[AArch64] Add native CPU detection for Ampere1

Map the IMPLEMENTOR ID 0xc0 (Ampere Computing) and CPU ID 0xac3
(Ampere1) to ampere1.

Differential Revision: https://reviews.llvm.org/D117111

(cherry picked from commit 7e02bc5)

Author: ptomsich

llvm/lib/Support/Host.cpp

@@ -296,6 +296,12 @@ StringRef sys::detail::getHostCPUNameForARM(StringRef ProcCpuinfoContent) {
     }
   }
 
+  if (Implementer == "0xc0") { // Ampere Computing
+    return StringSwitch<const char *>(Part)
+        .Case("0xac3", "ampere1")
+        .Default("generic");
+  }
+
   return "generic";
 }
 

llvm/unittests/Support/Host.cpp

@@ -128,6 +128,10 @@ TEST(getLinuxHostCPUName, AArch64) {
                                               "CPU part        : 0xc01"),
             "saphira");
 
+  EXPECT_EQ(sys::detail::getHostCPUNameForARM("CPU implementer : 0xc0\n"
+                                              "CPU part        : 0xac3"),
+            "ampere1");
+
   // MSM8992/4 weirdness
   StringRef MSM8992ProcCpuInfo = R"(
 Processor       : AArch64 Processor rev 3 (aarch64)