From 9a7c0031de3ac332a5ca6b00b64c4cc4020620b4 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper@gmail.com>
Date: Tue, 31 Mar 2015 05:52:57 +0000
Subject: [PATCH] Make llc use getHostCPUFeatures when 'native' is specified
 for cpu.

This is necessary for x86 where not all Sandybridge, Ivybrige, Haswell, and Broadwell CPUs support AVX. Currently we modify the CPU name back to Nehalem for this case, but that turns off additional features for these CPUs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233673 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/MC/SubtargetFeature.h |  2 +-
 lib/MC/SubtargetFeature.cpp        |  5 +++--
 tools/llc/llc.cpp                  | 26 +++++++++++++++++++-------
 3 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/include/llvm/MC/SubtargetFeature.h b/include/llvm/MC/SubtargetFeature.h
index bfecb8ba6ab..6f195d7be99 100644
--- a/include/llvm/MC/SubtargetFeature.h
+++ b/include/llvm/MC/SubtargetFeature.h
@@ -78,7 +78,7 @@ public:
   std::string getString() const;
 
   /// Adding Features.
-  void AddFeature(StringRef String);
+  void AddFeature(StringRef String, bool Enable = true);
 
   /// ToggleFeature - Toggle a feature and returns the newly updated feature
   /// bits.
diff --git a/lib/MC/SubtargetFeature.cpp b/lib/MC/SubtargetFeature.cpp
index fcb43d63cb9..3880d883389 100644
--- a/lib/MC/SubtargetFeature.cpp
+++ b/lib/MC/SubtargetFeature.cpp
@@ -81,11 +81,12 @@ static std::string Join(const std::vector<std::string> &V) {
 }
 
 /// Adding features.
-void SubtargetFeatures::AddFeature(StringRef String) {
+void SubtargetFeatures::AddFeature(StringRef String, bool Enable) {
   // Don't add empty features.
   if (!String.empty())
     // Convert to lowercase, prepend flag if we don't already have a flag.
-    Features.push_back(hasFlag(String) ? String.lower() : "+" + String.lower());
+    Features.push_back(hasFlag(String) ? String.lower()
+                                       : (Enable ? "+" : "-") + String.lower());
 }
 
 /// Find KV in array using binary search.
diff --git a/tools/llc/llc.cpp b/tools/llc/llc.cpp
index 000948c10a0..d46cbb3181b 100644
--- a/tools/llc/llc.cpp
+++ b/tools/llc/llc.cpp
@@ -212,12 +212,6 @@ static int compileModule(char **argv, LLVMContext &Context) {
   bool SkipModule = MCPU == "help" ||
                     (!MAttrs.empty() && MAttrs.front() == "help");
 
-  // If user asked for the 'native' CPU, autodetect here. If autodection fails,
-  // this will set the CPU to an empty string which tells the target to
-  // pick a basic default.
-  if (MCPU == "native")
-    MCPU = sys::getHostCPUName();
-
   // If user just wants to list available options, skip module loading
   if (!SkipModule) {
     M = parseIRFile(InputFilename, Err, Context);
@@ -256,13 +250,31 @@ static int compileModule(char **argv, LLVMContext &Context) {
 
   // Package up features to be passed to target/subtarget
   std::string FeaturesStr;
-  if (MAttrs.size()) {
+  if (!MAttrs.empty() || MCPU == "native") {
     SubtargetFeatures Features;
+
+    // If user asked for the 'native' CPU, we need to autodetect features.
+    // This is necessary for x86 where the CPU might not support all the
+    // features the autodetected CPU name lists in the target. For example,
+    // not all Sandybridge processors support AVX.
+    if (MCPU == "native") {
+      StringMap<bool> HostFeatures;
+      if (sys::getHostCPUFeatures(HostFeatures))
+        for (auto &F : HostFeatures)
+          Features.AddFeature(F.first(), F.second);
+    }
+
     for (unsigned i = 0; i != MAttrs.size(); ++i)
       Features.AddFeature(MAttrs[i]);
     FeaturesStr = Features.getString();
   }
 
+  // If user asked for the 'native' CPU, autodetect here. If autodection fails,
+  // this will set the CPU to an empty string which tells the target to
+  // pick a basic default.
+  if (MCPU == "native")
+    MCPU = sys::getHostCPUName();
+
   CodeGenOpt::Level OLvl = CodeGenOpt::Default;
   switch (OptLevel) {
   default:
-- 
2.34.1