Commit 0df01fd3d71481b5cc7aeea6a741b9fc3be15178
Committed by
Scott McNutt
Scott McNutt
1 parent
661ba14051
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master
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54 other branches
nios2: fix r15 issue for gcc4
The "-ffixed-r15" option doesn't work well for gcc4. Since we don't use gp for small data with option "-G0", we can use gp as global data pointer. This allows compiler to use r15. It is necessary for gcc4 to work properly. Signed-off-by: Thomas Chou <thomas@wytron.com.tw> Signed-off-by: Scott McNutt <smcnutt@psyent.com>
Showing 6 changed files with 20 additions and 18 deletions Side-by-side Diff
README
| ... | ... | @@ -4023,6 +4023,14 @@ |
| 4023 | 4023 | |
| 4024 | 4024 | ==> U-Boot will use R8 to hold a pointer to the global data |
| 4025 | 4025 | |
| 4026 | +On Nios II, the ABI is documented here: | |
| 4027 | + http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf | |
| 4028 | + | |
| 4029 | + ==> U-Boot will use gp to hold a pointer to the global data | |
| 4030 | + | |
| 4031 | + Note: on Nios II, we give "-G0" option to gcc and don't use gp | |
| 4032 | + to access small data sections, so gp is free. | |
| 4033 | + | |
| 4026 | 4034 | NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope, |
| 4027 | 4035 | or current versions of GCC may "optimize" the code too much. |
| 4028 | 4036 |
arch/nios2/config.mk
arch/nios2/cpu/start.S
| ... | ... | @@ -113,13 +113,6 @@ |
| 113 | 113 | bne r5, r6, 4b |
| 114 | 114 | 5: |
| 115 | 115 | |
| 116 | - /* GLOBAL POINTER -- the global pointer is used to reference | |
| 117 | - * "small data" (see -G switch). The linker script must | |
| 118 | - * provide the gp address. | |
| 119 | - */ | |
| 120 | - movhi gp, %hi(_gp) | |
| 121 | - ori gp, gp, %lo(_gp) | |
| 122 | - | |
| 123 | 116 | /* JUMP TO RELOC ADDR */ |
| 124 | 117 | movhi r4, %hi(_reloc) |
| 125 | 118 | ori r4, r4, %lo(_reloc) |
arch/nios2/include/asm/global_data.h
| ... | ... | @@ -48,7 +48,7 @@ |
| 48 | 48 | #define GD_FLG_LOGINIT 0x00020 /* Log Buffer has been initialized */ |
| 49 | 49 | #define GD_FLG_DISABLE_CONSOLE 0x00040 /* Disable console (in & out) */ |
| 50 | 50 | |
| 51 | -#define DECLARE_GLOBAL_DATA_PTR register gd_t *gd asm ("r15") | |
| 51 | +#define DECLARE_GLOBAL_DATA_PTR register gd_t *gd asm ("gp") | |
| 52 | 52 | |
| 53 | 53 | #endif /* __ASM_NIOS2_GLOBALDATA_H_ */ |
doc/README.standalone
| ... | ... | @@ -19,12 +19,12 @@ |
| 19 | 19 | thus the compiler cannot perform type checks on these assignments. |
| 20 | 20 | |
| 21 | 21 | 2. The pointer to the jump table is passed to the application in a |
| 22 | - machine-dependent way. PowerPC, ARM, MIPS and Blackfin architectures | |
| 23 | - use a dedicated register to hold the pointer to the 'global_data' | |
| 24 | - structure: r2 on PowerPC, r8 on ARM, k0 on MIPS, and P3 on Blackfin. | |
| 25 | - The x86 architecture does not use such a register; instead, the | |
| 26 | - pointer to the 'global_data' structure is passed as 'argv[-1]' | |
| 27 | - pointer. | |
| 22 | + machine-dependent way. PowerPC, ARM, MIPS, Blackfin and Nios II | |
| 23 | + architectures use a dedicated register to hold the pointer to the | |
| 24 | + 'global_data' structure: r2 on PowerPC, r8 on ARM, k0 on MIPS, | |
| 25 | + P3 on Blackfin and gp on Nios II. The x86 architecture does not | |
| 26 | + use such a register; instead, the pointer to the 'global_data' | |
| 27 | + structure is passed as 'argv[-1]' pointer. | |
| 28 | 28 | |
| 29 | 29 | The application can access the 'global_data' structure in the same |
| 30 | 30 | way as U-Boot does: |
| ... | ... | @@ -56,6 +56,7 @@ |
| 56 | 56 | ARM 0x0c100000 0x0c100000 |
| 57 | 57 | MIPS 0x80200000 0x80200000 |
| 58 | 58 | Blackfin 0x00001000 0x00001000 |
| 59 | + Nios II 0x02000000 0x02000000 | |
| 59 | 60 | |
| 60 | 61 | For example, the "hello world" application may be loaded and |
| 61 | 62 | executed on a PowerPC board with the following commands: |
examples/standalone/stubs.c
| ... | ... | @@ -84,7 +84,7 @@ |
| 84 | 84 | : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x) : "r0"); |
| 85 | 85 | #elif defined(CONFIG_NIOS2) |
| 86 | 86 | /* |
| 87 | - * r15 holds the pointer to the global_data, r8 is call-clobbered | |
| 87 | + * gp holds the pointer to the global_data, r8 is call-clobbered | |
| 88 | 88 | */ |
| 89 | 89 | #define EXPORT_FUNC(x) \ |
| 90 | 90 | asm volatile ( \ |
| 91 | 91 | |
| ... | ... | @@ -92,11 +92,11 @@ |
| 92 | 92 | #x ":\n" \ |
| 93 | 93 | " movhi r8, %%hi(%0)\n" \ |
| 94 | 94 | " ori r8, r0, %%lo(%0)\n" \ |
| 95 | -" add r8, r8, r15\n" \ | |
| 95 | +" add r8, r8, gp\n" \ | |
| 96 | 96 | " ldw r8, 0(r8)\n" \ |
| 97 | 97 | " ldw r8, %1(r8)\n" \ |
| 98 | 98 | " jmp r8\n" \ |
| 99 | - : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "r15"); | |
| 99 | + : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "gp"); | |
| 100 | 100 | #elif defined(CONFIG_M68K) |
| 101 | 101 | /* |
| 102 | 102 | * d7 holds the pointer to the global_data, a0 is a call-clobbered |