[LLDB] Avoid triple corruption while merging core info from platform and target triples

[omjavaid]

Summary

This patch fixes a bug where when target triple created from elf information is arm-*-linux-eabihf and platform triple is armv8l-*-linux-gnueabihf. Merging both triple results in armv8l--unknown-unknown.

This happens because we order a triple update while calling CoreUpdated and CoreUpdated creates a new triple with no vendor or environment information.

Making sure we do not update triple and just update to more specific core fixes the issue.

[labath]

Can you add a test case for this? I assuming it could be similar to one of the existing ArchSpec::MergeFrom tests in https://github.com/llvm/llvm-project/blob/7dd7a3607596a51044b8706ebf6df2e613ce1e9b/lldb/unittests/Utility/ArchSpecTest.cpp#L137

[omjavaid]

Added a unittest as suggested by @labath.

[labath]

Thanks. This behavior makes sense to me. @jasonmolenda, @clayborg, do you see any problems with this?

[omjavaid]

Ping @jasonmolenda

Any comments or LGTM?

[jasonmolenda]

Thanks for the ping, yes this looks good to me.

lldb/source/Utility/ArchSpec.cpp

void ArchSpec::MergeFrom(const ArchSpec &other) {
   // If this and other are both arm ArchSpecs and this ArchSpec is a generic
   // "some kind of arm" spec but the other ArchSpec is a specific arm core,
   // adopt the specific arm core.
   if (GetTriple().getArch() == llvm::Triple::arm &&
       other.GetTriple().getArch() == llvm::Triple::arm &&
       IsCompatibleMatch(other) && GetCore() == ArchSpec::eCore_arm_generic &&
       other.GetCore() != ArchSpec::eCore_arm_generic) {
     m_core = other.GetCore();
-    CoreUpdated(true);
+    CoreUpdated(false);
   }
   if (GetFlags() == 0) {
     SetFlags(other.GetFlags());
   }
 }
 
 bool ArchSpec::SetArchitecture(ArchitectureType arch_type, uint32_t cpu,
                                uint32_t sub, uint32_t os) {

lldb/unittests/Utility/ArchSpecTest.cpp

TEST(ArchSpecTest, MergeFrom) {
     A.MergeFrom(B);
     EXPECT_EQ(llvm::Triple::ArchType::arm, A.GetTriple().getArch());
     EXPECT_EQ(llvm::Triple::VendorType::UnknownVendor,
               A.GetTriple().getVendor());
     EXPECT_EQ(llvm::Triple::OSType::Linux, A.GetTriple().getOS());
     EXPECT_EQ(llvm::Triple::EnvironmentType::UnknownEnvironment,
               A.GetTriple().getEnvironment());
   }
+  {
+    ArchSpec A("arm--linux-eabihf");
+    ArchSpec B("armv8l--linux-gnueabihf");
+
+    EXPECT_TRUE(A.IsValid());
+    EXPECT_TRUE(B.IsValid());
+
+    EXPECT_EQ(llvm::Triple::ArchType::arm, A.GetTriple().getArch());
+    EXPECT_EQ(llvm::Triple::ArchType::arm, B.GetTriple().getArch());
+
+    EXPECT_EQ(ArchSpec::eCore_arm_generic, A.GetCore());
+    EXPECT_EQ(ArchSpec::eCore_arm_armv8l, B.GetCore());
+
+    EXPECT_EQ(llvm::Triple::VendorType::UnknownVendor,
+              A.GetTriple().getVendor());
+    EXPECT_EQ(llvm::Triple::VendorType::UnknownVendor,
+              B.GetTriple().getVendor());
+
+    EXPECT_EQ(llvm::Triple::OSType::Linux, A.GetTriple().getOS());
+    EXPECT_EQ(llvm::Triple::OSType::Linux, B.GetTriple().getOS());
+
+    EXPECT_EQ(llvm::Triple::EnvironmentType::EABIHF,
+              A.GetTriple().getEnvironment());
+    EXPECT_EQ(llvm::Triple::EnvironmentType::GNUEABIHF,
+              B.GetTriple().getEnvironment());
+
+    A.MergeFrom(B);
+    EXPECT_EQ(llvm::Triple::ArchType::arm, A.GetTriple().getArch());
+    EXPECT_EQ(ArchSpec::eCore_arm_armv8l, A.GetCore());
+    EXPECT_EQ(llvm::Triple::VendorType::UnknownVendor,
+              A.GetTriple().getVendor());
+    EXPECT_EQ(llvm::Triple::OSType::Linux, A.GetTriple().getOS());
+    EXPECT_EQ(llvm::Triple::EnvironmentType::EABIHF,
+              A.GetTriple().getEnvironment());
+  }
 }
 
 TEST(ArchSpecTest, MergeFromMachOUnknown) {
   class MyArchSpec : public ArchSpec {
   public:
     MyArchSpec() {
       this->SetTriple("unknown-mach-64");
       this->m_core = ArchSpec::eCore_uknownMach64;