linux/kernel/dma
Petr Tesarik d069ed288a swiotlb: optimize get_max_slots()
Use a simple logical shift and increment to calculate the number of slots
taken by the DMA segment boundary.

At least GCC-13 is not able to optimize the expression, producing this
horrible assembly code on x86:

	cmpq	$-1, %rcx
	je	.L364
	addq	$2048, %rcx
	shrq	$11, %rcx
	movq	%rcx, %r13
.L331:
	// rest of the function here...

	// after function epilogue and return:
.L364:
	movabsq $9007199254740992, %r13
	jmp	.L331

After the optimization, the code looks more reasonable:

	shrq	$11, %r11
	leaq	1(%r11), %rbx

Signed-off-by: Petr Tesarik <petr.tesarik.ext@huawei.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
2023-08-08 10:29:21 -07:00
..
coherent.c dma-mapping: Add dma_release_coherent_memory to DMA API 2022-06-24 09:30:54 -06:00
contiguous.c dma-contiguous: check for memory region overlap 2023-07-31 17:54:56 +02:00
debug.c dma-debug: Use %pa to format phys_addr_t 2023-03-30 08:51:52 +09:00
debug.h dma-debug: teach add_dma_entry() about DMA_ATTR_SKIP_CPU_SYNC 2021-10-18 12:46:45 +02:00
direct.c swiotlb: if swiotlb is full, fall back to a transient memory pool 2023-08-01 18:02:20 +02:00
direct.h dma-mapping: force bouncing if the kmalloc() size is not cache-line-aligned 2023-06-19 16:19:23 -07:00
dummy.c dma-mapping: return error code from dma_dummy_map_sg() 2021-08-09 17:13:06 +02:00
Kconfig swiotlb: add a flag whether SWIOTLB is allowed to grow 2023-08-01 18:02:17 +02:00
Makefile dma-mapping: remove CONFIG_DMA_REMAP 2022-03-03 14:00:57 +03:00
map_benchmark.c dma-mapping: benchmark: remove MODULE_LICENSE in non-modules 2023-04-13 13:13:51 -07:00
mapping.c dma-mapping: move arch_dma_set_mask() declaration to header 2023-07-31 17:54:28 +02:00
ops_helpers.c dma-mapping: handle vmalloc addresses in dma_common_{mmap,get_sgtable} 2021-07-16 11:30:26 +02:00
pool.c mm, treewide: redefine MAX_ORDER sanely 2023-04-05 19:42:46 -07:00
remap.c dma-remap: use kvmalloc_array/kvfree for larger dma memory remap 2023-06-07 15:06:28 +02:00
swiotlb.c swiotlb: optimize get_max_slots() 2023-08-08 10:29:21 -07:00