Reduce the executable code size. #191
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… two index tables are used to access the actual entities.
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bgianfo
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@jaykrell I think you were working on this code in the recent past? Do you have any thoughts on this? |
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It is a micro optimization but yes makes sense just from the description. |
| return (this->*pEntry->pfCopy)(pEntry, pbDst + 1, pbSrc + 1); | ||
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| PBYTE CDetourDis::Copy0F78(REFCOPYENTRY, PBYTE pbDst, PBYTE pbSrc) | ||
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| // vmread, 66/extrq, F2/insertq | ||
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| static const COPYENTRY vmread = /* 78 */ ENTRY_CopyBytes2Mod; | ||
| static const COPYENTRY extrq_insertq = /* 78 */ ENTRY_CopyBytes4; | ||
| const BYTE vmread = /* 78 */ eENTRY_CopyBytes2Mod; |
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Eh, byte is maybe best and certainly works.
src/disasm.cpp
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| @@ -660,7 +654,7 @@ PBYTE CDetourDis::CopyF6(REFCOPYENTRY pEntry, PBYTE pbDst, PBYTE pbSrc) | |||
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| // TEST BYTE /0 | |||
| if (0x00 == (0x38 & pbSrc[1])) { // reg(bits 543) of ModR/M == 0 | |||
| static const COPYENTRY ce = /* f6 */ ENTRY_CopyBytes2Mod1; | |||
| const COPYENTRY ce = /* f6 */ s_rceCopyMap[eENTRY_CopyBytes2Mod1]; | |||
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reference or pointer instead of value?
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Of course, I will make another commit.
| /* 03 */ ENTRY_CopyBytes2Mod, // ADD /r | ||
| /* 04 */ ENTRY_CopyBytes2, // ADD ib | ||
| /* 05 */ ENTRY_CopyBytes3Or5, // ADD iw | ||
| /* 00 */ eENTRY_CopyBytes2Mod, // ADD /r |
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You might rephrase the PR with the same intent and even resulting bytes, but without changing these lines. i.e. just to make the diff easier to read.
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Alternatively, someone else might try to make the same change and verify they get the same result. I understand, you just prepended 'e' to every identifer, over 512 lines, it is just hard to verify.
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This is what diff -ur or git diff gave, although less straight. Please let me know how to make this more human readable.
I used a regex to generate the eENTRY_* definitions (value/name pair) from the original ones.
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I should point out. I changed all of this code so the main handler function is templatized, and the table is filled with (mostly?) instantiated pointers to it. So that ends up around 512*8=2k and perhaps faster, perhaps a little larger. |
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Any updates on this? |
- Deduplicate code - Reduce constant table size (see also microsoft#191 by jdp1024)
- Deduplicate code and fix formatting - Reduce constant table size (see also microsoft#191 by jdp1024)
In the original version of Detours, s_rceCopyTable and s_rceCopyTable0F are two big arrays, both consisting of 256 COPYENTRY's, occupying 256*(8+8)*2=8192 bytes. To reduce the executable code size, those two arrays are changed to use the index to a COPYENTRY array instead of the actual entity.
s_rceCopyTable and s_rceCopyTable0F now are arrays of 256 BYTEs, the COPYENTRY array consists of only the 45 unique operands. All these occupy 2562+45(8+8)=1232 bytes, thus we save 7060 bytes with almost no performance sacrifice.
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