Copy propagation tweaking #64378
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Copy propagation tweaking #64378
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Tagging subscribers to this area: @JulieLeeMSFT Issue DetailsSome small CQ improvements in preparation for a zero-diff TP-oriented refactoring.
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@dotnet/jit-contrib |
The type check is too conservative: it prevents partial
definitions from being used in propagation:
```
LCL_FLD V00/1 [X] = { ... }; // Pushed on the stack as a def.
USE LCL_VAR V01 // Has the same VN as V00/1, but the type
// check prevented it from being replaced.
```
This new version is conservative too, but will do for now
as we don't propagate on (most) partial uses.
Another reason for this change is that in my upcoming refactoring
of copy propagation (that will bring another 0.5% in TP gains), we
will no longer have the "defNode" available.
Ordinarily, shadowed parameters would not be used for propagation anyway, because of the liveness check, but "this" bypasses that checks, and so was used, which is presumably not what we want. Regardless of that, it is also not profitable to propagate "this" in such a situation as it extends its live range and makes the RA unhappy.
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AndyAyersMS
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Feb 9, 2022
src/coreclr/jit/compiler.h
Outdated
| @@ -10858,6 +10858,8 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX | |||
| public: | |||
| struct ShadowParamVarInfo | |||
| { | |||
| static const unsigned NO_SHADOW_COPY = UINT_MAX; | |||
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Nit: why not just use BAD_VAR_NUM?
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I suppose no reason. Deleted it.
AndyAyersMS
approved these changes
Feb 10, 2022
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Some small CQ improvements in preparation for a zero-diff TP-oriented refactoring.
Please refer to the individual commit messages for details.
Diffs.