From: Eli Friedman <eli.friedman@gmail.com>
Date: Sat, 2 Jul 2011 00:34:19 +0000 (+0000)
Subject: Make clang behave in a gcc-compatible way in the presence of multiple flags for the... 
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=d18eecac712bfbf63372cb78940d662ce9017840;p=clang

Make clang behave in a gcc-compatible way in the presence of multiple flags for the same x86 target feature (e.g. -mno-sse -msse).  gcc uses a somewhat unintuitive algorithm here in that the enabled SSE instructions is based on the order of the *last* flag for *each* feature-level, so that "-mno-sse -msse2" only enables SSE2, but "-mno-sse -msse2 -msse" enables all SSE levels.

Issue reported on cfe-dev.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@134296 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 78d8677a8a..8059fa9499 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -839,6 +839,14 @@ void Clang::AddX86TargetArgs(const ArgList &Args,
     CmdArgs.push_back(CPUName);
   }
 
+  // The required algorithm here is slightly strange: the options are applied
+  // in order (so -mno-sse -msse2 disables SSE3), but any option that gets
+  // directly overridden later is ignored (so "-mno-sse -msse2 -mno-sse2 -msse"
+  // is equivalent to "-mno-sse2 -msse"). The -cc1 handling deals with the
+  // former correctly, but not the latter; handle directly-overridden
+  // attributes here.
+  llvm::StringMap<unsigned> PrevFeature;
+  std::vector<const char*> Features;
   for (arg_iterator it = Args.filtered_begin(options::OPT_m_x86_Features_Group),
          ie = Args.filtered_end(); it != ie; ++it) {
     llvm::StringRef Name = (*it)->getOption().getName();
@@ -852,8 +860,17 @@ void Clang::AddX86TargetArgs(const ArgList &Args,
     if (IsNegative)
       Name = Name.substr(3);
 
-    CmdArgs.push_back("-target-feature");
-    CmdArgs.push_back(Args.MakeArgString((IsNegative ? "-" : "+") + Name));
+    unsigned& Prev = PrevFeature[Name];
+    if (Prev)
+      Features[Prev - 1] = 0;
+    Prev = Features.size() + 1;
+    Features.push_back(Args.MakeArgString((IsNegative ? "-" : "+") + Name));
+  }
+  for (unsigned i = 0; i < Features.size(); i++) {
+    if (Features[i]) {
+      CmdArgs.push_back("-target-feature");
+      CmdArgs.push_back(Features[i]);
+    }
   }
 }
 
diff --git a/test/Driver/x86_features.c b/test/Driver/x86_features.c
index 9dbdd0ae90..0db372ec64 100644
--- a/test/Driver/x86_features.c
+++ b/test/Driver/x86_features.c
@@ -1,3 +1,3 @@
 // RUN: %clang -ccc-host-triple i386-unknown-unknown -### -S %s -msse -msse4 -mno-sse -mno-mmx -msse 2> %t
-// RUN: grep '"-target-feature" "+sse" "-target-feature" "+sse4" "-target-feature" "-sse" "-target-feature" "-mmx" "-target-feature" "+sse"' %t
-
+// RUN: grep '"pentium4" "-target-feature" "+sse4" "-target-feature" "-mmx" "-target-feature" "+sse"' %t
+// Note that we filter out all but the last -m(no)sse.