[ADT] Normalize empty triple components

LLVM triple normalization is handling "unknown" and empty components
differently; for example given "x86_64-unknown-linux-gnu" and
"x86_64-linux-gnu" which should be equivalent, triple normalization
returns "x86_64-unknown-linux-gnu" and "x86_64--linux-gnu". autoconf's
config.sub returns "x86_64-unknown-linux-gnu" for both
"x86_64-linux-gnu" and "x86_64-unknown-linux-gnu". This changes the
triple normalization to behave the same way, replacing empty triple
components with "unknown".

This addresses PR37129.

Differential Revision: https://reviews.llvm.org/D50219

llvm-svn: 339294

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Support/Triple.cpp b/llvm/lib/Support/Triple.cpp
index b14d6492b1e..c48be2d0cba 100644
--- a/llvm/lib/Support/Triple.cpp
+++ b/llvm/lib/Support/Triple.cpp
@@ -887,6 +887,12 @@ std::string Triple::normalize(StringRef Str) {
     }
   }
 
+  // Replace empty components with "unknown" value.
+  for (unsigned i = 0, e = Components.size(); i < e; ++i) {
+    if (Components[i].empty())
+      Components[i] = "unknown";
+  }
+
   // Special case logic goes here.  At this point Arch, Vendor and OS have the
   // correct values for the computed components.
   std::string NormalizedEnvironment;