[llvm] [llvm][MC] Fix missing SubArch information when calling lookupTarget (PR #69902)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-mc

Author: None (huaatian)

<details>
<summary>Changes</summary>

When calling the function 'lookupTarget', in some cases, the SubArch information of the parameter TheTriple gets lost. This modification ensures the integrity of the parameter TheTriple.

---
Full diff: https://github.com/llvm/llvm-project/pull/69902.diff


2 Files Affected:

- (modified) llvm/lib/MC/TargetRegistry.cpp (+2-1) 
- (modified) llvm/unittests/MC/TargetRegistry.cpp (+18) 


``````````diff
diff --git a/llvm/lib/MC/TargetRegistry.cpp b/llvm/lib/MC/TargetRegistry.cpp
index fa7aaccabcd6109..bfce3f9d4e5b363 100644
--- a/llvm/lib/MC/TargetRegistry.cpp
+++ b/llvm/lib/MC/TargetRegistry.cpp
@@ -43,7 +43,8 @@ const Target *TargetRegistry::lookupTarget(StringRef ArchName,
     // given triple.
     Triple::ArchType Type = Triple::getArchTypeForLLVMName(ArchName);
     if (Type != Triple::UnknownArch)
-      TheTriple.setArch(Type);
+      // Set the type of Arch while preserving SubArch, if any.
+      TheTriple.setArch(Type, TheTriple.getSubArch());
   } else {
     // Get the target specific parser.
     std::string TempError;
diff --git a/llvm/unittests/MC/TargetRegistry.cpp b/llvm/unittests/MC/TargetRegistry.cpp
index cc464b7681ce17e..924a55add874697 100644
--- a/llvm/unittests/MC/TargetRegistry.cpp
+++ b/llvm/unittests/MC/TargetRegistry.cpp
@@ -42,4 +42,22 @@ TEST(TargetRegistry, TargetHasArchType) {
   ASSERT_NE(Count, 0);
 }
 
+TEST(TargetRegistry, PreserveSubArchInfo) {
+  auto T = Triple("mipsisa64r6el-unknown-linux-gnuabi64");
+  EXPECT_EQ(Triple::mips64el, T.getArch());
+  EXPECT_EQ(Triple::MipsSubArch_r6, T.getSubArch());
+  EXPECT_EQ(Triple::UnknownVendor, T.getVendor());
+  EXPECT_EQ(Triple::Linux, T.getOS());
+  EXPECT_EQ(Triple::GNUABI64, T.getEnvironment());
+  std::string Error;
+  if (!TargetRegistry::lookupTarget("mips64el", T, Error))
+    GTEST_SKIP();
+  EXPECT_EQ(Triple::mips64el, T.getArch());
+  // The SubArch information needs to be preserved.
+  EXPECT_EQ(Triple::MipsSubArch_r6, T.getSubArch());
+  EXPECT_EQ(Triple::UnknownVendor, T.getVendor());
+  EXPECT_EQ(Triple::Linux, T.getOS());
+  EXPECT_EQ(Triple::GNUABI64, T.getEnvironment());
+}
+
 } // end namespace

``````````

</details>


https://github.com/llvm/llvm-project/pull/69902