[llvm] IR: Introduce "float-abi" module flag (PR #210821)

[Antonio Frighetto via llvm-commits]

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@@ -9407,6 +9407,37 @@ enum is the smallest type which can represent all of its values:
 !1 = !{i32 1, !"short_enum", i32 0}
 ```
 
+### Float ABI Module Flags Metadata
+
+This module flag describes the floating-point ABI (the calling convention used
+to pass and return floating-point values) that the module was compiled for. The
+value is an `MDString` and must be one of:
+
+```{list-table}
+:header-rows: 1
+:widths: 30 70
+* - Value
+  - Meaning
+
+* - `"soft"`
+  - The software floating-point calling convention is used: floating-point
+    values are passed in general-purpose (integer) registers. Note this is
+    independent of whether floating-point hardware is used to perform
+    operations; see the `use-soft-float` function attribute for that.
----------------
antoniofrighetto wrote:

Was wondering whether this could use an example (e.g., ARM softfp already encompassed in soft here), but up to you.

https://github.com/llvm/llvm-project/pull/210821