[PPC64LE] Add -m[no-]optimize-swaps option

[wschmidt]

Summary

This patch adds a new switch (-m[no-]optimize-swaps) that sets the optimize-swaps feature attribute for the back end. The code controlled by this switch is under review at http://reviews.llvm.org/D8565.

[wschmidt]

In D8565, Eric questions this method of connecting an option for disabling a target pass with the back end. We do not currently have a better way of doing this. I'm ok with removing this, but see D8565 for further discussion.

[wschmidt]

Withdrawing this after discussion with interested parties. Using a cl::opt solution in llvm instead.

[echristo]

To be clear I wasn't objecting to the front end option necessarily, just the manner of communicating it to the backend. Perhaps the option should enable/disable the pass from running via the pass manager?

-eric

[wschmidt]

This is the method used by various other PowerPC passes, and was suggested by Hal. As I only want this for a chicken switch, using -mllvm <opt> is fine with me.

include/clang/Driver/Options.td

 def mmfcrf : Flag<["-"], "mmfcrf">, Group<m_ppc_Features_Group>;
 def mno_mfcrf : Flag<["-"], "mno-mfcrf">, Group<m_ppc_Features_Group>;
 def mpopcntd : Flag<["-"], "mpopcntd">, Group<m_ppc_Features_Group>;
 def mno_popcntd : Flag<["-"], "mno-popcntd">, Group<m_ppc_Features_Group>;
 def mqpx : Flag<["-"], "mqpx">, Group<m_ppc_Features_Group>;
 def mno_qpx : Flag<["-"], "mno-qpx">, Group<m_ppc_Features_Group>;
 def mcrbits : Flag<["-"], "mcrbits">, Group<m_ppc_Features_Group>;
 def mno_crbits : Flag<["-"], "mno-crbits">, Group<m_ppc_Features_Group>;
+def moptimize_swaps : Flag<["-"], "moptimize-swaps">,
+                      Group<m_ppc_Features_Group>;
+def mno_optimize_swaps : Flag<["-"], "mno-optimize-swaps">,
+                         Group<m_ppc_Features_Group>;
 def minvariant_function_descriptors :
   Flag<["-"], "minvariant-function-descriptors">, Group<m_ppc_Features_Group>;
 def mno_invariant_function_descriptors :
   Flag<["-"], "mno-invariant-function-descriptors">,
   Group<m_ppc_Features_Group>;
 
 def faltivec : Flag<["-"], "faltivec">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Enable AltiVec vector initializer syntax">;

test/Driver/ppc-features.cpp

 // CHECK-VSX: "-target-feature" "+vsx"
 
 // RUN: %clang -target powerpc64-unknown-linux-gnu %s -mno-power8-vector -### -o %t.o 2>&1 | FileCheck -check-prefix=CHECK-NOP8VECTOR %s
 // CHECK-NOP8VECTOR: "-target-feature" "-power8-vector"
 
 // RUN: %clang -target powerpc64-unknown-linux-gnu %s -mno-power8-vector -mpower8-vector -### -o %t.o 2>&1 | FileCheck -check-prefix=CHECK-P8VECTOR %s
 // CHECK-P8VECTOR: "-target-feature" "+power8-vector"
 
+// RUN: %clang -target powerpc64-unknown-linux-gnu %s -mno-optimize-swaps -### -o %t.o 2>&1 | FileCheck -check-prefix=CHECK-NOOPTSWAPS %s
+// CHECK-NOOPTSWAPS: "-target-feature" "-optimize-swaps"
+
+// RUN: %clang -target powerpc64-unknown-linux-gnu %s -mno-optimize-swaps -moptimize-swaps -### -o %t.o 2>&1 | FileCheck -check-prefix=CHECK-OPTSWAPS %s
+// CHECK-OPTSWAPS: "-target-feature" "+optimize-swaps"
+
 // RUN: %clang -target powerpc64-unknown-linux-gnu %s -mno-crbits -### -o %t.o 2>&1 | FileCheck -check-prefix=CHECK-NOCRBITS %s
 // CHECK-NOCRBITS: "-target-feature" "-crbits"
 
 // RUN: %clang -target powerpc64-unknown-linux-gnu %s -mno-crbits -mcrbits -### -o %t.o 2>&1 | FileCheck -check-prefix=CHECK-CRBITS %s
 // CHECK-CRBITS: "-target-feature" "+crbits"
 
 // RUN: %clang -target powerpc64-unknown-linux-gnu %s -mno-invariant-function-descriptors -### -o %t.o 2>&1 | FileCheck -check-prefix=CHECK-NOINVFUNCDESC %s
 // CHECK-NOINVFUNCDESC: "-target-feature" "-invariant-function-descriptors"