2077224595858280506

2026-08-25 11:58:37 -04:00
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commit ba8692cbf2
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+---
+title: "One advantage of SAR (aka signed '>>') is that the shift-by operand HW uses only the 5|6 LSBs automatically."
+type: archive
+source: twitter
+source_url: "https://x.com/NOTimothyLottes/status/2077224595858280506"
+author: "NOTimothyLottes"
+handle: NOTimothyLottes
+post_id: "2077224595858280506"
+date: 2026-07-15
+archived: 2026-08-25
+draft: false
+tags:
+  - archive
+  - twitter
+  - NOTimothyLottes
+description: "One advantage of SAR (aka signed '>>') is that the shift-by operand HW uses only the 5|6 LSBs automatically."
+in_reply_to: ""
+---
+
+## Source
+
+- URL: https://x.com/NOTimothyLottes/status/2077224595858280506
+- Author: NOTimothyLottes (@NOTimothyLottes)
+- Posted: 2026-07-15 02:51:51
+
+## Thread
+
+**1/**
+
+One advantage of SAR (aka signed '>>') is that the shift-by operand HW uses only the 5|6 LSBs automatically. So if you have a mixed used control word, you don't have to mask out the MSBs. Can save an instruction.
+
+**2/**
+
+Working through an idea of a single uber-instruction interpreted language for code generation. Meaning something that never misses the instruction cache and executes fully out of the micro-op cache. Fully data driven with a direct map 64k entry symbol table.
+
+**3/**
+
+Borrows some ideas from SIMD GPU programming. Like instead of branching/predicating to avoid stores, just store to a discarded area (like a negative offset on the GPU, or a designated trash address on the CPU).
+
+**4/**
+
+Don't want exit condition logic in the infinite loop, so exit will have to be having the program store an exit value into a set address, and an external watchdog polling for exit at some sleep frequency.
+
+**5/**
+
+SAR on a control word can in theory grab 3 values.
+SF (sign flag) is set to MSB bit
+CF (carry flag) is set to what shifts into bit -1
+and output
+
+The SF and CF can be used for CMOVcc
+Output can be used for another shift (after CMOVccs)
@@ -1,36 +0,0 @@
---
-title: "SAR on a control word can in theory grab 3 values."
-type: archive
-source: twitter
-source_url: "https://x.com/NOTimothyLottes/status/2077241596869751029"
-author: "NOTimothyLottes"
-handle: NOTimothyLottes
-post_id: "2077241596869751029"
-date: 2026-07-15
-archived: 2026-08-23
-draft: false
-tags:
-  - archive
-  - twitter
-  - NOTimothyLottes
-description: "SAR on a control word can in theory grab 3 values."
-in_reply_to: ""
---
-
-## Source
-
- URL: https://x.com/NOTimothyLottes/status/2077241596869751029
- Author: NOTimothyLottes (@NOTimothyLottes)
- Posted: 2026-07-15 03:59:24
-
-## Thread
-
-**1/**
-
-SAR on a control word can in theory grab 3 values.
-SF (sign flag) is set to MSB bit
-CF (carry flag) is set to what shifts into bit -1
-and output
-
-The SF and CF can be used for CMOVcc
-Output can be used for another shift (after CMOVccs)
@@ -30,4 +30,5 @@ in_reply_to: ""
 Oh, F-it! The urge to drop the C baggage was too strong, using nasm to bootstrap another radical Forth for Linux. Will see how far I can get in a 4 KiB binary to start. Apparently this wants to exist, and I have no choice but to lend some fingers. ELF64 out of the way.

 ![](https://pbs.twimg.com/media/HNdzRxAXMAEom1u?format=png&name=orig)
+
 Branches: [[archive/threads/NOTimothyLottes/2026-07-17-oh-f-it-the-urge-to-drop-the-c-baggage-was-too/2026-07-18-furan-sorry-for-the-tangent-what-is-this-font-and-where]]
@@ -91,7 +91,7 @@ tags:
 - [[archive/threads/NOTimothyLottes/2026-07-13-going-all-in-to-only-if-goto-but-through-better]]
 - [[archive/threads/NOTimothyLottes/2026-07-13-ill-mark-this-down-a-more-code-obfustication-for]]
 - [[archive/threads/NOTimothyLottes/2026-07-14-another-round-of-getting-optimized-error-checking]]
- [[archive/threads/NOTimothyLottes/2026-07-15-sar-on-a-control-word-can-in-theory-grab-3-values]]
+- [[archive/threads/NOTimothyLottes/2026-07-15-one-advantage-of-sar-aka-signed-is-that-the-shift]]
 - [[archive/threads/NOTimothyLottes/2026-07-17-oh-f-it-the-urge-to-drop-the-c-baggage-was-too]]
 - [[archive/threads/NOTimothyLottes/2026-07-18-i-realized-at-some-point-i-can-have-most]]
 - [[archive/threads/NOTimothyLottes/2026-07-19-the-aim-of-course-keep-the-stuff-that-doesnt-need]]