Pass target triple string in to TargetMachine constructor.

This is not just a matter of passing in the target triple from the module;
currently backends are making decisions based on the build and host
architecture. The goal is to migrate to making these decisions based off of the
triple (in conjunction with the feature string). Thus most clients pass in the
target triple, or the host triple if that is empty.

This has one important change in the way behavior of the JIT and llc.

For the JIT, it was previously selecting the Target based on the host
(naturally), but it was setting the target machine features based on the triple
from the module. Now it is setting the target machine features based on the
triple of the host.

For LLC, -march was previously only used to select the target, the target
machine features were initialized from the module's triple (which may have been
empty). Now the target triple is taken from the module, or the host's triple is
used if that is empty. Then the triple is adjusted to match -march.

The take away is that -march for llc is now used in conjunction with the host
triple to initialize the subtarget. If users want more deterministic behavior
from llc, they should use -mtriple, or set the triple in the input module.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77946 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 19 insertions, 9 deletions

diff --git a/tools/lto/LTOCodeGenerator.cpp b/tools/lto/LTOCodeGenerator.cpp
index a5023fb2f4..ac7af13cb8 100644
--- a/tools/lto/LTOCodeGenerator.cpp
+++ b/tools/lto/LTOCodeGenerator.cpp
@@ -35,6 +35,7 @@
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/StandardPasses.h"
 #include "llvm/Support/SystemUtils.h"
+#include "llvm/System/Host.h"
 #include "llvm/System/Signals.h"
 #include "llvm/Target/SubtargetFeature.h"
 #include "llvm/Target/TargetOptions.h"
@@ -326,11 +327,15 @@ bool LTOCodeGenerator::assemble(const std::string& asmPath,
 bool LTOCodeGenerator::determineTarget(std::string& errMsg)
 {
     if ( _target == NULL ) {
+        std::string Triple = _linker.getModule()->getTargetTriple();
+        if (Triple.empty())
+          Triple = sys::getHostTriple();
+
         // create target machine from info for merged modules
         Module* mergedModule = _linker.getModule();
         const Target *march = 
-          TargetRegistry::lookupTarget(mergedModule->getTargetTriple(), 
-                                       /*FallbackToHost=*/true,
+          TargetRegistry::lookupTarget(Triple,
+                                       /*FallbackToHost=*/false,
                                        /*RequireJIT=*/false,
                                        errMsg);
         if ( march == NULL )
@@ -351,9 +356,8 @@ bool LTOCodeGenerator::determineTarget(std::string& errMsg)
         }
 
         // construct LTModule, hand over ownership of module and target
-        std::string FeatureStr =
-          getFeatureString(_linker.getModule()->getTargetTriple().c_str());
-        _target = march->createTargetMachine(*mergedModule, FeatureStr.c_str());
+        std::string FeatureStr = getFeatureString(Triple.c_str());
+        _target = march->createTargetMachine(*mergedModule, Triple, FeatureStr);
     }
     return false;
 }
diff --git a/tools/lto/LTOModule.cpp b/tools/lto/LTOModule.cpp
index 4a2c5ad1dc..9a8b155275 100644
--- a/tools/lto/LTOModule.cpp
+++ b/tools/lto/LTOModule.cpp
@@ -24,6 +24,7 @@
 #include "llvm/Support/Mangler.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/MathExtras.h"
+#include "llvm/System/Host.h"
 #include "llvm/System/Path.h"
 #include "llvm/System/Process.h"
 #include "llvm/Target/SubtargetFeature.h"
@@ -149,17 +150,22 @@ LTOModule* LTOModule::makeLTOModule(MemoryBuffer* buffer,
     OwningPtr<Module> m(ParseBitcodeFile(buffer, getGlobalContext(), &errMsg));
     if ( !m )
         return NULL;
+
+    std::string Triple = m->getTargetTriple();
+    if (Triple.empty())
+      Triple = sys::getHostTriple();
+
     // find machine architecture for this module
-    const Target* march = TargetRegistry::lookupTarget(m->getTargetTriple(), 
-                                                       /*FallbackToHost=*/true,
+    const Target* march = TargetRegistry::lookupTarget(Triple, 
+                                                       /*FallbackToHost=*/false,
                                                        /*RequireJIT=*/false,
                                                        errMsg);
     if ( march == NULL ) 
         return NULL;
 
     // construct LTModule, hand over ownership of module and target
-    std::string FeatureStr = getFeatureString(m->getTargetTriple().c_str());
-    TargetMachine* target = march->createTargetMachine(*m, FeatureStr);
+    std::string FeatureStr = getFeatureString(Triple.c_str());
+    TargetMachine* target = march->createTargetMachine(*m, Triple, FeatureStr);
     return new LTOModule(m.take(), target);
 }