On Tue, 2015-09-22 at 22:57 +0200, Christophe Leroy wrote: > Here is what I get in asm. First one is with "if (i) mb();". We see gcc > puts a beqlr. This is the form that is closest to what we had in the > former misc_32.S > Second one if with "mb()". Here we get a branch to sync for a useless sync
I was more concerned with keeping the code simple than the asm output. > c000e0ac <my_flush_dcache_range1>: > c000e0ac: 54 63 00 36 rlwinm r3,r3,0,0,27 > c000e0b0: 38 84 00 0f addi r4,r4,15 > c000e0b4: 7d 23 20 50 subf r9,r3,r4 > c000e0b8: 55 29 e1 3f rlwinm. r9,r9,28,4,31 > c000e0bc: 4d 82 00 20 beqlr > c000e0c0: 7d 29 03 a6 mtctr r9 > c000e0c4: 7c 00 18 6c dcbst 0,r3 > c000e0c8: 38 63 00 10 addi r3,r3,16 > c000e0cc: 42 00 ff f8 bdnz c000e0c4 > <my_flush_dcache_range1+0x18> > c000e0d0: 7c 00 04 ac sync > c000e0d4: 4e 80 00 20 blr > > c000e0d8 <my_flush_dcache_range2>: > c000e0d8: 54 63 00 36 rlwinm r3,r3,0,0,27 > c000e0dc: 38 84 00 0f addi r4,r4,15 > c000e0e0: 7d 23 20 50 subf r9,r3,r4 > c000e0e4: 55 29 e1 3f rlwinm. r9,r9,28,4,31 > c000e0e8: 41 82 00 14 beq c000e0fc > <my_flush_dcache_range2+0x24> > c000e0ec: 7d 29 03 a6 mtctr r9 > c000e0f0: 7c 00 18 6c dcbst 0,r3 > c000e0f4: 38 63 00 10 addi r3,r3,16 > c000e0f8: 42 00 ff f8 bdnz c000e0f0 > <my_flush_dcache_range2+0x18> > c000e0fc: 7c 00 04 ac sync > c000e100: 4e 80 00 20 blr Who cares whether the case that should rarely if ever happen gets a beqlr or a branch to sync+blr? -Scott -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
