Revert "ARM: 7668/1: fix memset-related crashes caused by recent GCC …

…(4.7.2) optimizations"

This reverts commit 690c641.

There have been various reports of FAT partition corruption following this commit. Reverting for now to see if things improve.

arch/arm/lib/memset.S

@@ -19,24 +19,20 @@
 1: subs r2, r2, #4 @ 1 do we have enough
  blt 5f @ 1 bytes to align with?
  cmp r3, #2 @ 1
- strltb r1, [ip], #1 @ 1
- strleb r1, [ip], #1 @ 1
- strb r1, [ip], #1 @ 1
+ strltb r1, [r0], #1 @ 1
+ strleb r1, [r0], #1 @ 1
+ strb r1, [r0], #1 @ 1
  add r2, r2, r3 @ 1 (r2 = r2 - (4 - r3))
 /*
  * The pointer is now aligned and the length is adjusted. Try doing the
  * memset again.
  */
 
 ENTRY(memset)
-/*
- * Preserve the contents of r0 for the return value.
- */
- mov ip, r0
- ands r3, ip, #3 @ 1 unaligned?
+ ands r3, r0, #3 @ 1 unaligned?
  bne 1b @ 1
 /*
- * we know that the pointer in ip is aligned to a word boundary.
+ * we know that the pointer in r0 is aligned to a word boundary.
  */
  orr r1, r1, r1, lsl #8
  orr r1, r1, r1, lsl #16
@@ -47,28 +43,29 @@ ENTRY(memset)
 #if ! CALGN(1)+0
 
 /*
- * We need 2 extra registers for this loop - use r8 and the LR
+ * We need an extra register for this loop - save the return address and
+ * use the LR
  */
- stmfd sp!, {r8, lr}
- mov r8, r1
+ str lr, [sp, #-4]!
+ mov ip, r1
  mov lr, r1
 
 2: subs r2, r2, #64
- stmgeia ip!, {r1, r3, r8, lr} @ 64 bytes at a time.
- stmgeia ip!, {r1, r3, r8, lr}
- stmgeia ip!, {r1, r3, r8, lr}
- stmgeia ip!, {r1, r3, r8, lr}
+ stmgeia r0!, {r1, r3, ip, lr} @ 64 bytes at a time.
+ stmgeia r0!, {r1, r3, ip, lr}
+ stmgeia r0!, {r1, r3, ip, lr}
+ stmgeia r0!, {r1, r3, ip, lr}
  bgt 2b
- ldmeqfd sp!, {r8, pc} @ Now <64 bytes to go.
+ ldmeqfd sp!, {pc} @ Now <64 bytes to go.
 /*
  * No need to correct the count; we're only testing bits from now on
  */
  tst r2, #32
- stmneia ip!, {r1, r3, r8, lr}
- stmneia ip!, {r1, r3, r8, lr}
+ stmneia r0!, {r1, r3, ip, lr}
+ stmneia r0!, {r1, r3, ip, lr}
  tst r2, #16
- stmneia ip!, {r1, r3, r8, lr}
- ldmfd sp!, {r8, lr}
+ stmneia r0!, {r1, r3, ip, lr}
+ ldr lr, [sp], #4
 
 #else
 
@@ -77,54 +74,54 @@ ENTRY(memset)
  * whole cache lines at once.
  */
 
- stmfd sp!, {r4-r8, lr}
+ stmfd sp!, {r4-r7, lr}
  mov r4, r1
  mov r5, r1
  mov r6, r1
  mov r7, r1
- mov r8, r1
+ mov ip, r1
  mov lr, r1
 
  cmp r2, #96
- tstgt ip, #31
+ tstgt r0, #31
  ble 3f
 
- and r8, ip, #31
- rsb r8, r8, #32
- sub r2, r2, r8
- movs r8, r8, lsl #(32 - 4)
- stmcsia ip!, {r4, r5, r6, r7}
- stmmiia ip!, {r4, r5}
- tst r8, #(1 << 30)
- mov r8, r1
- strne r1, [ip], #4
+ and ip, r0, #31
+ rsb ip, ip, #32
+ sub r2, r2, ip
+ movs ip, ip, lsl #(32 - 4)
+ stmcsia r0!, {r4, r5, r6, r7}
+ stmmiia r0!, {r4, r5}
+ tst ip, #(1 << 30)
+ mov ip, r1
+ strne r1, [r0], #4
 
 3: subs r2, r2, #64
- stmgeia ip!, {r1, r3-r8, lr}
- stmgeia ip!, {r1, r3-r8, lr}
+ stmgeia r0!, {r1, r3-r7, ip, lr}
+ stmgeia r0!, {r1, r3-r7, ip, lr}
  bgt 3b
- ldmeqfd sp!, {r4-r8, pc}
+ ldmeqfd sp!, {r4-r7, pc}
 
  tst r2, #32
- stmneia ip!, {r1, r3-r8, lr}
+ stmneia r0!, {r1, r3-r7, ip, lr}
  tst r2, #16
- stmneia ip!, {r4-r7}
- ldmfd sp!, {r4-r8, lr}
+ stmneia r0!, {r4-r7}
+ ldmfd sp!, {r4-r7, lr}
 
 #endif
 
 4: tst r2, #8
- stmneia ip!, {r1, r3}
+ stmneia r0!, {r1, r3}
  tst r2, #4
- strne r1, [ip], #4
+ strne r1, [r0], #4
 /*
  * When we get here, we've got less than 4 bytes to zero. We
  * may have an unaligned pointer as well.
  */
 5: tst r2, #2
- strneb r1, [ip], #1
- strneb r1, [ip], #1
+ strneb r1, [r0], #1
+ strneb r1, [r0], #1
  tst r2, #1
- strneb r1, [ip], #1
+ strneb r1, [r0], #1
  mov pc, lr
 ENDPROC(memset)