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Diffstat (limited to 'chapter24/README.md')
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1 files changed, 13 insertions, 7 deletions
diff --git a/chapter24/README.md b/chapter24/README.md index a1fb6ded..58e13f39 100644 --- a/chapter24/README.md +++ b/chapter24/README.md @@ -296,19 +296,25 @@ also covers a backedge-only conflict where the first attempt inserts no copy: that attempt must still consume the one permitted delay. A regression checks both the cheaper first attempt and the mandatory fallback. +Chapter 21's adjacent-copy forwarding also carries forward: after coloring, +a sole use in the next instruction can read the source register when its +operand mask permits it and no two-address tie is broken. The table below +includes this cleanup. Cohort 22 now also includes the two zero-move C return +ABI checks added since the earlier audit (26 entries instead of 24). + Run `make spill-stats`. All rows use **Chapter 24's compiler**, optimizer seed 123, and the same source/target combinations as the earlier cohort tables. These Windows results combine x86 SystemV/Win64 and RISC-V/ARM SystemV, remeasured on 2026-09-28 after the function-pointer lifetime backport. -| Program cohort | Compilations | Split/move count | Loop-weighted count | +| Program cohort | Compilations | Retained moves | Loop-weighted moves | |---|---:|---:|---:| -| Chapter 20 | 39 | 323 | 442 | -| Chapter 21 | 52 | 436 | 975 | -| Chapter 22 | 24 | 67 | 67 | -| Chapter 23 | 30 | 84 | 231 | -| Chapter 24 | 67 | 441 | 1,400 | -| **Total** | **212** | **1,351** | **3,115** | +| Chapter 20 | 39 | 319 | 431 | +| Chapter 21 | 52 | 425 | 957 | +| Chapter 22 | 26 | 67 | 67 | +| Chapter 23 | 30 | 81 | 228 | +| Chapter 24 | 67 | 418 | 1,286 | +| **Total** | **214** | **1,310** | **2,969** | `_spills` counts retained SplitNodes, including register moves. `_spillScaled` weights those moves by `8^loopDepth`; it is a cost estimate, not measured memory |