[lldb][swift] Increase number of Rows inspected when unwinding async functions #10698
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jasonmolenda
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May 17, 2025
…functions We were overly conservatives in our initial estimations: if callee saved registers are used, they are usually spilled first, increasing the number of rows in the prologue. This also revealed an embarrassing bug in how we computed the offset of a iterator in the vector: ``` - int row_idx = fp_locs.end() - it; + int row_idx = it - fp_locs.begin(); ```
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I spoke in DM with Felipe about one small concern, the AAPCS ABI has 10 general purpose registers marked callee-preserved, and 8 floating point registers. If they're stored with STP instructions, that means we can have the initial unwind state row, two standard prologue rows, and then 9 rows of registers being stored to stack before the stack pointer is copied into the frame pointer, worst possible case? |
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We were overly conservatives in our initial estimations: if callee saved registers are used, they are usually spilled first, increasing the number of rows in the prologue.