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[libcpu][cortex-a] Refactor FPU stack initialization for maintainability #10919

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Merged
BernardXiong merged 3 commits into from
Nov 11, 2025
Merged

[libcpu][cortex-a] Refactor FPU stack initialization for maintainability #10919

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Copilot Nov 11, 2025
4dc072c
[libcpu][cortex-a] Improve FPU stack initialization implementation
Copilot Nov 11, 2025
06eae47
[libcpu][cortex-a] Replace FPU init loop with rt_memset
Copilot Nov 11, 2025
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5 changes: 5 additions & 0 deletions libcpu/arm/cortex-a/cpuport.h
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Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,11 @@ struct rt_hw_stack
#define E_Bit (1<<9)
#define J_Bit (1<<24)

/* VFP/NEON register count for FPU context */
#ifndef VFP_DATA_NR
#define VFP_DATA_NR 64 /* 32 double-precision registers = 64 words */
#endif

#ifdef RT_USING_SMP
typedef union {
unsigned long slock;
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8 changes: 7 additions & 1 deletion libcpu/arm/cortex-a/stack.c
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Expand Up @@ -61,7 +61,13 @@ rt_uint8_t *rt_hw_stack_init(void *tentry, void *parameter,
*(--stk) = 0; /* user sp*/
#endif
#ifdef RT_USING_FPU
*(--stk) = 0; /* not use fpu*/
/* FPU context initialization matches context_gcc.S restore order:
* Stack layout (high to low): FPEXC -> FPSCR -> D16-D31 -> D0-D15
*/
stk -= VFP_DATA_NR;
rt_memset(stk, 0, VFP_DATA_NR * sizeof(rt_uint32_t)); /* Initialize D0-D31 (64 words for 32 double regs) */
*(--stk) = 0; /* FPSCR: Floating-Point Status and Control Register */
*(--stk) = 0x40000000; /* FPEXC: Enable FPU (bit 30 = EN) */
#endif

/* return task's current stack address */
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