explicitly mention subnormal flushing

[web.git] / personal / _posts / 2026-03-13-inline-asm.md

diff --git a/personal/_posts/2026-03-13-inline-asm.md b/personal/_posts/2026-03-13-inline-asm.md
index 87a5fbf68fd5e726cfc1798ce3249152807e3941..f577a1d68decbcb92d9081ba1214a1816e756cac 100644 (file)
--- a/personal/_posts/2026-03-13-inline-asm.md
+++ b/personal/_posts/2026-03-13-inline-asm.md
@@ -263,7 +263,7 @@ The Abstract Machine has no floating-point status bits that the story code could
 This directly reflects the fact that the compiler makes no guarantees for the value that the program will observe in the status register, and since floating-point operations can be arbitrarily reordered, this should be taken quite literally.
 
 For writing the control register, there simply is no possible story: no Rust operation exists that would change the rounding mode of subsequent floating-point operations.
 This directly reflects the fact that the compiler makes no guarantees for the value that the program will observe in the status register, and since floating-point operations can be arbitrarily reordered, this should be taken quite literally.
 
 For writing the control register, there simply is no possible story: no Rust operation exists that would change the rounding mode of subsequent floating-point operations.

-Any inline asm block that changes the rounding mode therefore has undefined behavior.
+Any inline asm block that changes the rounding mode therefore has undefined behavior (and the same goes for other flags that change the behavior of instructions used by the Rust compiler, like flushing subnormals to zero).

 
 While this may sound bleak, it is entirely possible to write an inline asm block that changes the rounding mode, performs some floating-point operations, and then changes it back!
 The story code for this block can use a soft-float library to perform exactly the same floating-point operations with a non-default rounding mode.
 
 While this may sound bleak, it is entirely possible to write an inline asm block that changes the rounding mode, performs some floating-point operations, and then changes it back!
 The story code for this block can use a soft-float library to perform exactly the same floating-point operations with a non-default rounding mode.