[AArch64] Add Exynos to host detection

[zturner]

llvm/lib/Support/Host.cpp

222

Can you initialize Exynos to some value here?

233–234

How about

if (I.consume_front("CPU part"))
  I.ltrim("\t :").getAsInteger(16, Part);

As an example of why I prefer consume_front, it fixes what appears to be above in the preceding if statement (about CPU variant), where you've hardcoded 8 but actually meant 11.

236

Can you move the declaration of Exynos down here and just say:

unsigned Exynos = (Variant << 12) + Part;

That also simultaneously addresses my previous comment about initialization.

[evandro]

llvm/lib/Support/Host.cpp

233–234

Makes sense.

[evandro]

Thanks, @zturner.

[kristof.beyls]

LGTM modulo the one nitpick for which I'm not sure if it is needed.

llvm/lib/Support/Host.cpp

237–241

I guess you may need to use LLVM_FALLTHROUGH here to silence a warning with some compilers?

[evandro]

Thanks, @kristof.beyls.

llvm/lib/Support/Host.cpp

for (unsigned I = 0, E = Lines.size(); I != E; ++I)
             .Case("0x205", "kryo")
             .Case("0x211", "kryo")
             .Case("0x800", "cortex-a73")
             .Case("0x801", "cortex-a73")
             .Case("0xc00", "falkor")
             .Case("0xc01", "saphira")
             .Default("generic");
 
+  if (Implementer == "0x53") { // Samsung Electronics Co., Ltd.
+    // The Exynos chips have a convoluted ID scheme that doesn't seem to follow
+    // any predictive pattern across variants and parts.
+    unsigned Variant = 0, Part = 0;
+
+    // Look for the CPU variant line, whose value is a 1 digit hexadecimal
+    // number, corresponding to the Variant bits in the CP15/C0 register.
+    for (auto I : Lines)
+      if (I.consume_front("CPU variant"))
+        I.ltrim("\t :").getAsInteger(16, Variant);
+
+    // Look for the CPU part line, whose value is a 3 digit hexadecimal
+    // number, corresponding to the PartNum bits in the CP15/C0 register.
+    for (auto I : Lines)
+      if (I.consume_front("CPU part"))
+        I.ltrim("\t :").getAsInteger(16, Part);
+
+    unsigned Exynos = (Variant << 12) + Part;
+    switch (Exynos) {
+    default:
+      // Default to Exynos M1.
+
+    case 0x01001:
+      return "exynos-m1";
+
+    case 0x04001:
+      return "exynos-m2";
+    }
+  }
+
   return "generic";
 }
 
 StringRef sys::detail::getHostCPUNameForS390x(
     const StringRef &ProcCpuinfoContent) {
   // STIDP is a privileged operation, so use /proc/cpuinfo instead.
 
   // The "processor 0:" line comes after a fair amount of other information,

llvm/unittests/Support/Host.cpp

 CPU part        : 0xd03
 CPU revision    : 3
 
 Hardware        : Qualcomm Technologies, Inc MSM8992
 )";
 
   EXPECT_EQ(sys::detail::getHostCPUNameForARM(MSM8992ProcCpuInfo),
             "cortex-a53");
+
+  // Exynos big.LITTLE weirdness
+  const std::string ExynosProcCpuInfo = R"(
+processor       : 0
+Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32
+CPU implementer : 0x41
+CPU architecture: 8
+CPU variant     : 0x0
+CPU part        : 0xd03
+
+processor       : 1
+Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32
+CPU implementer : 0x53
+CPU architecture: 8
+)";
+
+  EXPECT_EQ(sys::detail::getHostCPUNameForARM(ExynosProcCpuInfo +
+                                              "CPU variant     : 0x1\n"
+                                              "CPU part        : 0x001"),
+            "exynos-m1");
+  EXPECT_EQ(sys::detail::getHostCPUNameForARM(ExynosProcCpuInfo +
+                                              "CPU variant     : 0x4\n"
+                                              "CPU part        : 0x001"),
+            "exynos-m2");
+  // Verify default for Exynos.
+  EXPECT_EQ(sys::detail::getHostCPUNameForARM(ExynosProcCpuInfo +
+                                              "CPU variant     : 0xc\n"
+                                              "CPU part        : 0xafe"),
+            "exynos-m1");
 }
 
 #if defined(__APPLE__)
 TEST_F(HostTest, getMacOSHostVersion) {
   using namespace llvm::sys;
   llvm::Triple HostTriple(getProcessTriple());
   if (!HostTriple.isMacOSX())
     return;