[PATCH] Add support for generating MIPS legacy NaN

[Vladimir Radosavljevic]

Hi dsanders, petarj,

Currently, the NaN values emitted for MIPS architectures, do not cover non-2008 compliant case. This change fixes the issue.

http://reviews.llvm.org/D7882

Files:
  include/clang/Basic/TargetInfo.h
  lib/AST/ExprConstant.cpp
  lib/Basic/Targets.cpp
  test/CodeGen/builtin-nan-legacy.c

Index: include/clang/Basic/TargetInfo.h
===================================================================
--- include/clang/Basic/TargetInfo.h
+++ include/clang/Basic/TargetInfo.h
@@ -638,6 +638,12 @@
     return std::string(1, *Constraint);
   }
 
+  /// \brief Returns true if NaN encoding is IEEE 754-2008.
+  /// Only on MIPS can be different encoding.
+  virtual bool isNan2008() const {
+    return true;
+  }
+
   /// \brief Returns a string of target-specific clobbers, in LLVM format.
   virtual const char *getClobbers() const = 0;
 
Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -7590,10 +7590,19 @@
   else if (S->getString().getAsInteger(0, fill))
     return false;
 
-  if (SNaN)
-    Result = llvm::APFloat::getSNaN(Sem, false, &fill);
-  else
-    Result = llvm::APFloat::getQNaN(Sem, false, &fill);
+  if (Context.getTargetInfo().isNan2008()) {
+    if (SNaN)
+      Result = llvm::APFloat::getSNaN(Sem, false, &fill);
+    else
+      Result = llvm::APFloat::getQNaN(Sem, false, &fill);
+  } else {
+    // This case will be triggered for Mips legacy encoding.
+    if (SNaN)
+      Result = llvm::APFloat::getQNaN(Sem, false, &fill);
+    else
+      Result = llvm::APFloat::getSNaN(Sem, false, &fill);
+  }
+
   return true;
 }
 
Index: lib/Basic/Targets.cpp
===================================================================
--- lib/Basic/Targets.cpp
+++ lib/Basic/Targets.cpp
@@ -5675,6 +5675,10 @@
     return CPU == "mips32r6" || ABI == "n32" || ABI == "n64" || ABI == "64";
   }
 
+  bool isNan2008() const override {
+    return IsNan2008 || isNaN2008Default();
+  }
+
   StringRef getABI() const override { return ABI; }
   bool setCPU(const std::string &Name) override {
     bool IsMips32 = getTriple().getArch() == llvm::Triple::mips ||
Index: test/CodeGen/builtin-nan-legacy.c
===================================================================
--- /dev/null
+++ test/CodeGen/builtin-nan-legacy.c
@@ -0,0 +1,13 @@
+// RUN: %clang -target mipsel-unknown-linux -mnan=legacy -emit-llvm -S -o %t %s
+// RUN: grep 'float 0x7FF4000000000000, float 0x7FF8000000000000' %t
+// RUN: grep 'double 0x7FF4000000000000, double 0x7FF8000000000000' %t
+
+float f[] = {
+  __builtin_nan(""),
+  __builtin_nans(""),
+};
+
+double d[] = {
+  __builtin_nan(""),
+  __builtin_nans(""),
+};

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