Add large code model

Signed-off-by: Jim Tsung-Chun Lin <[email protected]>

Author: tclin914

src/toolchain-conventions.adoc

@@ -108,6 +108,9 @@ within a single 2GiB address range, between the absolute addresses -2GiB and
 - `-mcmodel=medany`. The program and its statically defined symbols must lie
 within a single 4GiB address range. `auipc` and `addi` pairs are used to
 generate addresses.
+- `-mcmodel=large`. The program and its statically defined symbols can lie
+within the whole 64-bit address range. `auipc`, `addi` and `ld` are used to
+generate addresses.
 - Use of any PIC or PIE option (e.g. -fpic, -fPIC, -fpie or -fPIE) will enable
 the medium position independent code model. This model is similar to the medium
 any code model, but uses the global offset table (GOT) for non-local symbol
@@ -119,6 +122,7 @@ RISC-V psABI has a contain sections to describe the code model:
 
 - https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-elf.adoc#medium-low-code-model[Medium low code model]: -mcmodel=medlow
 - https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-elf.adoc#medium-any-code-model[Medium any code model]: -mcmodel=medany
+- https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-elf.adoc#large-code-model[Large code model]: -mcmodel=large
 - https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-elf.adoc#medium-position-independent-code-model[Medium position independent code model]:  -fpic, -fPIC, -fpie or -fPIE.
 
 == Disassembler (objdump) behaviour
@@ -172,8 +176,9 @@ toolchain defined `+__riscv__+`.
 - `+__riscv_float_abi_soft+`, `+__riscv_float_abi_single+`,
 `+__riscv_float_abi_double+`: one of these three will be defined, depending on
 target ABI.
-- `+__riscv_cmodel_medlow+`, `+__riscv_cmodel_medany+`: one of these two will be
-defined, depending on the target code model.
+- `+__riscv_cmodel_medlow+`, `+__riscv_cmodel_medany+`,
+`+__riscv_cmodel_large+`: one of these three will be defined, depending on
+the target code model.
 - `+__riscv_mul+`: defined when targeting the 'M' ISA extension.
 - `+__riscv_muldiv+`: defined when targeting the 'M' ISA extension and
 `-mno-div` has not been used.