arm.c (arm_option_override): Set MASK_SINGLE_PIC_BASE when -mno-pic-data-is-text-relative is in effect...

	gcc/
	* config/arm/arm.c (arm_option_override): Set MASK_SINGLE_PIC_BASE
	when -mno-pic-data-is-text-relative is in effect, by default.
	* doc/invoke.texi (mpic-data-is-text-relative): Document new
	behavior and clarify.

	gcc/testsuite/
	* gcc.target/arm/data-rel-1.c: New.
	* gcc.target/arm/data-rel-2.c: New.
	* gcc.target/arm/data-rel-3.c: New.

From-SVN: r238254

5 files changed, 54 insertions, 7 deletions

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 2394a17..6af0d36 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -3346,6 +3346,20 @@ arm_option_override (void)
 	}
     }
 
+  if (TARGET_VXWORKS_RTP)
+    {
+      if (!global_options_set.x_arm_pic_data_is_text_relative)
+	arm_pic_data_is_text_relative = 0;
+    }
+  else if (flag_pic
+	   && !arm_pic_data_is_text_relative
+	   && !(global_options_set.x_target_flags & MASK_SINGLE_PIC_BASE))
+    /* When text & data segments don't have a fixed displacement, the
+       intended use is with a single, read only, pic base register.
+       Unless the user explicitly requested not to do that, set
+       it.  */
+    target_flags |= MASK_SINGLE_PIC_BASE;
+
   /* If stack checking is disabled, we can use r10 as the PIC register,
      which keeps r9 available.  The EABI specifies r9 as the PIC register.  */
   if (flag_pic && TARGET_SINGLE_PIC_BASE)
@@ -3377,10 +3391,6 @@ arm_option_override (void)
 	arm_pic_register = pic_register;
     }
 
-  if (TARGET_VXWORKS_RTP
-      && !global_options_set.x_arm_pic_data_is_text_relative)
-    arm_pic_data_is_text_relative = 0;
-
   /* Enable -mfix-cortex-m3-ldrd by default for Cortex-M3 cores.  */
   if (fix_cm3_ldrd == 2)
     {
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 88fff05..9a4db38 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -14369,9 +14369,12 @@ otherwise the default is @samp{R10}.
 
 @item -mpic-data-is-text-relative
 @opindex mpic-data-is-text-relative
-Assume that each data segments are relative to text segment at load time.
-Therefore, it permits addressing data using PC-relative operations.
-This option is on by default for targets other than VxWorks RTP.
+Assume that the displacement between the text and data segments is fixed
+at static link time.  This permits using PC-relative addressing
+operations to access data known to be in the data segment.  For
+non-VxWorks RTP targets, this option is enabled by default.  When
+disabled on such targets, it will enable @option{-msingle-pic-base} by
+default.
 
 @item -mpoke-function-name
 @opindex mpoke-function-name
diff --git a/gcc/testsuite/gcc.target/arm/data-rel-1.c b/gcc/testsuite/gcc.target/arm/data-rel-1.c
new file mode 100644
index 0000000..d9d88f2
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/data-rel-1.c
@@ -0,0 +1,12 @@
+/* { dg-options "-fPIC -mno-pic-data-is-text-relative" } */
+/* { dg-final { scan-assembler-not "j-\\(.LPIC"  } } */
+/* { dg-final { scan-assembler-not "_GLOBAL_OFFSET_TABLE_-\\(.LPIC" } } */
+/* { dg-final { scan-assembler "j\\(GOT\\)" } } */
+/* { dg-final { scan-assembler "(ldr|mov)\tr\[0-9\]+, \\\[?r9" } } */
+
+static int j;
+
+int *Foo ()
+{
+  return &j;
+}
diff --git a/gcc/testsuite/gcc.target/arm/data-rel-2.c b/gcc/testsuite/gcc.target/arm/data-rel-2.c
new file mode 100644
index 0000000..6ba47d6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/data-rel-2.c
@@ -0,0 +1,11 @@
+/* { dg-options "-fPIC -mno-pic-data-is-text-relative -mno-single-pic-base" } */
+/* { dg-final { scan-assembler-not "j-\\(.LPIC"  } } */
+/* { dg-final { scan-assembler "_GLOBAL_OFFSET_TABLE_-\\(.LPIC" } } */
+/* { dg-final { scan-assembler "j\\(GOT\\)" } } */
+
+static int j;
+
+int *Foo ()
+{
+  return &j;
+}
diff --git a/gcc/testsuite/gcc.target/arm/data-rel-3.c b/gcc/testsuite/gcc.target/arm/data-rel-3.c
new file mode 100644
index 0000000..2ce1e66
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/data-rel-3.c
@@ -0,0 +1,11 @@
+/* { dg-options "-fPIC -mpic-data-is-text-relative" } */
+/* { dg-final { scan-assembler "j-\\(.LPIC"  } } */
+/* { dg-final { scan-assembler-not "_GLOBAL_OFFSET_TABLE_-\\(.LPIC" } } */
+/* { dg-final { scan-assembler-not "j\\(GOT\\)" } } */
+
+static int j;
+
+int *Foo ()
+{
+  return &j;
+}