diff options
Diffstat (limited to 'docs/HistoricalNotes/2000-12-06-EncodingIdea.txt')
| -rw-r--r-- | docs/HistoricalNotes/2000-12-06-EncodingIdea.txt | 30 |
1 files changed, 0 insertions, 30 deletions
diff --git a/docs/HistoricalNotes/2000-12-06-EncodingIdea.txt b/docs/HistoricalNotes/2000-12-06-EncodingIdea.txt deleted file mode 100644 index 8c45292..0000000 --- a/docs/HistoricalNotes/2000-12-06-EncodingIdea.txt +++ /dev/null @@ -1,30 +0,0 @@ -From: Chris Lattner [mailto:sabre@nondot.org] -Sent: Wednesday, December 06, 2000 6:41 PM -To: Vikram S. Adve -Subject: Additional idea with respect to encoding - -Here's another idea with respect to keeping the common case instruction -size down (less than 32 bits ideally): - -Instead of encoding an instruction to operate on two register numbers, -have it operate on two negative offsets based on the current register -number. Therefore, instead of using: - -r57 = add r55, r56 (r57 is the implicit dest register, of course) - -We could use: - -r57 = add -2, -1 - -My guess is that most SSA references are to recent values (especially if -they correspond to expressions like (x+y*z+p*q/ ...), so the negative -numbers would tend to stay small, even at the end of the procedure (where -the implicit register destination number could be quite large). Of course -the negative sign is reduntant, so you would be storing small integers -almost all of the time, and 5-6 bits worth of register number would be -plenty for most cases... - -What do you think? - --Chris - |