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@ -167,7 +167,7 @@ rustc \
<tr><td style="text-align: left"><em>-mabi</em> <br>     <strong>ilp32d</strong></td><td style="text-align: left"></td></tr>
</tbody></table>
</div></span>
<p><em>Hmmm something different about the Floats…</em></p>
<p><em>Hmmm the Floats look different…</em></p>
<p>Yep GCC compiles for (Double-Precision) <strong>Hardware Floating-Point</strong>…</p>
<p>But Rust Compiler uses <strong>Software Floating-Point</strong>!</p>
<span style="font-size:90%">
@ -213,7 +213,7 @@ Flags: 0x0
<p>“<strong><code>gc</code></strong>” in “<strong><code>riscv32gc</code></strong>” denotes <a href="https://en.wikipedia.org/wiki/RISC-V#ISA_base_and_extensions"><strong>IMAFDC</strong></a></p>
</li>
</ul>
<p>So we could do this…</p>
<p>Hence we could do this…</p>
<div class="example-wrap"><pre class="language-bash"><code>## Compile `hello_rust_main.rs` to `hello_rust.o`
## for Double-Precision Hardware Floating-Point
rustc \
@ -226,7 +226,7 @@ rustc \
hello_rust_main.rs \
-o hello_rust.o
</code></pre></div>
<p>Nope sorry it won’t work…</p>
<p>Sorry nope it <strong>won’t work</strong>…</p>
<div class="example-wrap"><pre class="language-bash"><code>Error loading target specification:
Could not find specification for target &quot;riscv32gc-unknown-none-elf&quot;.
Run `rustc --print target-list` for a list of built-in targets
@ -243,7 +243,8 @@ riscv64gc-unknown-linux-gnu
riscv64gc-unknown-none-elf
riscv64imac-unknown-none-elf
</code></pre></div>
<p>But we can create a <strong>Custom Rust Target</strong> for <strong><code>riscv32gc</code></strong>. Coming up next section!</p>
<p>But we can create a <strong>Custom Rust Target</strong> for <strong><code>riscv32gc</code></strong>.</p>
<p>(Coming up next section)</p>
<p><em>Won’t GCC Compiler have the same problem with Double-Float?</em></p>
<p>When we list the <strong>Built-In GCC Targets</strong>…</p>
<div class="example-wrap"><pre class="language-bash"><code>## List the Built-In Targets for GCC RISC-V.
@ -265,6 +266,7 @@ riscv64-unknown-elf-gcc \
-mabi=ilp32d \
...
</code></pre></div>
<p>We’ll make something similar for Rust Compiler…</p>
<p><a href="https://gcc.gnu.org/onlinedocs/gcc/RISC-V-Options.html#index-mabi-5">(More about <strong>Application Binary Interfaces</strong>)</a></p>
<p><img src="https://lupyuen.github.io/images/rust4-flow1a.jpg" alt="Custom Target for Rust" /></p>
<h1 id="custom-target-for-rust"><a class="doc-anchor" href="#custom-target-for-rust">§</a>3 Custom Target for Rust</h1>
@ -307,8 +309,8 @@ $ rustc \
&quot;target-pointer-width&quot;: &quot;32&quot;
}
</code></pre></div>
<p>That’s the Rust Definition of <a href="TODO"><strong><code>riscv32i</code></strong></a>: 32-bit RISC-V with Soft-Float.</p>
<p>We do the same for <a href="TODO"><strong><code>riscv64gc</code></strong></a>: 64-bit RISC-V with Double-Float…</p>
<p>That’s the Rust Definition of <a href="TODO"><strong><code>riscv32i</code></strong></a>: <strong>32-bit</strong> RISC-V with <strong>Soft-Float</strong>.</p>
<p>We do the same for <a href="TODO"><strong><code>riscv64gc</code></strong></a>: <strong>64-bit</strong> RISC-V with <strong>Double-Float</strong>…</p>
<div class="example-wrap"><pre class="language-bash"><code>## Dump the Built-In Rust Target:
## riscv64gc (64-bit RISC-V with Hard-Float)
$ rustc \
@ -368,7 +370,7 @@ $ rustc \
</li>
<li>
<p>Add <em>“features”: “+m,+a,+f,+d,+c”</em></p>
<p>TODO</p>
<p><a href="TODO">(Because we need <strong>IMAFDC</strong>)</a></p>
</li>
<li>
<p>Add <em>“llvm-abiname”: “ilp32d”</em></p>
@ -376,9 +378,9 @@ $ rustc \
<p><a href="https://lupyuen.github.io/articles/rust#custom-rust-target-for-bl602">(More about <strong><code>llvm-abiname</code></strong>)</a></p>
</li>
</ul>
<p>Once Again: Here’s how we splice the Two Built-In Targets to create our Custom Target <strong><code>riscv32gc</code></strong>…</p>
<p>Once Again: We spliced the Two Built-In Targets to make Custom Target <strong><code>riscv32gc</code></strong>…</p>
<span style="font-size:80%">
<div><table><thead><tr><th></th><th style="text-align: center"><a href="TODO">riscv32i</a></th><th style="text-align: center"><a href="TODO">riscv64gc</a></th><th style="text-align: center"><a href="TODO">riscv32gc</a></th></tr></thead><tbody>
<div><table><thead><tr><th></th><th style="text-align: center"><a href="TODO">riscv32i</a> <br> <em>(Built-In)</em></th><th style="text-align: center"><a href="TODO">riscv64gc</a> <br> <em>(Built-In)</em></th><th style="text-align: center"><a href="TODO">riscv32gc</a> <br> <em>(Custom)</em></th></tr></thead><tbody>
<tr><td><em>arch</em></td><td style="text-align: center"><strong>riscv32</strong></td><td style="text-align: center">riscv64</td><td style="text-align: center"><strong>riscv32</strong></td></tr>
<tr><td><em>atomic-cas</em></td><td style="text-align: center">false</td><td style="text-align: center"></td><td style="text-align: center"></td></tr>
<tr><td><em>cpu</em></td><td style="text-align: center"><strong>generic-rv32</strong></td><td style="text-align: center">generic-rv64</td><td style="text-align: center"><strong>generic-rv32</strong></td></tr>
@ -395,8 +397,8 @@ $ rustc \
<p><img src="https://lupyuen.github.io/images/rust4-flow1b.jpg" alt="Build the Rust Core Library" /></p>
</blockquote>
<h1 id="build-the-rust-core-library"><a class="doc-anchor" href="#build-the-rust-core-library">§</a>4 Build the Rust Core Library</h1>
<p><em>We’re ready to rebuild with Double-Float?</em></p>
<p>Not quite, we’re not done with the <strong>System Library</strong>!</p>
<p><em>Are we ready to rebuild with Double-Float?</em></p>
<p>Not quite, we’re not done with the <strong>System Library</strong>…</p>
<div class="example-wrap"><pre class="language-bash"><code>## Rust Compiler fails to compile with our Custom Target `riscv32gc`
$ rustc \
--target riscv32gc-unknown-none-elf.json \
@ -415,11 +417,11 @@ error[E0463]: can&#39;t find crate for `core`
<ul>
<li>
<p><strong>GCC Compiler</strong> supports Double-Float…</p>
<p>Because it’s bundled with <strong>C Standard Library</strong> for Double-Float, thus…</p>
<p>Because it’s bundled with <strong>C Standard Library</strong> for Double-Float</p>
</li>
<li>
<p><strong>Rust Compiler</strong> will support Double-Float…</p>
<p>Only when it has the <a href="TODO"><strong>Rust Core Library</strong></a> for Double-Float!</p>
<p>Thus <strong>Rust Compiler</strong> will support Double-Float…</p>
<p>Only when it has the <a href="TODO"><strong>Rust Core Library</strong></a> for Double-Float</p>
</li>
</ul>
<p><em>And the Rust Core Library comes from?</em></p>
@ -466,7 +468,7 @@ librustc_std_workspace_core-3cc5bcc9f701a6e7.rlib
librustc_std_workspace_core-3cc5bcc9f701a6e7.rmeta
rustc_std_workspace_core-3cc5bcc9f701a6e7.d
</code></pre></div>
<p>Now we’re ready to <strong>rebuild our Rust App</strong> with the Custom Target (linked to our Rust Core Library)…</p>
<p>Now we <strong>rebuild our Rust App</strong> with the Custom Target (linked to our Rust Core Library)…</p>
<div class="example-wrap"><pre class="language-bash"><code>## Compile our Rust App with Rust Core Library for `riscv32gc`
## We changed the Target to `riscv32gc-unknown-none-elf.json`
## TODO: Change `../apps` to the NuttX Apps Folder
@ -490,7 +492,7 @@ rustc \
</code></pre></div>
<p>(We’ll talk about the loooong options)</p>
<p><em>Are we Double-Floating yet?</em></p>
<p>Yep we have a <strong>Yummy Double-Float</strong> with 2 scoops of ice cream!</p>
<p>Yep we have a <strong>Yummy Double-Float</strong> with 2 scoops of ice cream…</p>
<div class="example-wrap"><pre class="language-bash"><code>## Dump the ELF Header of our Compiled Rust App
## TODO: Change `../apps` to the NuttX Apps Folder
$ riscv64-unknown-elf-readelf \
@ -654,7 +656,7 @@ rustc \
-Z unstable-options
</code></pre></div>
<p>We copied the above options from <strong><code>cargo build -v</code></strong>, here’s how…</p>
<p>Remember Earlier: We ran <a href="TODO"><strong><code>cargo build</code></strong></a> to compile the <a href="TODO"><strong>Rust Core Library</strong></a>…</p>
<p>Remember we ran <a href="TODO"><strong><code>cargo build</code></strong></a> to compile the <a href="TODO"><strong>Rust Core Library</strong></a>?</p>
<div class="example-wrap"><pre class="language-bash"><code>## Build the Rust Core Library for `riscv32gc`
$ cargo build \
-Zbuild-std=core,alloc \