[AIX] Update default arch on AIX

[stevewan]

Summary

On AIX, the default arch level should match the minimum supported arch level of the OS version.

[jsji]

LGTM. Thanks.

clang/lib/Driver/ToolChains/CommonArgs.cpp

405

Please add comments here about AIX 7.2's minimal arch is P7.

[jsji]

clang/lib/Driver/ToolChains/CommonArgs.cpp

405

major == 7 should this be major <= 7 ? Or else, we may get pwr7 for AIX 5.1.

[stevewan]

clang/lib/Driver/ToolChains/CommonArgs.cpp

405

That's a great idea. Although I think we'd need to change major == 7 && minor < 2 to major < 7 || minor < 2 to also handle 4.3 and 5.3 properly. Let me know if you have further comments.

[jsji]

clang/lib/Driver/ToolChains/CommonArgs.cpp

403

micro unsed.

405

major < 7 || minor < 2 will have problem with AIX 8.1 later if we have AIX 8.

Maybe it is better to use
(major < 7 || (major == 7 && minor < 2))? "pwr4": "pwr7"

[stevewan]

Address comments with regard to handling older AIX versions.

[stevewan]

Improve handling different AIX versions.

[stevewan]

clang/lib/Driver/ToolChains/CommonArgs.cpp

403

Sorry I missed this comment. I agree that the unused micro is a bit ugly, do you have a preference on how you'd like it to be improved? We don't have an existing query for only major and minor, and creating one seems unnecessary IMHO. If you think renaming the variable to unused_micro mitigates the problem, I can do that.

[jsji]

clang/lib/Driver/ToolChains/CommonArgs.cpp

403

That's ok to me

[stevewan]

Reflect varible is unused in its name.

clang/lib/Driver/ToolChains/CommonArgs.cpp

std::string tools::getCPUName(const ArgList &Args, const llvm::Triple &T,
   case llvm::Triple::ppc64le: {
     std::string TargetCPUName = ppc::getPPCTargetCPU(Args);
     // LLVM may default to generating code for the native CPU,
     // but, like gcc, we default to a more generic option for
     // each architecture. (except on AIX)
     if (!TargetCPUName.empty())
       return TargetCPUName;
 
-    if (T.isOSAIX())
-      TargetCPUName = "pwr4";
-    else if (T.getArch() == llvm::Triple::ppc64le)
+    if (T.isOSAIX()) {
+      unsigned major, minor, unused_micro;
+      T.getOSVersion(major, minor, unused_micro);
+      // The minimal arch level moved from pwr4 for AIX7.1 to
+      // pwr7 for AIX7.2.
+      TargetCPUName =
+          (major < 7 || (major == 7 && minor < 2)) ? "pwr4" : "pwr7";
+    } else if (T.getArch() == llvm::Triple::ppc64le)
       TargetCPUName = "ppc64le";
     else if (T.getArch() == llvm::Triple::ppc64)
       TargetCPUName = "ppc64";
     else
       TargetCPUName = "ppc";
 
     return TargetCPUName;
   }

clang/test/Driver/aix-mcpu-default.c

-// Check that the target cpu defaults to power4 on AIX.
+// Check that the target cpu defaults to power7 on AIX7.2 and up.
 // RUN: %clang -no-canonical-prefixes %s -### -c 2>&1 \
-// RUN:        -target powerpc-ibm-aix \
-// RUN:   | FileCheck --check-prefix=CHECK-MCPU-DEFAULT %s
-// CHECK-MCPU-DEFAULT-NOT: warning:
-// CHECK-MCPU-DEFAULT:     {{.*}}clang{{.*}}" "-cc1"
-// CHECK-MCPU-DEFAULT:     "-target-cpu" "pwr4"
+// RUN:        -target powerpc-ibm-aix7.2 \
+// RUN:   | FileCheck --check-prefix=CHECK-MCPU-DEFAULT-AIX72 %s
+// CHECK-MCPU-DEFAULT-AIX72-NOT: warning:
+// CHECK-MCPU-DEFAULT-AIX72:     {{.*}}clang{{.*}}" "-cc1"
+// CHECK-MCPU-DEFAULT-AIX72:     "-target-cpu" "pwr7"
+
+// Check that the target cpu defaults to power4 on AIX7.1 and below.
+// RUN: %clang -no-canonical-prefixes %s -### -c 2>&1 \
+// RUN:        -target powerpc-ibm-aix7.1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MCPU-DEFAULT-AIX71 %s
+// CHECK-MCPU-DEFAULT-AIX71-NOT: warning:
+// CHECK-MCPU-DEFAULT-AIX71:     {{.*}}clang{{.*}}" "-cc1"
+// CHECK-MCPU-DEFAULT-AIX71:     "-target-cpu" "pwr4"
 
 // Check that the user is able to overwrite the default with '-mcpu'.
 // RUN: %clang -no-canonical-prefixes %s -### -c 2>&1 \
 // RUN:        -mcpu=pwr6 \
 // RUN:        -target powerpc-ibm-aix \
 // RUN:   | FileCheck --check-prefix=CHECK-MCPU-USER %s
 // CHECK-MCPU-USER-NOT: warning:
 // CHECK-MCPU-USER:     {{.*}}clang{{.*}}" "-cc1"
 // CHECK-MCPU-USER:     "-target-cpu" "pwr6"