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.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.5 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler (NCG) |
| Test case | |
| Differential revisions | |
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| Related | |
| Blocking | |
| CC | |
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