arch: riscv: Add Zc* compressed instruction extension support

This commit adds the support for the following new Zc* series compressed
instruction extensions:

  Zca  - Subset of the C extension without FP loads and stores
  Zcb  - "Simple" instructions
  Zcd  - Double-precision floating-point instructions
  Zcf  - Single-precision floating-point instructions
  Zcmp - "Complex" instructions for embedded CPUs
  Zcmt - Table jump instructions for embedded CPUs

With the introduction of the Zc* extensions, the C extension now implies
the following Zc* extensions:

  * Zca, always
  * Zcf if F is specified (RV32 only)
  * Zcd if D is specified

The Zc* extensions that are implied by the C extension are not specified in
the GCC `-march` flag because they are redundant and can interfere with the
resolution of the correct multi-lib for the selected architecture unless
the the alternate mappings for the redundant forms are manually specified.

All the implementation details in this commit are based on the Zc* v1.0.0
specification, which is the ratified version.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

Author: stephanosio

arch/riscv/Kconfig.isa

@@ -89,6 +89,9 @@ config RISCV_ISA_EXT_Q
 
 config RISCV_ISA_EXT_C
 	bool
+	select RISCV_ISA_EXT_ZCA
+	select RISCV_ISA_EXT_ZCD if RISCV_ISA_EXT_D
+	select RISCV_ISA_EXT_ZCF if RISCV_ISA_EXT_F && (RISCV_ISA_RV32I || RISCV_ISA_RV32E)
 	help
 	  (C) - Standard Extension for Compressed Instructions
 
@@ -127,6 +130,65 @@ config RISCV_ISA_EXT_ZALRSC
 
 	  The Zalrsc extension enables support for LR.W/D and SC.W/D-style instructions.
 
+config RISCV_ISA_EXT_ZCA
+	bool
+	help
+	  (Zca) - Zba Extension for Compressed Instructions
+
+	  The Zca extension is a subset of the C extension that does not include
+	  the floating-point load and store instructions.
+
+config RISCV_ISA_EXT_ZCB
+	bool
+	depends on RISCV_ISA_EXT_ZCA
+	help
+	  (Zcb) - Zcb Extension for Simple Compressed Instructions
+
+	  The Zcb extension is a set of simple code-size saving instructions
+	  which are easy to implement on all CPUs.
+
+config RISCV_ISA_EXT_ZCD
+	bool
+	depends on RISCV_ISA_EXT_D
+	depends on RISCV_ISA_EXT_ZCA
+	help
+	  (Zcd) - Zcd Extension for Double-Precision FP Compressed Instructions
+
+	  The Zcd extension consists of compressed double-precision
+	  floating-point load and store instructions.
+
+config RISCV_ISA_EXT_ZCF
+	bool
+	depends on RISCV_ISA_RV32I || RISCV_ISA_RV32E
+	depends on RISCV_ISA_EXT_F
+	depends on RISCV_ISA_EXT_ZCA
+	help
+	  (Zcf) - Zcf Extension for Single-Precision FP Compressed Instructions
+
+	  The Zcf extension consists of compressed single-precision
+	  floating-point load and store instructions.
+
+config RISCV_ISA_EXT_ZCMP
+	bool
+	depends on RISCV_ISA_EXT_ZCA
+	depends on !RISCV_ISA_EXT_ZCD
+	help
+	  (Zcmp) - Zcmp Extension for Complex Compressed Instructions
+
+	  The Zcmp extension consists of complex operations intended for
+	  embedded CPUs.
+
+config RISCV_ISA_EXT_ZCMT
+	bool
+	depends on RISCV_ISA_EXT_ZICSR
+	depends on RISCV_ISA_EXT_ZCA
+	depends on !RISCV_ISA_EXT_ZCD
+	help
+	  (Zcmt) - Zcmt Extension for Compressed Table Jump Instructions
+
+	  The Zcmt extension consists of compressed table jump instructions for
+	  embedded CPUs.
+
 config RISCV_ISA_EXT_ZBA
 	bool
 	help

cmake/compiler/gcc/target_riscv.cmake

@@ -66,6 +66,36 @@ if(NOT CONFIG_RISCV_ISA_EXT_A)
   endif()
 endif()
 
+# Zca is implied by C
+if(CONFIG_RISCV_ISA_EXT_ZCA AND
+   NOT CONFIG_RISCV_ISA_EXT_C)
+  string(CONCAT riscv_march ${riscv_march} "_zca")
+endif()
+
+if(CONFIG_RISCV_ISA_EXT_ZCB)
+  string(CONCAT riscv_march ${riscv_march} "_zcb")
+endif()
+
+# Zcd is implied by C+D
+if(CONFIG_RISCV_ISA_EXT_ZCD AND
+   NOT (CONFIG_RISCV_ISA_EXT_C AND CONFIG_RISCV_ISA_EXT_D))
+  string(CONCAT riscv_march ${riscv_march} "_zcd")
+endif()
+
+# Zcf is implied by C+F
+if(CONFIG_RISCV_ISA_EXT_ZCF AND
+   NOT (CONFIG_RISCV_ISA_EXT_C AND CONFIG_RISCV_ISA_EXT_F))
+  string(CONCAT riscv_march ${riscv_march} "_zcf")
+endif()
+
+if(CONFIG_RISCV_ISA_EXT_ZCMP)
+  string(CONCAT riscv_march ${riscv_march} "_zcmp")
+endif()
+
+if(CONFIG_RISCV_ISA_EXT_ZCMT)
+  string(CONCAT riscv_march ${riscv_march} "_zcmt")
+endif()
+
 if(CONFIG_RISCV_ISA_EXT_ZBA)
   string(CONCAT riscv_march ${riscv_march} "_zba")
 endif()