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:
+  - id: csr-fflags-purpose
+    normative: true
+    text: |
+      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.
+  - id: csr-fflags-fptrap
+    normative: false
+    text: The base RISC-V ISA does not support generating a trap on the setting of a floating-point exception flag.
+  - id: csr-fflags-reasoning
+    normative: false
+    text: |
+      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:
+    alias: fcsr.NV
+    long_name: Invalid Operation
+    location: 4
+    description: |
+      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:
+    alias: fcsr.DZ
+    long_name: Divide by Zero
+    location: 3
+    description: |
+      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:
+    alias: fcsr.OF
+    long_name: Overflow
+    location: 2
+    description: |
+      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:
+    alias: fcsr.UF
+    long_name: Underflow
+    location: 1
+    description: |
+      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:
+    alias: fcsr.NX
+    long_name: Inexact
+    location: 0
+    description: |
+      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
+sw_read(): |
+  return
+   (CSR[fcsr].NV `<< 4) |
+   (CSR[fcsr].DZ `<< 3) |
+   (CSR[fcsr].OF `<< 2) |
+   (CSR[fcsr].UF `<< 1) |
+   CSR[fcsr].NX;

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:
+  - id: csr-frm-encodings
+    normative: false
+    text: |
+      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_.
+      !===
+  - id: csr-frm-reserved
+    normative: false
+    text: |
+      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).
+  - id: csr-frm-rmfield
+    normative: false
+    text: |
+      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:
+    alias: fcsr.FRM
+    location: 2-0
+    description: |
+      Rounding mode data.
+    type: RW-H
+    reset_value: UNDEFINED_LEGAL
+sw_read(): |
+  return
+   CSR[fcsr].FRM;