[Power PC] llvm soft float support for ppc32

This is the second in a set of patches for soft float support for ppc32,
it enables soft float operations.

Patch by Strahinja Petrovic.

Differential Revision: http://reviews.llvm.org/D13700

llvm-svn: 255516

lib/Target/PowerPC/PPC.td

@@ -50,6 +50,8 @@ def DirectivePwr8: SubtargetFeature<"", "DarwinDirective", "PPC::DIR_PWR8", "">;
 
 def Feature64Bit     : SubtargetFeature<"64bit","Has64BitSupport", "true",
                                         "Enable 64-bit instructions">;
+def FeatureSoftFloat : SubtargetFeature<"soft-float", "UseSoftFloat", "true",
+                              "Use software emulation for floating point">;                                        
 def Feature64BitRegs : SubtargetFeature<"64bitregs","Use64BitRegs", "true",
                               "Enable 64-bit registers usage for ppc32 [beta]">;
 def FeatureCRBits    : SubtargetFeature<"crbits", "UseCRBits", "true",

lib/Target/PowerPC/PPCISelLowering.cpp

@@ -42,10 +42,6 @@
 
 using namespace llvm;
 
-// FIXME: Remove this once soft-float is supported.
-static cl::opt<bool> DisablePPCFloatInVariadic("disable-ppc-float-in-variadic",
-cl::desc("disable saving float registers for va_start on PPC"), cl::Hidden);
-
 static cl::opt<bool> DisablePPCPreinc("disable-ppc-preinc",
 cl::desc("disable preincrement load/store generation on PPC"), cl::Hidden);
 
@@ -72,8 +68,10 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM,
 
   // Set up the register classes.
   addRegisterClass(MVT::i32, &PPC::GPRCRegClass);
-  addRegisterClass(MVT::f32, &PPC::F4RCRegClass);
-  addRegisterClass(MVT::f64, &PPC::F8RCRegClass);
+  if (!Subtarget.useSoftFloat()) {
+    addRegisterClass(MVT::f32, &PPC::F4RCRegClass);
+    addRegisterClass(MVT::f64, &PPC::F8RCRegClass);
+  }
 
   // PowerPC has an i16 but no i8 (or i1) SEXTLOAD
   for (MVT VT : MVT::integer_valuetypes()) {
@@ -979,6 +977,10 @@ unsigned PPCTargetLowering::getByValTypeAlignment(Type *Ty,
   return Align;
 }
 
+bool PPCTargetLowering::useSoftFloat() const {
+  return Subtarget.useSoftFloat();
+}
+
 const char *PPCTargetLowering::getTargetNodeName(unsigned Opcode) const {
   switch ((PPCISD::NodeType)Opcode) {
   case PPCISD::FIRST_NUMBER:    break;
@@ -2945,8 +2947,9 @@ PPCTargetLowering::LowerFormalArguments_32SVR4(
       PPC::F8
     };
     unsigned NumFPArgRegs = array_lengthof(FPArgRegs);
-    if (DisablePPCFloatInVariadic)
-      NumFPArgRegs = 0;
+
+    if (Subtarget.useSoftFloat())
+       NumFPArgRegs = 0;
 
     FuncInfo->setVarArgsNumGPR(CCInfo.getFirstUnallocated(GPArgRegs));
     FuncInfo->setVarArgsNumFPR(CCInfo.getFirstUnallocated(FPArgRegs));

lib/Target/PowerPC/PPCISelLowering.h

@@ -428,6 +428,8 @@ namespace llvm {
     /// DAG node.
     const char *getTargetNodeName(unsigned Opcode) const override;
 
+    bool useSoftFloat() const override;
+
     MVT getScalarShiftAmountTy(const DataLayout &, EVT) const override {
       return MVT::i32;
     }

lib/Target/PowerPC/PPCSubtarget.cpp

@@ -62,6 +62,7 @@ void PPCSubtarget::initializeEnvironment() {
   Has64BitSupport = false;
   Use64BitRegs = false;
   UseCRBits = false;
+  UseSoftFloat = false;
   HasAltivec = false;
   HasSPE = false;
   HasQPX = false;

lib/Target/PowerPC/PPCSubtarget.h

@@ -83,6 +83,7 @@ protected:
   bool Has64BitSupport;
   bool Use64BitRegs;
   bool UseCRBits;
+  bool UseSoftFloat;
   bool IsPPC64;
   bool HasAltivec;
   bool HasSPE;
@@ -189,6 +190,8 @@ public:
   /// has64BitSupport - Return true if the selected CPU supports 64-bit
   /// instructions, regardless of whether we are in 32-bit or 64-bit mode.
   bool has64BitSupport() const { return Has64BitSupport; }
+  // useSoftFloat - Return true if soft-float option is turned on.
+  bool useSoftFloat() const { return UseSoftFloat; }
 
   /// use64BitRegs - Return true if in 64-bit mode or if we should use 64-bit
   /// registers in 32-bit mode when possible.  This can only true if

lib/Target/PowerPC/PPCTargetMachine.cpp

@@ -239,6 +239,19 @@ PPCTargetMachine::getSubtargetImpl(const Function &F) const {
                        ? FSAttr.getValueAsString().str()
                        : TargetFS;
 
+  // FIXME: This is related to the code below to reset the target options,
+  // we need to know whether or not the soft float flag is set on the
+  // function before we can generate a subtarget. We also need to use
+  // it as a key for the subtarget since that can be the only difference
+  // between two functions.
+  bool SoftFloat =
+    F.hasFnAttribute("use-soft-float") &&
+    F.getFnAttribute("use-soft-float").getValueAsString() == "true";
+  // If the soft float attribute is set on the function turn on the soft float
+  // subtarget feature.
+  if (SoftFloat)
+    FS += FS.empty() ? "+soft-float" : ",+soft-float";
+
   auto &I = SubtargetMap[CPU + FS];
   if (!I) {
     // This needs to be done before we create a new subtarget since any

test/CodeGen/PowerPC/ppcsoftops.ll

@@ -0,0 +1,50 @@
+; RUN: llc  -mtriple=powerpc-unknown-linux-gnu -O0 < %s | FileCheck %s
+define double @foo() #0 {
+entry:
+  %a = alloca double, align 8
+  %b = alloca double, align 8
+  %0 = load double, double* %a, align 8
+  %1 = load double, double* %b, align 8
+  %add = fadd double %0, %1
+  ret double %add
+
+  ; CHECK-LABEL:      __adddf3
+}
+
+define double @foo1() #0 {
+entry:
+  %a = alloca double, align 8
+  %b = alloca double, align 8
+  %0 = load double, double* %a, align 8
+  %1 = load double, double* %b, align 8
+  %mul = fmul double %0, %1
+  ret double %mul
+
+  ; CHECK-LABEL:      __muldf3
+}
+
+define double @foo2() #0 {
+entry:
+  %a = alloca double, align 8
+  %b = alloca double, align 8
+  %0 = load double, double* %a, align 8
+  %1 = load double, double* %b, align 8
+  %sub = fsub double %0, %1
+  ret double %sub
+
+  ; CHECK-LABEL:      __subdf3
+}
+
+define double @foo3() #0 {
+entry:
+  %a = alloca double, align 8
+  %b = alloca double, align 8
+  %0 = load double, double* %a, align 8
+  %1 = load double, double* %b, align 8
+  %div = fdiv double %0, %1
+  ret double %div
+
+  ; CHECK-LABEL:      __divdf3
+}
+
+attributes #0 = {"use-soft-float"="true" }