c b/gcc/testsuite/gcc.target/arm/peep-ldrd-1.c
index eb2b86ee7b6..d49eff6b87e 100644
--- a/gcc/testsuite/gcc.target/arm/peep-ldrd-1.c
+++ b/gcc/testsuite/gcc.target/arm/peep-ldrd-1.c
@@ -8,4 +8,4 @@ int foo(int a, int b, int* p, int *q)
   *p = a;
   return a;
 }
-/* { dg-final { scan-assembler "ldrd" } } */
+/* { dg-final { scan-assembler "ldrd\\t" } } */
diff --git a/gcc/testsuite/gcc.target/arm/peep-ldrd-1.c b/gcc/testsuite/gcc.target/arm/peep-ldrd-2.c
similarity index 63%
copy from gcc/testsuite/gcc.target/arm/peep-ldrd-1.c
copy to gcc/testsuite/gcc.target/arm/peep-ldrd-2.c
index eb2b86ee7b6..6822c2b1454 100644
--- a/gcc/testsuite/gcc.target/arm/peep-ldrd-1.c
+++ b/gcc/testsuite/gcc.target/arm/peep-ldrd-2.c
@@ -1,6 +1,6 @@
 /* { dg-do compile } */
 /* { dg-require-effective-target arm_prefer_ldrd_strd } */
-/* { dg-options "-O2" }  */
+/* { dg-options "-O2 -mno-unaligned-access" }  */
 int foo(int a, int b, int* p, int *q)
 {
   a = p[2] + p[3];
@@ -8,4 +8,4 @@ int foo(int a, int b, int* p, int *q)
   *p = a;
   return a;
 }
-/* { dg-final { scan-assembler "ldrd" } } */
+/* { dg-final { scan-assembler-not "ldrd\\t" } } */
diff --git a/gcc/testsuite/gcc.target/arm/peep-strd-1.c b/gcc/testsuite/gcc.target/arm/peep-strd-1.c
index bd330769599..fe1beac7229 100644
--- a/gcc/testsuite/gcc.target/arm/peep-strd-1.c
+++ b/gcc/testsuite/gcc.target/arm/peep-strd-1.c
@@ -6,4 +6,4 @@ void foo(int a, int b, int* p)
   p[2] = a;
   p[3] = b;
 }
-/* { dg-final { scan-assembler "strd" } } */
+/* { dg-final { scan-assembler "strd\\t" } } */
diff --git a/gcc/testsuite/gcc.target/arm/peep-strd-1.c b/gcc/testsuite/gcc.target/arm/peep-strd-2.c
similarity index 58%
copy from gcc/testsuite/gcc.target/arm/peep-strd-1.c
copy to gcc/testsuite/gcc.target/arm/peep-strd-2.c
index bd330769599..bfc5ebe9eec 100644
--- a/gcc/testsuite/gcc.target/arm/peep-strd-1.c
+++ b/gcc/testsuite/gcc.target/arm/peep-strd-2.c
@@ -1,9 +1,9 @@
 /* { dg-do compile } */
 /* { dg-require-effective-target arm_prefer_ldrd_strd } */
-/* { dg-options "-O2" }  */
+/* { dg-options "-O2 -mno-unaligned-access" }  */
 void foo(int a, int b, int* p)
 {
   p[2] = a;
   p[3] = b;
 }
-/* { dg-final { scan-assembler "strd" } } */
+/* { dg-final { scan-assembler-not "strd\\t" } } */
-- 
2.15.0