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[Andreas Cadhalpun <Andreas.Cadhalpun@xxxxxxxxx>]

Debugging the failing command 'libavcodec/dct-test -i' with gdb shows
that this is clearly a binutils bug.

* Working with binutils 2.25.1-6ubuntu1:
Breakpoint 1, __end_a_evaluation () at libavcodec/arm/simple_idct_arm.S:239
239	        ldr r10, =MASK_MSHW      @ R10=0xFFFF0000
(gdb) disas
Dump of assembler code for function __end_a_evaluation:
   0x00012c08 <+0>:	add.w	r8, r6, r0
   0x00012c0c <+4>:	add.w	r9, r2, r1
=> 0x00012c10 <+8>:	ldr.w	r10, [pc, #540]	; 0x12e30 <__end_bef_a_evaluation+44>
   0x00012c14 <+12>:	and.w	r9, r10, r9, lsl #5
   0x00012c18 <+16>:	mvn.w	r11, r10
   0x00012c1c <+20>:	and.w	r8, r11, r8, asr #11
   0x00012c20 <+24>:	orr.w	r8, r8, r9
   0x00012c24 <+28>:	str.w	r8, [lr]
   0x00012c28 <+32>:	add.w	r8, r3, r5
   0x00012c2c <+36>:	add.w	r9, r4, r7
   0x00012c30 <+40>:	and.w	r9, r10, r9, lsl #5
   0x00012c34 <+44>:	and.w	r8, r11, r8, asr #11
   0x00012c38 <+48>:	orr.w	r8, r8, r9
   0x00012c3c <+52>:	str.w	r8, [lr, #4]
   0x00012c40 <+56>:	sub.w	r8, r4, r7
   0x00012c44 <+60>:	sub.w	r9, r3, r5
   0x00012c48 <+64>:	and.w	r9, r10, r9, lsl #5
   0x00012c4c <+68>:	and.w	r8, r11, r8, asr #11
   0x00012c50 <+72>:	orr.w	r8, r8, r9
   0x00012c54 <+76>:	str.w	r8, [lr, #8]
   0x00012c58 <+80>:	sub.w	r8, r2, r1
   0x00012c5c <+84>:	sub.w	r9, r6, r0
   0x00012c60 <+88>:	and.w	r9, r10, r9, lsl #5
   0x00012c64 <+92>:	and.w	r8, r11, r8, asr #11
   0x00012c68 <+96>:	orr.w	r8, r8, r9
   0x00012c6c <+100>:	str.w	r8, [lr, #12]
   0x00012c70 <+104>:	b.n	0x12c92 <__end_row_loop>
End of assembler dump.
(gdb) info registers r10
r10            0x22a3	8867
(gdb) n
240	        and r9, r10, r9, lsl #ROW_SHIFT2MSHW @ R9=0xFFFF0000 & ((a1+b1)<<5)
(gdb) info registers r10
r10            0xffff0000	-65536

This correctly sets the r10 register to 0xFFFF0000.

 * Broken with bintuils 2.25.51.20151028-0ubuntu1:
Breakpoint 1, __end_a_evaluation () at libavcodec/arm/simple_idct_arm.S:239
239	        ldr r10, =MASK_MSHW      @ R10=0xFFFF0000
(gdb) disas
Dump of assembler code for function __end_a_evaluation:
   0x00012c08 <+0>:	add.w	r8, r6, r0
   0x00012c0c <+4>:	add.w	r9, r2, r1
=> 0x00012c10 <+8>:	movt	r10, #65535	; 0xffff
   0x00012c14 <+12>:	and.w	r9, r10, r9, lsl #5
   0x00012c18 <+16>:	mvn.w	r11, r10
   0x00012c1c <+20>:	and.w	r8, r11, r8, asr #11
   0x00012c20 <+24>:	orr.w	r8, r8, r9
   0x00012c24 <+28>:	str.w	r8, [lr]
   0x00012c28 <+32>:	add.w	r8, r3, r5
   0x00012c2c <+36>:	add.w	r9, r4, r7
   0x00012c30 <+40>:	and.w	r9, r10, r9, lsl #5
   0x00012c34 <+44>:	and.w	r8, r11, r8, asr #11
   0x00012c38 <+48>:	orr.w	r8, r8, r9
   0x00012c3c <+52>:	str.w	r8, [lr, #4]
   0x00012c40 <+56>:	sub.w	r8, r4, r7
   0x00012c44 <+60>:	sub.w	r9, r3, r5
   0x00012c48 <+64>:	and.w	r9, r10, r9, lsl #5
   0x00012c4c <+68>:	and.w	r8, r11, r8, asr #11
   0x00012c50 <+72>:	orr.w	r8, r8, r9
   0x00012c54 <+76>:	str.w	r8, [lr, #8]
   0x00012c58 <+80>:	sub.w	r8, r2, r1
   0x00012c5c <+84>:	sub.w	r9, r6, r0
   0x00012c60 <+88>:	and.w	r9, r10, r9, lsl #5
   0x00012c64 <+92>:	and.w	r8, r11, r8, asr #11
   0x00012c68 <+96>:	orr.w	r8, r8, r9
   0x00012c6c <+100>:	str.w	r8, [lr, #12]
   0x00012c70 <+104>:	b.n	0x12c92 <__end_row_loop>
End of assembler dump.
(gdb) info registers r10
r10            0x22a3	8867
(gdb) n
240	        and r9, r10, r9, lsl #ROW_SHIFT2MSHW @ R9=0xFFFF0000 & ((a1+b1)<<5)
(gdb) info registers r10
r10            0xffff22a3	-56669

This only sets the upper half of r10, leaving the lower half untouched.

** Changed in: binutils (Ubuntu)
       Status: New => Confirmed

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https://bugs.launchpad.net/bugs/1513985

Title:
  ffmpeg test idct8x8 (NEON) fails on ARM32 when built with binutils
  from the trunk

Status in binutils:
  Unknown
Status in binutils package in Ubuntu:
  Confirmed
Status in ffmpeg package in Ubuntu:
  New

Bug description:
  ffmpeg test idct8x8 (NEON) fails on ARM32 when built with binutils
  from the trunk

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