[Support] Avoid normalization in sys::getDefaultTargetTriple

The return value of sys::getDefaultTargetTriple, which is derived from
-DLLVM_DEFAULT_TRIPLE, is used to construct tool names, default target,
and in the future also to control the search path directly; as such it
should be used textually, without interpretation by LLVM.

Normalization of this value may lead to unexpected results, for example
if we configure LLVM with -DLLVM_DEFAULT_TARGET_TRIPLE=x86_64-linux-gnu,
normalization will transform that value to x86_64--linux-gnu. Driver will
use that value to search for tools prefixed with x86_64--linux-gnu- which
may be confusing. This is also inconsistent with the behavior of the
--target flag which is taken as-is without any normalization and overrides
the value of LLVM_DEFAULT_TARGET_TRIPLE.

Users of sys::getDefaultTargetTriple already perform their own
normalization as needed, so this change shouldn't impact existing logic.

Differential Revision: https://reviews.llvm.org/D47153

llvm-svn: 333307

lib/Support/Unix/Host.inc

@@ -64,5 +64,5 @@ std::string sys::getDefaultTargetTriple() {
     TargetTripleString = EnvTriple;
 #endif
 
-  return Triple::normalize(TargetTripleString);
+  return TargetTripleString;
 }

lib/Support/Windows/Host.inc

@@ -30,5 +30,5 @@ std::string sys::getDefaultTargetTriple() {
     Triple = EnvTriple;
 #endif
 
-  return Triple::normalize(Triple);
+  return Triple;
 }