[llvm] 7d71bc3 - [GlobalISel][Docs] Fix known-bits example and code snippet in KnownBits.rst (#213090)

[via llvm-commits]

Author: Kevin Le
Date: 2026-08-13T07:36:27+01:00
New Revision: 7d71bc3b7799e6cfe80f5ec6ee4ef83255a70d59

URL: https://github.com/llvm/llvm-project/commit/7d71bc3b7799e6cfe80f5ec6ee4ef83255a70d59
DIFF: https://github.com/llvm/llvm-project/commit/7d71bc3b7799e6cfe80f5ec6ee4ef83255a70d59.diff

LOG: [GlobalISel][Docs] Fix known-bits example and code snippet in KnownBits.rst (#213090)

- The simplified example annotates `%5 = G_CONSTANT i32 0x0F0` with the
value `0x00000FF0` (from %1 line); correct value is `0x000000F0`.
- `GISelValueTrackingAnalysisLegacy::get(MF)` returns a reference, so
call should be `VT.getKnownBits(...)` not `VT->getKnownBits(...)`.
- `KnownBits` members are `Zero` and `One`, not `Zeros`; use
`Known.Zero[0]` to test bit 0.

Added: 
    

Modified: 
    llvm/docs/GlobalISel/KnownBits.rst

Removed: 
    


################################################################################
diff  --git a/llvm/docs/GlobalISel/KnownBits.rst b/llvm/docs/GlobalISel/KnownBits.rst
index 3c61a58626e84..0a16a7d2825cb 100644
--- a/llvm/docs/GlobalISel/KnownBits.rst
+++ b/llvm/docs/GlobalISel/KnownBits.rst
@@ -45,7 +45,7 @@ and then use this to simplify the expression:
 .. code-block:: none
 
                                    ; %0 = 0x????????
-  %5:(s32) = G_CONSTANT i32 0x0F0  ; %5 = 0x00000FF0
+  %5:(s32) = G_CONSTANT i32 0x0F0  ; %5 = 0x000000F0
   %4:(s32) = G_AND %0, %5          ; %4 = 0x000000?0
 
 Note that ``%4`` still has the same known bits as before the transformation.
@@ -89,8 +89,8 @@ Then it's just a matter of fetching the analysis and using it:
     GISelValueTracking &VT = getAnalysis<GISelValueTrackingAnalysisLegacy>().get(MF);
     ...
     MachineInstr *MI = ...;
-    KnownBits Known = VT->getKnownBits(MI->getOperand(0).getReg());
-    if (Known.Zeros & 1) {
+    KnownBits Known = VT.getKnownBits(MI->getOperand(0).getReg());
+    if (Known.Zero[0]) {
       // Bit 0 is known to be zero
     }
     ...