Welcome, fellow adventurers, to the realm of compiler building! Today, we embark on a perilous quest to build GCC 5.4 on RISC-V, a quest fraught with danger, mystery, and… unknown modes. Fear not, for we shall vanquish the errors together and emerge victorious, our compiler built and ready to take on the world!
The Quest Begins: Preparing the Battlefield
Before we start, make sure you have the following requirements in place:
- A Linux system (we’ll assume Ubuntu 18.04 LTS for this tutorial)
- A RISC-V toolchain installed (e.g.,
riscv64-unknown-elf-gcc) - The GCC 5.4 source code (
gcc-5.4.tar.bz2) - Patience, courage, and a dash of coding wizardry
Downloading and Extracting the GCC 5.4 Source Code
Fetch the GCC 5.4 source code from the official GNU website (https://ftp.gnu.org/gnu/gcc/gcc-5.4.0/gcc-5.4.0.tar.bz2) and extract it to a directory of your choice:
wget https://ftp.gnu.org/gnu/gcc/gcc-5.4.0/gcc-5.4.0.tar.bz2
tar -xvf gcc-5.4.0.tar.bz2
Configuring the Build Environment
Create a build directory (gcc-build) and navigate into it:
mkdir gcc-build
cd gcc-build
Configure the build environment using the following command:
../gcc-5.4.0/configure --target=riscv64-unknown-elf --prefix=/usr/local/riscv --enable-languages=c,c++ --disable-multilib
Note the --target parameter, which specifies the target architecture as RISC-V. The --prefix parameter sets the installation directory to /usr/local/riscv.
The Fateful Build Command
Execute the build command:
make -j4
This command will start the build process, which may take several hours to complete, depending on your system’s resources. You can adjust the -j4 parameter to control the number of parallel build jobs.
The Error Strikes: “Unknown Mode ‘TF'”
As you wait for the build to complete, an error message may appear:
/home/user/gcc-5.4.0/gcc/config/riscv/riscv.md:143: Unknown mode `TF' for insn
make[1]: *** [gcc/insn-emit.o] Error 1
make[1]: Leaving directory `/home/user/gcc-build/gcc'
make: *** [all-gcc] Error 2
Fear not, brave adventurer! This error is a common obstacle on the path to building GCC 5.4 on RISC-V.
Understanding the “Unknown Mode ‘TF'” Error
The error message indicates that the compiler encounters an unknown instruction mode ‘TF’ while processing the RISC-V architecture description file (riscv.md). This mode is specific to the RISC-V instruction set and is not supported in GCC 5.4.
Taming the “Unknown Mode ‘TF'” Error
To resolve this error, we’ll need to modify the riscv.md file to remove the references to the ‘TF’ mode. Create a patch file (riscv_tf_patch.diff) with the following contents:
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -140,7 +140,7 @@
(define_insn "movti"
[(set (match_operand:TI 0 "register_operand" "=r")
(match_operand:TI 1 "immediate_operand" "i"))]
- "TF"
+ ""
"mov\t%0, %1"
)
Apply the patch using the following command:
patch -p1 < riscv_tf_patch.diff
This patch removes the 'TF' mode from the riscv.md file, allowing the build to continue.
Resuming the Build
After applying the patch, resume the build process:
make -j4
The build should now complete successfully.
Installing the GCC 5.4 Compiler
Install the built compiler to the specified prefix directory:
make install
This command will install the GCC 5.4 compiler and its dependencies to /usr/local/riscv.
Verifying the Installation
Verify that the installation was successful by checking the version of the installed compiler:
/usr/local/riscv/bin/riscv64-unknown-elf-gcc --version
You should see the GCC 5.4 version information:
riscv64-unknown-elf-gcc (GCC) 5.4.0
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Conclusion: The Victory Cry
With the "Unknown Mode 'TF'" error vanquished, we have successfully built and installed GCC 5.4 on RISC-V. Our compiler is now ready to tackle the challenges of building and compiling code for the RISC-V architecture.
Celebrate your victory, brave adventurer, for you have conquered the realm of compiler building! May your future endeavors be filled with wisdom, courage, and error-free builds!
| GCC Version | RISC-V Architecture | Error Resolution |
|---|---|---|
| 5.4 | RISC-V | Patch riscv.md to remove 'TF' mode |
Remember, in the realm of compiler building, knowledge is power, and patience is a virtue. May your builds be long-lived and error-free!
Happy coding, brave adventurers!
Frequently Asked Question
If you're struggling to build GCC 5.4 on RISC-V and encountering the mysterious "unknown mode 'TF'" error, worry not! We've got you covered with these FAQs.
Q1: What does the "unknown mode 'TF'" error mean?
Aha! The "unknown mode 'TF'" error means that the GCC compiler is unfamiliar with the 'TF' mode, which is a specific instruction mode used in RISC-V. This is likely due to the GCC version being too old to recognize this mode.
Q2: Why does GCC 5.4 not support 'TF' mode?
GCC 5.4 is an older version of the compiler, released before the 'TF' mode was introduced in the RISC-V ISA. That's why it doesn't recognize this mode, resulting in the error.
Q3: Can I fix the error by updating my GCC version?
Yes, you can! Updating to a newer version of GCC, such as GCC 7 or later, which supports the 'TF' mode, should resolve the issue. Alternatively, you can also try patching the GCC 5.4 source code to add support for the 'TF' mode, but that might be more complicated.
Q4: Are there any other RISC-V ISA modes that might cause similar issues?
Yes, you might encounter similar issues with other RISC-V ISA modes, such as 'D' or 'F' modes, depending on the specific GCC version and RISC-V architecture you're targeting. Be prepared to investigate and potentially update your GCC version or apply patches to support these modes.
Q5: What are the implications of using an older GCC version for RISC-V development?
Using an older GCC version can lead to compatibility issues, performance limitations, and potential security vulnerabilities. It's recommended to use a recent GCC version that supports the latest RISC-V ISA features and modes to ensure optimal performance, security, and compatibility.
