[X86] Make -march=i686 an alias of -march=pentiumpro

[craig.topper]

Summary

I think the only reason they are different is because we don't set tune_i686 for -march=i686 to match GCC. But GCC 4.9.0 seems to have changed this behavior and they do set it now. So I think they can aliases now.

[chandlerc]

LGTM, nice.

[craig.topper]

I suspect the gcc behavior changed when this bug was fixed https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59588

cfe/trunk/lib/Basic/Targets/X86.h

enum CPUKind {
     CK_i586,
     CK_Pentium,
     CK_PentiumMMX,
     //@}
 
     /// \name i686
     /// i686-generation processors, P6 / Pentium M microarchitecture based.
     //@{
-    CK_i686,
     CK_PentiumPro,
     CK_Pentium2,
     CK_Pentium3,
     CK_PentiumM,
     CK_C3_2,
 
     /// This enumerator is a bit odd, as GCC no longer accepts -march=yonah.
     /// Clang however has some logic to support this.

cfe/trunk/lib/Basic/Targets/X86.cpp

if (Kind != CK_Lakemont)
     setFeatureEnabledImpl(Features, "x87", true);
 
   switch (Kind) {
   case CK_Generic:
   case CK_i386:
   case CK_i486:
   case CK_i586:
   case CK_Pentium:
-  case CK_i686:
   case CK_PentiumPro:
   case CK_Lakemont:
     break;
 
   case CK_PentiumMMX:
   case CK_Pentium2:
   case CK_K6:
   case CK_WinChipC6:
void X86TargetInfo::getTargetDefines(const LangOptions &Opts,
   case CK_PentiumM:
     Builder.defineMacro("__tune_pentium3__");
     LLVM_FALLTHROUGH;
   case CK_Pentium2:
   case CK_C3_2:
     Builder.defineMacro("__tune_pentium2__");
     LLVM_FALLTHROUGH;
   case CK_PentiumPro:
-    Builder.defineMacro("__tune_i686__");
-    Builder.defineMacro("__tune_pentiumpro__");
-    LLVM_FALLTHROUGH;
-  case CK_i686:
-    Builder.defineMacro("__i686");
-    Builder.defineMacro("__i686__");
-    // Strangely, __tune_i686__ isn't defined by GCC when CPU == i686.
-    Builder.defineMacro("__pentiumpro");
-    Builder.defineMacro("__pentiumpro__");
+    defineCPUMacros(Builder, "i686");
+    defineCPUMacros(Builder, "pentiumpro");
     break;
   case CK_Pentium4:
     defineCPUMacros(Builder, "pentium4");
     break;
   case CK_Yonah:
   case CK_Prescott:
   case CK_Nocona:
     defineCPUMacros(Builder, "nocona");
bool X86TargetInfo::checkCPUKind(CPUKind Kind) const {
   case CK_i386:
   case CK_i486:
   case CK_WinChipC6:
   case CK_WinChip2:
   case CK_C3:
   case CK_i586:
   case CK_Pentium:
   case CK_PentiumMMX:
-  case CK_i686:
   case CK_PentiumPro:
   case CK_Pentium2:
   case CK_Pentium3:
   case CK_PentiumM:
   case CK_Yonah:
   case CK_C3_2:
   case CK_Pentium4:
   case CK_Lakemont:
return llvm::StringSwitch<CPUKind>(CPU)
       .Case("i386", CK_i386)
       .Case("i486", CK_i486)
       .Case("winchip-c6", CK_WinChipC6)
       .Case("winchip2", CK_WinChip2)
       .Case("c3", CK_C3)
       .Case("i586", CK_i586)
       .Case("pentium", CK_Pentium)
       .Case("pentium-mmx", CK_PentiumMMX)
-      .Case("i686", CK_i686)
-      .Case("pentiumpro", CK_PentiumPro)
+      .Cases("i686", "pentiumpro", CK_PentiumPro)
       .Case("pentium2", CK_Pentium2)
       .Cases("pentium3", "pentium3m", CK_Pentium3)
       .Case("pentium-m", CK_PentiumM)
       .Case("c3-2", CK_C3_2)
       .Case("yonah", CK_Yonah)
       .Cases("pentium4", "pentium4m", CK_Pentium4)
       .Case("prescott", CK_Prescott)
       .Case("nocona", CK_Nocona)

cfe/trunk/test/Preprocessor/predefined-arch-macros.c

 // RUN:     -target i386-unknown-linux \
 // RUN:   | FileCheck -match-full-lines %s -check-prefix=CHECK_I686_M32
 // CHECK_I686_M32: #define __i386 1
 // CHECK_I686_M32: #define __i386__ 1
 // CHECK_I686_M32: #define __i686 1
 // CHECK_I686_M32: #define __i686__ 1
 // CHECK_I686_M32: #define __pentiumpro 1
 // CHECK_I686_M32: #define __pentiumpro__ 1
+// CHECK_I686_M32: #define __tune_i686__ 1
+// CHECK_I686_M32: #define __tune_pentiumpro__ 1
 // CHECK_I686_M32: #define i386 1
 // RUN: not %clang -march=i686 -m64 -E -dM %s -o - 2>&1 \
 // RUN:     -target i386-unknown-linux \
 // RUN:   | FileCheck -match-full-lines %s -check-prefix=CHECK_I686_M64
 // CHECK_I686_M64: error: {{.*}}
 //
 // RUN: %clang -march=pentiumpro -m32 -E -dM %s -o - 2>&1 \
 // RUN:     -target i386-unknown-linux \