Complete setting the baseline for ppc64le

[nemanjai]

Summary

As was uncovered by the failing test case (when run on non-PPC platforms), the feature set when compiling with -march=ppc64le was not being picked up. This change ensures that if the -mcpu option is not specified, the correct feature set is picked up regardless of whether we are on PPC or not.

[hfinkel]

LGTM.

[wschmidt]

Thanks, Hal. I will commit on Nemanja's behalf today.

[wschmidt]

Committed as r227455. Thanks, Nemanja!

lib/Target/PowerPC/PPCSubtarget.cpp

void PPCSubtarget::initializeEnvironment() {
   HasLazyResolverStubs = false;
   HasICBT = false;
   HasInvariantFunctionDescriptors = false;
 }
 
 void PPCSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
   // Determine default and user specified characteristics
   std::string CPUName = CPU;
-  if (CPUName.empty())
+  if (CPUName.empty()) {
+    // If cross-compiling with -march=ppc64le without -mcpu
+    if (TargetTriple.getArch() == Triple::ppc64le)
+      CPUName = "ppc64le";
+    else
       CPUName = "generic";
+  }
 #if (defined(__APPLE__) || defined(__linux__)) && \
     (defined(__ppc__) || defined(__powerpc__))
   if (CPUName == "generic")
     CPUName = sys::getHostCPUName();
 #endif
 
   // Initialize scheduling itinerary for the specified CPU.
   InstrItins = getInstrItineraryForCPU(CPUName);

test/CodeGen/PowerPC/ppc64le-aggregates.ll

 ; RUN: llc < %s -march=ppc64le -mcpu=pwr8 -mattr=+altivec -mattr=-vsx | FileCheck %s
+; RUN: llc < %s -march=ppc64le -mattr=+altivec -mattr=-vsx | FileCheck %s
 
 ; Currently VSX support is disabled for this test because we generate lxsdx
 ; instead of lfd, and stxsdx instead of stfd.  That is a poor choice when we
 ; have reg+imm addressing, and is on the list of things to be fixed.
+; The second run step is to ensure that -march=ppc64le is adequate to select
+; the same feature set as with -mcpu=pwr8 since that is the baseline for ppc64le.
 
 target datalayout = "e-m:e-i64:64-n32:64"
 target triple = "powerpc64le-unknown-linux-gnu"
 
 ;
 ; Verify use of registers for float/vector aggregate return.
 ;