[llvm] [IR] Add llvm `cmul` intrinsic (PR #140301)

[Jay Foad via llvm-commits]

================
@@ -18055,6 +18055,54 @@ Example:
       %r = call i8 @llvm.fshr.i8(i8 15, i8 15, i8 11)  ; %r = i8: 225 (0b11100001)
       %r = call i8 @llvm.fshr.i8(i8 0, i8 255, i8 8)   ; %r = i8: 255 (0b11111111)
 
+.. clmul:
+
+'``clmul.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.clmul``
+on any integer bit width or vectors of integers.
+
+::
+
+      declare i16 @llvm.clmul.i16(i16 %a, i16 %b)
+      declare i32 @llvm.clmul.i32(i32 %a, i32 %b)
+      declare i64 @llvm.clmul.i64(i64 %a, i64 %b)
+      declare <4 x i32> @llvm.clmul.v4i32(<4 x i32> %a, <4 x i32> %b)
+
+Overview
+"""""""""
+
+The '``llvm.clmul``' family of intrinsics functions perform carryless multiplication
----------------
jayfoad wrote:

```suggestion
The '``llvm.clmul``' family of intrinsic functions performs carryless multiplication
```

https://github.com/llvm/llvm-project/pull/140301