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RFC: Turn on -fomit-frame-pointer and -fasynchronous-unwind-tables for Linux/i386


Hi,

This patch turns on -fomit-frame-pointer and -fasynchronous-unwind-tables
for Linux/i386.  Tested on Linux/ia32 and Linux/x86-64.  I am also
enclosing a spreadsheet of comparison of shared library segment sizes
in gcc.  Segment size differences range from -1% to 30%. The smaller
the DSO size is, the bigger its size increases. Overall, the size
difference is close to 0%. This comparison may not be typical since
C++ and Java libraries have .eh_frame sections anyway.  Any comments?

Thanks.



H.J.
---
gcc/

2010-07-14  H.J. Lu  <hongjiu.lu@intel.com>

	* config/i386/i386.c (override_options): Default
	flag_omit_frame_pointer and flag_asynchronous_unwind_tables
	to TARGET_SUBTARGET32_OMIT_FRAME_POINTER_DEFAULT and
	TARGET_SUBTARGET32_ASYNCHRONOUS_UNWIND_TABLES_DEFAULT.

	* config/i386/i386.h (TARGET_SUBTARGET32_OMIT_FRAME_POINTER_DEFAULT):
	New.
	(TARGET_SUBTARGET32_ASYNCHRONOUS_UNWIND_TABLES_DEFAULT): Likewise.
	* config/i386/linux.h (TARGET_SUBTARGET32_OMIT_FRAME_POINTER_DEFAULT):
	Likewise.
	(TARGET_SUBTARGET32_ASYNCHRONOUS_UNWIND_TABLES_DEFAULT): Likewise.
	* config/i386/linux64.h (TARGET_SUBTARGET32_OMIT_FRAME_POINTER_DEFAULT):
	Likewise.
	(TARGET_SUBTARGET32_ASYNCHRONOUS_UNWIND_TABLES_DEFAULT): Likewise.

gcc/testsuite/

2010-07-15  H.J. Lu  <hongjiu.lu@intel.com>

	* gcc.target/i386/frame-pointer-1.c: New.
	* gcc.target/i386/frame-pointer-2.c: Likewise.
	* gcc.target/i386/frame-pointer-3.c: Likewise.
	* gcc.target/i386/frame-pointer-4.c: Likewise.

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 4fd2aab..fe30bfd 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -2985,10 +2985,23 @@ override_options (bool main_args_p)
     {
       if (flag_zee == 2)
         flag_zee = 0;
+      /* Unwind info is not correct around the CFG unless either a
+	 frame pointer is present or -maccumulate-outgoing-args is
+	 set. When both -fasynchronous-unwind-tables and
+	 -fomit-frame-pointer are turned on by default, turn off
+	 both if -mno-accumulate-outgoing-args is used.  */
       if (flag_omit_frame_pointer == 2)
-	flag_omit_frame_pointer = 0;
+	flag_omit_frame_pointer
+	  = (TARGET_SUBTARGET32_OMIT_FRAME_POINTER_DEFAULT
+	     && (!TARGET_SUBTARGET32_ASYNCHRONOUS_UNWIND_TABLES_DEFAULT
+		 || !(target_flags_explicit
+		      & MASK_ACCUMULATE_OUTGOING_ARGS)));
       if (flag_asynchronous_unwind_tables == 2)
-	flag_asynchronous_unwind_tables = 0;
+	flag_asynchronous_unwind_tables
+	  = (TARGET_SUBTARGET32_ASYNCHRONOUS_UNWIND_TABLES_DEFAULT
+	     && (!TARGET_SUBTARGET32_OMIT_FRAME_POINTER_DEFAULT
+		 || !(target_flags_explicit
+		      & MASK_ACCUMULATE_OUTGOING_ARGS)));
       if (flag_pcc_struct_return == 2)
 	flag_pcc_struct_return = DEFAULT_PCC_STRUCT_RETURN;
     }
diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index eb3eb9f..c0ae95f 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -467,6 +467,8 @@ extern tree x86_mfence;
 /* Extra bits to force on w/ 32-bit mode.  */
 #define TARGET_SUBTARGET32_DEFAULT 0
 #define TARGET_SUBTARGET32_ISA_DEFAULT 0
+#define TARGET_SUBTARGET32_OMIT_FRAME_POINTER_DEFAULT 0
+#define TARGET_SUBTARGET32_ASYNCHRONOUS_UNWIND_TABLES_DEFAULT 0
 
 /* Extra bits to force on w/ 64-bit mode.  */
 #define TARGET_SUBTARGET64_DEFAULT 0
diff --git a/gcc/config/i386/linux.h b/gcc/config/i386/linux.h
index 81dfd1e..61d53b5 100644
--- a/gcc/config/i386/linux.h
+++ b/gcc/config/i386/linux.h
@@ -219,3 +219,10 @@ along with GCC; see the file COPYING3.  If not see
 /* i386 glibc provides __stack_chk_guard in %gs:0x14.  */
 #define TARGET_THREAD_SSP_OFFSET	0x14
 #endif
+
+/* Turn on -fomit-frame-pointer and -fasynchronous-unwind-tables by
+   default.  */
+#undef TARGET_SUBTARGET32_OMIT_FRAME_POINTER_DEFAULT
+#define TARGET_SUBTARGET32_OMIT_FRAME_POINTER_DEFAULT 1
+#undef TARGET_SUBTARGET32_ASYNCHRONOUS_UNWIND_TABLES_DEFAULT
+#define TARGET_SUBTARGET32_ASYNCHRONOUS_UNWIND_TABLES_DEFAULT 1
diff --git a/gcc/config/i386/linux64.h b/gcc/config/i386/linux64.h
index 33b4dc9..5a02205 100644
--- a/gcc/config/i386/linux64.h
+++ b/gcc/config/i386/linux64.h
@@ -123,3 +123,10 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
    x86_64 glibc provides it in %fs:0x28.  */
 #define TARGET_THREAD_SSP_OFFSET	(TARGET_64BIT ? 0x28 : 0x14)
 #endif
+
+/* Turn on -fomit-frame-pointer and -fasynchronous-unwind-tables by
+   default.  */
+#undef TARGET_SUBTARGET32_OMIT_FRAME_POINTER_DEFAULT
+#define TARGET_SUBTARGET32_OMIT_FRAME_POINTER_DEFAULT 1
+#undef TARGET_SUBTARGET32_ASYNCHRONOUS_UNWIND_TABLES_DEFAULT
+#define TARGET_SUBTARGET32_ASYNCHRONOUS_UNWIND_TABLES_DEFAULT 1
diff --git a/gcc/testsuite/gcc.target/i386/frame-pointer-1.c b/gcc/testsuite/gcc.target/i386/frame-pointer-1.c
new file mode 100644
index 0000000..2495d09
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/frame-pointer-1.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mtune=i686" } */
+/* { dg-require-effective-target ilp32 } */
+
+void bar (int);
+
+void
+foo (void)
+{
+  bar (1);
+}
diff --git a/gcc/testsuite/gcc.target/i386/frame-pointer-2.c b/gcc/testsuite/gcc.target/i386/frame-pointer-2.c
new file mode 100644
index 0000000..1478aba
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/frame-pointer-2.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mtune=i686 -mno-accumulate-outgoing-args" } */
+/* { dg-require-effective-target ilp32 } */
+
+void bar (int);
+
+void
+foo (void)
+{
+  bar (1);
+}
diff --git a/gcc/testsuite/gcc.target/i386/frame-pointer-3.c b/gcc/testsuite/gcc.target/i386/frame-pointer-3.c
new file mode 100644
index 0000000..2ff965f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/frame-pointer-3.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mtune=i686 -mpush-args" } */
+/* { dg-require-effective-target ilp32 } */
+
+void bar (int);
+
+void
+foo (void)
+{
+  bar (1);
+}
diff --git a/gcc/testsuite/gcc.target/i386/frame-pointer-4.c b/gcc/testsuite/gcc.target/i386/frame-pointer-4.c
new file mode 100644
index 0000000..2b1bf52
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/frame-pointer-4.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mtune=i686 -mpush-args -mno-accumulate-outgoing-args" } */
+/* { dg-require-effective-target ilp32 } */
+
+void bar (int);
+
+void
+foo (void)
+{
+  bar (1);
+}

Attachment: gcc frame pointer.xlsx
Description: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet


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