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PowerPC - optimize system initialization
- From: Gary Thomas <gary at mlbassoc dot com>
- To: eCos patches <ecos-patches at ecos dot sourceware dot org>
- Date: Fri, 12 Oct 2007 09:31:52 -0600
- Subject: PowerPC - optimize system initialization
... something I've thought about for a long time :-)
--
------------------------------------------------------------
Gary Thomas | Consulting for the
MLB Associates | Embedded world
------------------------------------------------------------
Index: hal/powerpc/arch/current/ChangeLog
===================================================================
RCS file: /misc/cvsfiles/ecos/packages/hal/powerpc/arch/current/ChangeLog,v
retrieving revision 1.69
diff -u -5 -p -r1.69 ChangeLog
--- hal/powerpc/arch/current/ChangeLog 18 Apr 2006 22:29:39 -0000 1.69
+++ hal/powerpc/arch/current/ChangeLog 12 Oct 2007 15:29:51 -0000
@@ -1,5 +1,9 @@
+2007-10-12 Gary Thomas <gary@mlbassoc.com>
+
+ * src/vectors.S: Optimize system initialization of DATA/BSS/etc.
+
2006-04-18 Gary Thomas <gary@mlbassoc.com>
* include/hal_arch.h: Adjust stack sizes - they were too small
(on machines with FPU) and didn't account for stack checking.
Index: hal/powerpc/arch/current/src/vectors.S
===================================================================
RCS file: /misc/cvsfiles/ecos/packages/hal/powerpc/arch/current/src/vectors.S,v
retrieving revision 1.32
diff -u -5 -p -r1.32 vectors.S
--- hal/powerpc/arch/current/src/vectors.S 8 Dec 2003 14:26:03 -0000 1.32
+++ hal/powerpc/arch/current/src/vectors.S 12 Oct 2007 15:29:08 -0000
@@ -301,14 +301,16 @@ _hal_hardware_init_done:
#if !defined(CYG_HAL_STARTUP_ROM) && defined(CYGSEM_HAL_POWERPC_COPY_VECTORS)
lwi r3,rom_vectors-4
lwi r4,((CYGHWR_HAL_POWERPC_VECTOR_BASE)-4)
lwi r5,rom_vectors_end-4
+ sub r5,r5,r3 # compute number of words to copy
+ srwi r5,r5,2
+ mtctr r5
0: lwzu r0,4(r3)
stwu r0,4(r4)
- cmplw r3,r5
- bne 0b
+ bdnz 0b
#endif
# set up stack
lwi sp,__interrupt_stack
mtspr SPRG0,sp # save in sprg0 for later use
@@ -316,52 +318,55 @@ _hal_hardware_init_done:
# Set up exception handlers and VSR table, taking care not to
# step on any ROM monitor''s toes.
hal_mon_init
#if defined(CYG_HAL_STARTUP_ROM)
-
# Copy data from ROM to ram
lwi r3,__rom_data_start # r3 = rom start
lwi r4,__ram_data_start # r4 = ram start
lwi r5,__ram_data_end # r5 = ram end
cmplw r4,r5 # skip if no data
beq 2f
-
-1:
- lwz r0,0(r3) # get word from ROM
- stw r0,0(r4) # store in RAM
- addi r3,r3,4 # increment by 1 word
- addi r4,r4,4 # increment by 1 word
- cmplw r4,r5 # compare
- blt 1b # loop if not yet done
+ sub r5,r5,r4 # compute number of words to copy
+ srwi r5,r5,2
+ mtctr r5
+ subi r3,r3,4
+ subi r4,r4,4
+1: lwzu r0,4(r3) # get word from ROM
+ stwu r0,4(r4) # store in RAM
+ bdnz 1b
2:
#endif
# clear BSS
lwi r3,__bss_start # r3 = start
lwi r4,__bss_end # r4 = end
li r0,0 # r0 = 0
cmplw r3,r4 # skip if no bss
beq 2f
+ sub r4,r4,r3 # compute number of words to clear
+ srwi r4,r4,2
+ mtctr r4
+ subi r3,r3,4
-1: stw r0,0(r3) # store zero
- addi r3,r3,4 # increment by 1 word
- cmplw r3,r4 # compare
- blt 1b # loop if not yet done
+1: stwu r0,4(r3) # store zero & increment pointer
+ bdnz 1b
2:
# clear SBSS
lwi r3,__sbss_start # r3 = start
lwi r4,__sbss_end # r4 = end
cmplw r3,r4 # skip if no sbss
beq 2f
+ sub r4,r4,r3 # compute number of words to clear
+ srwi r4,r4,2
+ mtctr r4
+ subi r3,r3,4
-1: stw r0,0(r3) # store zero
- addi r3,r3,4 # increment by 1 word
- cmplw r3,r4 # compare
- blt 1b # loop if not yet done
+1: stwu r0,4(r3) # store zero & increment pointer
+ bdnz 1b
2:
# It is now safe to call C functions which may rely on initialized
# data.