[Sparc][LEON] Detects an erratum on UT699 LEON 3 processors involving rounding mode changes and issues an appropriate user error message.

Differential Revision: https://reviews.llvm.org/D24665

llvm-svn: 284591

llvm/lib/Target/Sparc/LeonFeatures.td

@@ -66,6 +66,14 @@ def ReplaceFMULS : SubtargetFeature<
   "LEON erratum fix: Replace FMULS instruction with FMULD and relevant conversion instructions" 
 >;
 
+def DetectRoundChange : SubtargetFeature<
+  "detectroundchange",
+  "DetectRoundChange",
+  "true",
+  "LEON3 erratum detection: Detects any rounding mode change "
+  "request: use only the round-to-nearest rounding mode"
+>;
+
 def FixAllFDIVSQRT : SubtargetFeature<
   "fixallfdivsqrt",
   "FixAllFDIVSQRT",

llvm/lib/Target/Sparc/LeonPasses.cpp

@@ -16,6 +16,7 @@
 #include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
@@ -274,6 +275,50 @@ bool ReplaceFMULS::runOnMachineFunction(MachineFunction &MF) {
   return Modified;
 }
 
+
+//*****************************************************************************
+//**** DetectRoundChange pass
+//*****************************************************************************
+// To prevent any explicit change of the default rounding mode, this pass
+// detects any call of the fesetround function.
+// A warning is generated to ensure the user knows this has happened.
+//
+// Detects an erratum in UT699 LEON 3 processor
+
+char DetectRoundChange::ID = 0;
+
+DetectRoundChange::DetectRoundChange(TargetMachine &tm)
+    : LEONMachineFunctionPass(tm, ID) {}
+
+bool DetectRoundChange::runOnMachineFunction(MachineFunction &MF) {
+  Subtarget = &MF.getSubtarget<SparcSubtarget>();
+
+  bool Modified = false;
+  for (auto MFI = MF.begin(), E = MF.end(); MFI != E; ++MFI) {
+    MachineBasicBlock &MBB = *MFI;
+    for (auto MBBI = MBB.begin(), E = MBB.end(); MBBI != E; ++MBBI) {
+      MachineInstr &MI = *MBBI;
+      unsigned Opcode = MI.getOpcode();
+      if (Opcode == SP::CALL && MI.getNumOperands() > 0) {
+        MachineOperand &MO = MI.getOperand(0);
+
+        if (MO.isGlobal()) {
+          StringRef FuncName = MO.getGlobal()->getName();
+          if (FuncName.compare_lower("fesetround") == 0) {
+            errs() << "Error: You are using the detectroundchange "
+                      "option to detect rounding changes that will "
+                      "cause LEON errata. The only way to fix this "
+                      "is to remove the call to fesetround from "
+                      "the source code.\n";
+          }
+        }
+      }
+    }
+  }
+
+  return Modified;
+}
+
 //*****************************************************************************
 //**** FixAllFDIVSQRT pass
 //*****************************************************************************

llvm/lib/Target/Sparc/LeonPasses.h

@@ -84,6 +84,20 @@ public:
   }
 };
 
+class LLVM_LIBRARY_VISIBILITY DetectRoundChange
+    : public LEONMachineFunctionPass {
+public:
+  static char ID;
+
+  DetectRoundChange(TargetMachine &tm);
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  StringRef getPassName() const override {
+    return "DetectRoundChange: Leon erratum detection: detect any rounding "
+           "mode change request: use only the round-to-nearest rounding mode";
+  }
+};
+
 class LLVM_LIBRARY_VISIBILITY FixAllFDIVSQRT : public LEONMachineFunctionPass {
 public:
   static char ID;

llvm/lib/Target/Sparc/SparcSubtarget.cpp

@@ -44,6 +44,7 @@ SparcSubtarget &SparcSubtarget::initializeSubtargetDependencies(StringRef CPU,
   FixFSMULD = false;
   ReplaceFMULS = false;
   FixAllFDIVSQRT = false;
+  DetectRoundChange = false;
 
   // Determine default and user specified characteristics
   std::string CPUName = CPU;

llvm/lib/Target/Sparc/SparcSubtarget.h

@@ -48,6 +48,7 @@ class SparcSubtarget : public SparcGenSubtargetInfo {
   bool FixFSMULD;
   bool ReplaceFMULS;
   bool FixAllFDIVSQRT;
+  bool DetectRoundChange;
   bool PerformSDIVReplace;
 
   SparcInstrInfo InstrInfo;
@@ -93,6 +94,7 @@ public:
   bool fixFSMULD() const { return FixFSMULD; }
   bool replaceFMULS() const { return ReplaceFMULS; }
   bool fixAllFDIVSQRT() const { return FixAllFDIVSQRT; }
+  bool detectRoundChange() const { return DetectRoundChange; }
 
   /// ParseSubtargetFeatures - Parses features string setting specified
   /// subtarget options.  Definition of function is auto generated by tblgen.

llvm/lib/Target/Sparc/SparcTargetMachine.cpp

@@ -157,6 +157,9 @@ void SparcPassConfig::addPreEmitPass(){
   {
     addPass(new ReplaceFMULS(getSparcTargetMachine()));
   }
+  if (this->getSparcTargetMachine().getSubtargetImpl()->detectRoundChange()) {
+    addPass(new DetectRoundChange(getSparcTargetMachine()));
+  }
   if (this->getSparcTargetMachine().getSubtargetImpl()->fixAllFDIVSQRT())
   {
     addPass(new FixAllFDIVSQRT(getSparcTargetMachine()));

llvm/test/CodeGen/SPARC/LeonDetectRoundChangePassUT.ll

@@ -0,0 +1,22 @@
+; RUN: llc %s -O0 -march=sparc -mcpu=leon3 -mattr=+detectroundchange -o -  |& grep "detect rounding changes"
+
+; Function Attrs: nounwind
+declare i32 @fesetround(i32)
+
+define void @test_round_change() {
+entry:
+  %call = call i32 @fesetround(i32 2048)
+
+  ret void
+}
+; RUN: llc %s -O0 -march=sparc -mcpu=leon3 -mattr=+detectroundchange -o -  |& grep "detect rounding changes"
+
+; Function Attrs: nounwind
+declare i32 @fesetround(i32)
+
+define void @test_round_change() {
+entry:
+  %call = call i32 @fesetround(i32 2048)
+
+  ret void
+}