On ARM, the gd pointer is stored in registers r9 / x18. For this the -ffixed-r9 / -ffixed-x18 flag is used when compiling, but using global register variables causes errors when building with LTO, and these errors are very difficult to overcome.
Richard Biener says [1]: Note that global register vars shouldn't be used with LTO and if they are restricted to just a few compilation units the recommended fix is to build those CUs without -flto.
We cannot do this for U-Boot since all CUs use -ffixed-reg flag.
It seems that with LTO we could in fact store the gd pointer differently and gain performance or size benefit by allowing the compiler to use r9 / x18. But this would need more work.
So for now, when building with LTO, go the clang way, and instead of declaring gd a global register variable, we make it a function call via macro.
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68384
Signed-off-by: Marek Behún marek.behun@nic.cz --- arch/arm/cpu/arm926ejs/mxs/spl_boot.c | 2 +- arch/arm/include/asm/global_data.h | 2 +- arch/arm/mach-exynos/spl_boot.c | 2 +- arch/arm/mach-imx/imx8m/soc.c | 2 +- arch/arm/mach-imx/spl_imx_romapi.c | 16 ++++++++-------- 5 files changed, 12 insertions(+), 12 deletions(-)
diff --git a/arch/arm/cpu/arm926ejs/mxs/spl_boot.c b/arch/arm/cpu/arm926ejs/mxs/spl_boot.c index a16a15e79d..66406cc857 100644 --- a/arch/arm/cpu/arm926ejs/mxs/spl_boot.c +++ b/arch/arm/cpu/arm926ejs/mxs/spl_boot.c @@ -122,7 +122,7 @@ void mxs_common_spl_init(const uint32_t arg, const uint32_t *resptr, { struct mxs_spl_data *data = MXS_SPL_DATA; uint8_t bootmode = mxs_get_bootmode_index(); - gd = &gdata; + set_gd(&gdata);
mxs_spl_fixup_vectors();
diff --git a/arch/arm/include/asm/global_data.h b/arch/arm/include/asm/global_data.h index bb82efafa6..2aff1c467c 100644 --- a/arch/arm/include/asm/global_data.h +++ b/arch/arm/include/asm/global_data.h @@ -91,7 +91,7 @@ struct arch_global_data {
#include <asm-generic/global_data.h>
-#ifdef __clang__ +#if defined(__clang__) || defined(CONFIG_LTO)
#define DECLARE_GLOBAL_DATA_PTR #define gd get_gd() diff --git a/arch/arm/mach-exynos/spl_boot.c b/arch/arm/mach-exynos/spl_boot.c index 27f0dac182..722449881a 100644 --- a/arch/arm/mach-exynos/spl_boot.c +++ b/arch/arm/mach-exynos/spl_boot.c @@ -279,7 +279,7 @@ void memzero(void *s, size_t n) */ static void setup_global_data(gd_t *gdp) { - gd = gdp; + set_gd(gdp); memzero((void *)gd, sizeof(gd_t)); gd->flags |= GD_FLG_RELOC; gd->baudrate = CONFIG_BAUDRATE; diff --git a/arch/arm/mach-imx/imx8m/soc.c b/arch/arm/mach-imx/imx8m/soc.c index 5f37282ff1..15d0da7060 100644 --- a/arch/arm/mach-imx/imx8m/soc.c +++ b/arch/arm/mach-imx/imx8m/soc.c @@ -509,7 +509,7 @@ enum boot_device get_boot_device(void)
ret = g_rom_api->query_boot_infor(QUERY_BT_DEV, &boot, ((uintptr_t)&boot) ^ QUERY_BT_DEV); - gd = pgd; + set_gd(pgd);
if (ret != ROM_API_OKAY) { puts("ROMAPI: failure at query_boot_info\n"); diff --git a/arch/arm/mach-imx/spl_imx_romapi.c b/arch/arm/mach-imx/spl_imx_romapi.c index 9f4d95982e..d2085dabd3 100644 --- a/arch/arm/mach-imx/spl_imx_romapi.c +++ b/arch/arm/mach-imx/spl_imx_romapi.c @@ -45,7 +45,7 @@ static ulong spl_romapi_read_seekable(struct spl_load_info *load,
ret = g_rom_api->download_image(buf, offset, byte, ((uintptr_t)buf) ^ offset ^ byte); - gd = pgd; + set_gd(pgd);
if (ret == ROM_API_OKAY) return count; @@ -73,7 +73,7 @@ static int spl_romapi_load_image_seekable(struct spl_image_info *spl_image, ret |= g_rom_api->query_boot_infor(QUERY_IMG_OFF, &image_offset, ((uintptr_t)&image_offset) ^ QUERY_IMG_OFF);
- gd = pgd; + set_gd(pgd);
if (ret != ROM_API_OKAY) { puts("ROMAPI: Failure query boot infor pagesize/offset\n"); @@ -94,7 +94,7 @@ static int spl_romapi_load_image_seekable(struct spl_image_info *spl_image, size = ALIGN(sizeof(struct image_header), pagesize); ret = g_rom_api->download_image((u8 *)header, offset, size, ((uintptr_t)header) ^ offset ^ size); - gd = pgd; + set_gd(pgd);
if (ret != ROM_API_OKAY) { printf("ROMAPI: download failure offset 0x%x size 0x%x\n", @@ -180,7 +180,7 @@ static int spl_romapi_load_image_stream(struct spl_image_info *spl_image,
ret = g_rom_api->query_boot_infor(QUERY_PAGE_SZ, &pagesize, ((uintptr_t)&pagesize) ^ QUERY_PAGE_SZ); - gd = pgd; + set_gd(pgd);
if (ret != ROM_API_OKAY) puts("failure at query_boot_info\n"); @@ -192,7 +192,7 @@ static int spl_romapi_load_image_stream(struct spl_image_info *spl_image, for (i = 0; i < 640; i++) { ret = g_rom_api->download_image(p, 0, pg, ((uintptr_t)p) ^ pg); - gd = pgd; + set_gd(pgd);
if (ret != ROM_API_OKAY) { puts("Steam(USB) download failure\n"); @@ -213,7 +213,7 @@ static int spl_romapi_load_image_stream(struct spl_image_info *spl_image,
if (p - pfit < sizeof(struct fdt_header)) { ret = g_rom_api->download_image(p, 0, pg, ((uintptr_t)p) ^ pg); - gd = pgd; + set_gd(pgd);
if (ret != ROM_API_OKAY) { puts("Steam(USB) download failure\n"); @@ -237,7 +237,7 @@ static int spl_romapi_load_image_stream(struct spl_image_info *spl_image,
ret = g_rom_api->download_image(p, 0, imagesize, ((uintptr_t)p) ^ imagesize); - gd = pgd; + set_gd(pgd);
p += imagesize;
@@ -280,7 +280,7 @@ int board_return_to_bootrom(struct spl_image_info *spl_image,
ret = g_rom_api->query_boot_infor(QUERY_BT_DEV, &boot, ((uintptr_t)&boot) ^ QUERY_BT_DEV); - gd = pgd; + set_gd(pgd);
if (ret != ROM_API_OKAY) { puts("ROMAPI: failure at query_boot_info\n");