Add FFLAGS and FRM CSRs

arch/csr/F/fflags.yaml

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+# yaml-language-server: $schema=../../../schemas/csr_schema.json
+
+$schema: "csr_schema.json#"
+kind: csr
+name: fflags
+long_name: Floating-Point Accrued Exceptions
+address: 0x001
+description: |
+  The accrued exception flags indicate the exception conditions that have arisen on any floating-point
+  arithmetic instruction since the field was last reset by software. The base RISC-V ISA does not
+  support generating a trap on the setting of a floating-point exception flag.
+
+  [[rm]]
+  .Accrued Exception Flag Encoding.
+  [%autowidth,float="center",align="center",cols="^,^,<",options="header"]
+  !===
+  !Flag Mnemonic |Flag Meaning
+  !NV !Invalid Operation
+  !DZ !Divide by Zero
+  !OF !Overflow
+  !UF !Underflow
+  !NX !Inexact
+  !===
+
+  As allowed by the standard, we do not support traps on floating-point exceptions in the F
+  extension, but instead require explicit checks of the flags in software. We considered
+  adding branches controlled directly by the contents of the floating-point accrued exception
+  flags, but ultimately chose to omit these instructions to keep the ISA simple.
+
+priv_mode: U
+length: 32
+definedBy: F
+fields:
+  NV:
+    location: 4
+    description: |
+      *Invalid Operation*
+
+      Cumulative error flag for floating point operations.
+
+      Set by hardware when a floating point operation is invalid and stays set until explicitly
+      cleared by software.
+    type: RW-H
+    reset_value: UNDEFINED_LEGAL
+  DZ:
+    location: 3
+    description: |
+      *Divide by zero*
+
+      Cumulative error flag for floating point operations.
+
+      Set by hardware when a floating point divide attempts to divide by zero and stays set until explicitly
+      cleared by software.
+    type: RW-H
+    reset_value: UNDEFINED_LEGAL
+  OF:
+    location: 2
+    description: |
+      *Overflow*
+
+      Cumulative error flag for floating point operations.
+
+      Set by hardware when a floating point operation overflows and stays set until explicitly
+      cleared by software.
+    type: RW-H
+    reset_value: UNDEFINED_LEGAL
+  UF:
+    location: 1
+    description: |
+      *Underflow*
+
+      Cumulative error flag for floating point operations.
+
+      Set by hardware when a floating point operation underflows and stays set until explicitly
+      cleared by software.
+    type: RW-H
+    reset_value: UNDEFINED_LEGAL
+  NX:
+    location: 0
+    description: |
+      *Inexact*
+
+      Cumulative error flag for floating point operations.
+
+      Set by hardware when a floating point operation is inexact and stays set until explicitly
+      cleared by software.
+    type: RW-H
+    reset_value: UNDEFINED_LEGAL

arch/csr/F/frm.yaml

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+# yaml-language-server: $schema=../../../schemas/csr_schema.json
+
+$schema: "csr_schema.json#"
+kind: csr
+name: frm
+long_name: Floating-Point Dynamic Rounding Mode
+address: 0x002
+description: |
+  Rounding modes are encoded as follows:
+
+  [[rm]]
+  .Rounding mode encoding.
+  [%autowidth,float="center",align="center",cols="^,^,<",options="header"]
+  !===
+  !Rounding Mode |Mnemonic |Meaning
+  !000 !RNE !Round to Nearest, ties to Even
+  !001 !RTZ !Round towards Zero
+  !010 !RDN !Round Down (towards latexmath:[$-\infty$])
+  !011 !RUP !Round Up (towards latexmath:[$+\infty$])
+  !100 !RMM !Round to Nearest, ties to Max Magnitude
+  !101 ! !_Reserved for future use._
+  !110 ! !_Reserved for future use._
+  !111 !DYN !In instruction's _rm_ field, selects dynamic rounding mode; In Rounding Mode register, _reserved_.
+  !===
+
+  A value of 111 in the
+  instruction's _rm_ field selects the dynamic rounding mode held in
+  `frm`. The behavior of floating-point instructions that depend on
+  rounding mode when executed with a reserved rounding mode is _reserved_,
+  including both static reserved rounding modes (101-110) and dynamic reserved
+  rounding modes (101-111). Some instructions, including widening conversions,
+  have the _rm_ field but are nevertheless mathematically unaffected by the
+  rounding mode; software should set their _rm_ field to
+  RNE (000) but implementations must treat the _rm_ field as usual (in
+  particular, with regard to decoding legal vs. reserved encodings).
+
+priv_mode: U
+length: 32
+definedBy: F
+fields:
+  ROUNDINGMODE:
+    location: 2-0
+    description: |
+      Rounding mode data.
+    type: RW-H
+    reset_value: UNDEFINED_LEGAL