[ARM] PR rtl-optimization/69904: Disallow copying/duplicating of load-exclusive opera...

	PR rtl-optimization/69904
	* config/arm/arm.c (arm_cannot_copy_insn_p):
	Return true for load-exclusive instructions.

	* gcc.target/arm/pr69904.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@233941 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index fb5e396..9ae5500 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2016-03-03  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+       PR rtl-optimization/69904
+       * config/arm/arm.c (arm_cannot_copy_insn_p):
+       Return true for load-exclusive instructions.
+
 2016-03-03  Jakub Jelinek  <jakub@redhat.com>
 
        PR target/70021

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 9489343..c868490 100644 (file)
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -13263,7 +13263,11 @@ tls_mentioned_p (rtx x)
     }
 }
 
-/* Must not copy any rtx that uses a pc-relative address.  */
+/* Must not copy any rtx that uses a pc-relative address.
+   Also, disallow copying of load-exclusive instructions that
+   may appear after splitting of compare-and-swap-style operations
+   so as to prevent those loops from being transformed away from their
+   canonical forms (see PR 69904).  */
 
 static bool
 arm_cannot_copy_insn_p (rtx_insn *insn)
@@ -13282,6 +13286,20 @@ arm_cannot_copy_insn_p (rtx_insn *insn)
              || XINT (x, 1) == UNSPEC_PIC_UNIFIED))
        return true;
     }
+
+  rtx set = single_set (insn);
+  if (set)
+    {
+      rtx src = SET_SRC (set);
+      if (GET_CODE (src) == ZERO_EXTEND)
+       src = XEXP (src, 0);
+
+      /* Catch the load-exclusive and load-acquire operations.  */
+      if (GET_CODE (src) == UNSPEC_VOLATILE
+         && (XINT (src, 1) == VUNSPEC_LL
+             || XINT (src, 1) == VUNSPEC_LAX))
+       return true;
+    }
   return false;
 }
 

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 5ffe64f..a3592de 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-03-03  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+       PR rtl-optimization/69904
+       * gcc.target/arm/pr69904.c: New test.
+
 2016-03-03  Jakub Jelinek  <jakub@redhat.com>
 
        PR target/70021

diff --git a/gcc/testsuite/gcc.target/arm/pr69904.c b/gcc/testsuite/gcc.target/arm/pr69904.c
new file mode 100644 (file)
index 0000000..24fe844
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/pr69904.c
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -marm" } */
+/* { dg-require-effective-target arm_arch_v7a_ok } */
+/* { dg-add-options arm_arch_v7a } */
+
+/* Make sure that RTL optimizers don't do any unexpected transformations
+   on the compare_exchange loop.  */
+
+#include <stdatomic.h>
+
+atomic_uint foo;
+atomic_uint bar;
+int glob;
+
+int
+main (void)
+{
+  glob = atomic_compare_exchange_strong (&foo, &bar, 0);
+  return glob;
+}
+
+/* { dg-final { scan-assembler-times "dmb\tish" 2 } } */
+/* { dg-final { scan-assembler-times "ldrex\t" 1 } } */
+/* { dg-final { scan-assembler-times "strex\t" 1 } } */