[Mips] Emit proper ABI for _mcount calls

When -pg option is present than a call to _mcount is inserted into every
function. However since the proper ABI was not followed then the generated
gmon.out did not give proper results. By inserting needed instructions 
before every _mcount we can fix this.

Differential Revision: https://reviews.llvm.org/D68390

llvm-svn: 374055

2 files changed, 49 insertions, 0 deletions

diff --git a/llvm/lib/Target/Mips/MipsSEISelDAGToDAG.cpp b/llvm/lib/Target/Mips/MipsSEISelDAGToDAG.cpp
index d9354cadc73..65afb3650f8 100644
--- a/llvm/lib/Target/Mips/MipsSEISelDAGToDAG.cpp
+++ b/llvm/lib/Target/Mips/MipsSEISelDAGToDAG.cpp
@@ -124,6 +124,33 @@ bool MipsSEDAGToDAGISel::replaceUsesWithZeroReg(MachineRegisterInfo *MRI,
   return true;
 }
 
+void MipsSEDAGToDAGISel::emitMCountABI(MachineInstr &MI, MachineBasicBlock &MBB,
+                                       MachineFunction &MF) {
+  MachineInstrBuilder MIB(MF, &MI);
+  if (!Subtarget->isABI_O32()) { // N32, N64
+    // Save current return address.
+    BuildMI(MBB, &MI, MI.getDebugLoc(), TII->get(Mips::OR))
+        .addDef(Mips::AT_64)
+        .addUse(Mips::RA_64)
+        .addUse(Mips::ZERO_64);
+    // Stops instruction above from being removed later on.
+    MIB.addUse(Mips::AT_64, RegState::Implicit);
+  } else {  // O32
+    // Save current return address.
+    BuildMI(MBB, &MI, MI.getDebugLoc(), TII->get(Mips::OR))
+        .addDef(Mips::AT)
+        .addUse(Mips::RA)
+        .addUse(Mips::ZERO);
+    // _mcount pops 2 words from stack.
+    BuildMI(MBB, &MI, MI.getDebugLoc(), TII->get(Mips::ADDiu))
+        .addDef(Mips::SP)
+        .addUse(Mips::SP)
+        .addImm(-8);
+    // Stops first instruction above from being removed later on.
+    MIB.addUse(Mips::AT, RegState::Implicit);
+  }
+}
+
 void MipsSEDAGToDAGISel::processFunctionAfterISel(MachineFunction &MF) {
   MF.getInfo<MipsFunctionInfo>()->initGlobalBaseReg();
 
@@ -150,6 +177,24 @@ void MipsSEDAGToDAGISel::processFunctionAfterISel(MachineFunction &MF) {
         if (Subtarget->isABI_FPXX() && !Subtarget->hasMTHC1())
           MI.addOperand(MachineOperand::CreateReg(Mips::SP, false, true));
         break;
+      case Mips::JAL:
+      case Mips::JAL_MM:
+        if (MI.getOperand(0).isGlobal() &&
+            MI.getOperand(0).getGlobal()->getGlobalIdentifier() == "_mcount")
+          emitMCountABI(MI, MBB, MF);
+        break;
+      case Mips::JALRPseudo:
+      case Mips::JALR64Pseudo:
+      case Mips::JALR16_MM:
+        if (MI.getOperand(2).isMCSymbol() &&
+            MI.getOperand(2).getMCSymbol()->getName() == "_mcount")
+          emitMCountABI(MI, MBB, MF);
+        break;
+      case Mips::JALR:
+        if (MI.getOperand(3).isMCSymbol() &&
+            MI.getOperand(3).getMCSymbol()->getName() == "_mcount")
+          emitMCountABI(MI, MBB, MF);
+        break;
       default:
         replaceUsesWithZeroReg(MRI, MI);
       }
diff --git a/llvm/lib/Target/Mips/MipsSEISelDAGToDAG.h b/llvm/lib/Target/Mips/MipsSEISelDAGToDAG.h
index 80ab1ea9f63..39f665be571 100644
--- a/llvm/lib/Target/Mips/MipsSEISelDAGToDAG.h
+++ b/llvm/lib/Target/Mips/MipsSEISelDAGToDAG.h
@@ -128,6 +128,10 @@ private:
 
   bool trySelect(SDNode *Node) override;
 
+  // Emits proper ABI for _mcount profiling calls.
+  void emitMCountABI(MachineInstr &MI, MachineBasicBlock &MBB,
+                     MachineFunction &MF);
+
   void processFunctionAfterISel(MachineFunction &MF) override;
 
   bool SelectInlineAsmMemoryOperand(const SDValue &Op,