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fix: preserve SSE state in x86_64 bthread context switch #21

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fix: preserve SSE state in x86_64 bthread context switch #21

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28cf5de
fix: preserve SSE state in x86_64 bthread context switch
Aug 21, 2026
3a44640
fix: initialize control words at updated context offsets
Aug 22, 2026
dd16341
fix: update task tracer for expanded context frame
Aug 22, 2026
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42 changes: 31 additions & 11 deletions src/bthread/context.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -347,20 +347,40 @@ __asm (
" pushq %r14 \n"
" pushq %r13 \n"
" pushq %r12 \n"
" leaq -0x8(%rsp), %rsp\n"
" leaq -0xa8(%rsp), %rsp\n"
" movups %xmm6, 0x00(%rsp)\n"
" movups %xmm7, 0x10(%rsp)\n"
" movups %xmm8, 0x20(%rsp)\n"
" movups %xmm9, 0x30(%rsp)\n"
" movups %xmm10, 0x40(%rsp)\n"
" movups %xmm11, 0x50(%rsp)\n"
" movups %xmm12, 0x60(%rsp)\n"
" movups %xmm13, 0x70(%rsp)\n"
" movups %xmm14, 0x80(%rsp)\n"
" movups %xmm15, 0x90(%rsp)\n"
" cmp $0, %rcx\n"
" je 1f\n"
" stmxcsr (%rsp)\n"
" fnstcw 0x4(%rsp)\n"
" stmxcsr 0xa0(%rsp)\n"
" fnstcw 0xa4(%rsp)\n"
"1:\n"
" movq %rsp, (%rdi)\n"
" movq %rsi, %rsp\n"
" movups 0x00(%rsp), %xmm6\n"
" movups 0x10(%rsp), %xmm7\n"
" movups 0x20(%rsp), %xmm8\n"
" movups 0x30(%rsp), %xmm9\n"
" movups 0x40(%rsp), %xmm10\n"
" movups 0x50(%rsp), %xmm11\n"
" movups 0x60(%rsp), %xmm12\n"
" movups 0x70(%rsp), %xmm13\n"
" movups 0x80(%rsp), %xmm14\n"
" movups 0x90(%rsp), %xmm15\n"
" cmp $0, %rcx\n"
" je 2f\n"
" ldmxcsr (%rsp)\n"
" fldcw 0x4(%rsp)\n"
" ldmxcsr 0xa0(%rsp)\n"
" fldcw 0xa4(%rsp)\n"
"2:\n"
" leaq 0x8(%rsp), %rsp\n"
" leaq 0xa8(%rsp), %rsp\n"
" popq %r12 \n"
" popq %r13 \n"
" popq %r14 \n"
Expand All @@ -387,12 +407,12 @@ __asm (
"bthread_make_fcontext:\n"
" movq %rdi, %rax\n"
" andq $-16, %rax\n"
" leaq -0x48(%rax), %rax\n"
" movq %rdx, 0x38(%rax)\n"
" stmxcsr (%rax)\n"
" fnstcw 0x4(%rax)\n"
" leaq -0xe8(%rax), %rax\n"
" movq %rdx, 0xd8(%rax)\n"
" stmxcsr 0xa0(%rax)\n"
" fnstcw 0xa4(%rax)\n"
" leaq finish(%rip), %rcx\n"
" movq %rcx, 0x40(%rax)\n"
" movq %rcx, 0xe0(%rax)\n"
" ret \n"
"finish:\n"
" xorq %rdi, %rdi\n"
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6 changes: 3 additions & 3 deletions src/bthread/task_tracer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -280,16 +280,16 @@ unw_cursor_t TaskTracer::MakeCursor(bthread_fcontext_t fcontext) {

// Only need RBP, RIP, RSP on x86_64.
// The base pointer (RBP).
if (unw_set_reg(&cursor, UNW_X86_64_RBP, regs[6]) != 0) {
if (unw_set_reg(&cursor, UNW_X86_64_RBP, regs[26]) != 0) {
LOG(ERROR) << "Fail to set RBP";
}
// The instruction pointer (RIP).
if (unw_set_reg(&cursor, UNW_REG_IP, regs[7]) != 0) {
if (unw_set_reg(&cursor, UNW_REG_IP, regs[27]) != 0) {
LOG(ERROR) << "Fail to set RIP";
}
#if UNW_VERSION_MAJOR >= 1 && UNW_VERSION_MINOR >= 7
// The stack pointer (RSP).
if (unw_set_reg(&cursor, UNW_REG_SP, regs[8]) != 0) {
if (unw_set_reg(&cursor, UNW_REG_SP, regs[28]) != 0) {
LOG(ERROR) << "Fail to set RSP";
}
#endif
Expand Down