Update JMP_TBL targets during shortcutting for x86 codegen.
Jump tables are generated from Cmm Code in a few steps:
- We start with a CmmSwitch at the end of the Cmm pipeline which gets turned into a JMP_TBL instruction.
- During native codegen we generate static jump tables from JMP_TBL. (generateJumpTables)
- We shortcut jump targets, for jump tables by updating the static tables. (shortcutBranches). This might update the jump targets with calculated address not represented by a label.
After the third step the targets in the JMP_TBL instruction (which are the original labels) and in the static data can be out of sync.
D4566 went part of the way, updating labels in JMP_TBL. However without tables next to code labels can be updated to non-label jump destinations which I did not consider at the time.
D4595 is intended to fix this.