MIPS: Enable dead code elimination

Select CONFIG_HAVE_LD_DEAD_CODE_DATA_ELIMINATION for MIPS, allowing the
user to enable dead code elimination. In order for this to work, ensure
that we keep the data bus exception table & the machine list by
annotating them with KEEP.

This shrinks both 32r2el_defconfig & 64r6el_defconfig builds by ~6%, as
shown by numbers from scripts/bloat-o-meter:

          | 32r2el_defconfig | 64r6el_defconfig
  --------|------------------|------------------
   No DCE | 8919864          | 8286307
      DCE | 8338988 (-6.51%) | 7741808 (-6.57%)

Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/21187/
Cc: linux-mips@linux-mips.org

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
index 971a504001c2..cb7e9ed7a453 100644
--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -72,7 +72,7 @@ SECTIONS
 	/* Exception table for data bus errors */
 	__dbe_table : {
 		__start___dbe_table = .;
-		*(__dbe_table)
+		KEEP(*(__dbe_table))
 		__stop___dbe_table = .;
 	}
 
@@ -123,7 +123,7 @@ SECTIONS
 	. = ALIGN(4);
 	.mips.machines.init : AT(ADDR(.mips.machines.init) - LOAD_OFFSET) {
 		__mips_machines_start = .;
-		*(.mips.machines.init)
+		KEEP(*(.mips.machines.init))
 		__mips_machines_end = .;
 	}