[libcxx] [llvm] Triple::normalize: Set OS for 3-component triple with none as middle (PR #89638)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: YunQiang Su (wzssyqa)

<details>
<summary>Changes</summary>

If the middle component of a 3-component triple fails to parse as known Arch/Vendor/OS/Env, it will fallback as Vendor. While for some cases, we may wish to recognize it as OS, such as `arm64-none-elf`.

In this patch, we will set OS as `none`, if:
	1) Arch is found;
	2) Env is found;
	3) OS is not found and thus is set as empty;
	4) Vendor is not found while is set as "none",
we will swap Component[2] and Component[3].

Fixes: #<!-- -->89582.

---
Full diff: https://github.com/llvm/llvm-project/pull/89638.diff


2 Files Affected:

- (modified) libcxx/utils/ci/run-buildbot (+1-1) 
- (modified) llvm/lib/TargetParser/Triple.cpp (+7) 


``````````diff
diff --git a/libcxx/utils/ci/run-buildbot b/libcxx/utils/ci/run-buildbot
index 60307a7d4f350a..3523a29e4f4613 100755
--- a/libcxx/utils/ci/run-buildbot
+++ b/libcxx/utils/ci/run-buildbot
@@ -217,7 +217,7 @@ function test-armv7m-picolibc() {
         "${@}"
 
     ${NINJA} -vC "${BUILD_DIR}/compiler-rt" install
-    mv "${BUILD_DIR}/install/lib/armv7m-none-unknown-eabi"/* "${BUILD_DIR}/install/lib"
+    mv "${BUILD_DIR}/install/lib/armv7m-unknown-none-eabi"/* "${BUILD_DIR}/install/lib"
 
     check-runtimes
 }
diff --git a/llvm/lib/TargetParser/Triple.cpp b/llvm/lib/TargetParser/Triple.cpp
index 77fdf31d4865c0..07f3df4145dad4 100644
--- a/llvm/lib/TargetParser/Triple.cpp
+++ b/llvm/lib/TargetParser/Triple.cpp
@@ -1149,6 +1149,13 @@ std::string Triple::normalize(StringRef Str) {
     }
   }
 
+  // For 3-component triples, the middle component is used to set Vendor;
+  // while if it is "none", we'd prefer to set OS.
+  // This is for some baremetal cases, such as "arm-none-elf".
+  if (Found[0] && !Found[1] && !Found[2] && Found[3] &&
+      Components[1].equals("none") && Components[2].empty())
+    std::swap(Components[1], Components[2]);
+
   // Replace empty components with "unknown" value.
   for (StringRef &C : Components)
     if (C.empty())

``````````

</details>


https://github.com/llvm/llvm-project/pull/89638