[ARM] Add support for target("arm") and target("thumb").

Summary:
This patch adds support for the target("arm") and target("thumb")
attributes, which can be used to force the compiler to generated ARM or
Thumb code for a function.

In LLVM, ARM or Thumb code generation can be controlled by the
thumb-mode target feature. But GCC already uses target("arm") and
target("thumb"), so we have to substitute "arm" with -thumb-mode and
"thumb" with +thumb-mode.


Reviewers: echristo, pcc, kristof.beyls

Reviewed By: echristo

Subscribers: ahatanak, aemerson, javed.absar, kristof.beyls, cfe-commits

Differential Revision: https://reviews.llvm.org/D33721

llvm-svn: 304781

1 files changed, 11 insertions, 1 deletions

diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp
index 605f73802af..bb8d81858ad 100644
--- a/clang/lib/Basic/Targets.cpp
+++ b/clang/lib/Basic/Targets.cpp
@@ -5438,7 +5438,17 @@ public:
       if (Feature[0] == '+')
         Features[Feature.drop_front(1)] = true;
 
-    return TargetInfo::initFeatureMap(Features, Diags, CPU, FeaturesVec);
+    // Convert user-provided arm and thumb GNU target attributes to
+    // [-|+]thumb-mode target features respectively.
+    std::vector<std::string> UpdatedFeaturesVec(FeaturesVec);
+    for (auto &Feature : UpdatedFeaturesVec) {
+      if (Feature.compare("+arm") == 0)
+        Feature = "-thumb-mode";
+      else if (Feature.compare("+thumb") == 0)
+        Feature = "+thumb-mode";
+    }
+
+    return TargetInfo::initFeatureMap(Features, Diags, CPU, UpdatedFeaturesVec);
   }
 
   bool handleTargetFeatures(std::vector<std::string> &Features,