[LLVM-C] Add target triple normalization to the C API.

rL333307 was introduced to remove automatic target triple
normalization when calling sys::getDefaultTargetTriple(), arguing
that users of the latter already called Triple::normalize()
if necessary. However, users of the C API currently have no way of
doing target triple normalization.

This patch introduces an LLVMNormalizeTargetTriple function to
the C API which wraps Triple::normalize() and can be used on
the result of LLVMGetDefaultTargetTriple to achieve the same effect.

Differential Revision: https://reviews.llvm.org/D49414

Reviewed By: whitequark

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@337263 91177308-0d34-0410-b5e6-96231b3b80d8

Author: whitequark

include/llvm-c/TargetMachine.h

@@ -137,6 +137,10 @@ LLVMBool LLVMTargetMachineEmitToMemoryBuffer(LLVMTargetMachineRef T, LLVMModuleR
   disposed with LLVMDisposeMessage. */
 char* LLVMGetDefaultTargetTriple(void);
 
+/** Normalize a target triple. The result needs to be disposed with
+  LLVMDisposeMessage. */
+char* LLVMNormalizeTargetTriple(const char* triple);
+
 /** Get the host CPU as a string. The result needs to be disposed with
   LLVMDisposeMessage. */
 char* LLVMGetHostCPUName(void);

lib/Target/TargetMachineC.cpp

@@ -238,6 +238,10 @@ char *LLVMGetDefaultTargetTriple(void) {
   return strdup(sys::getDefaultTargetTriple().c_str());
 }
 
+char *LLVMNormalizeTargetTriple(const char* triple) {
+  return strdup(Triple::normalize(StringRef(triple)).c_str());
+}
+
 char *LLVMGetHostCPUName(void) {
   return strdup(sys::getHostCPUName().data());
 }