Hexagon: Add support to generate predicated absolute addressing mode

instructions.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174973 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Hexagon/HexagonInstrInfo.cpp

@@ -2237,38 +2237,141 @@ PredicateInstruction(MachineInstr *MI,
   assert (isPredicable(MI) && "Expected predicable instruction");
   bool invertJump = (!Cond.empty() && Cond[0].isImm() &&
                      (Cond[0].getImm() == 0));
-  MI->setDesc(get(getMatchingCondBranchOpcode(Opc, invertJump)));
-  //
-  // This assumes that the predicate is always the first operand
-  // in the set of inputs.
-  //
-  MI->addOperand(MI->getOperand(MI->getNumOperands()-1));
-  int oper;
-  for (oper = MI->getNumOperands() - 3; oper >= 0; --oper) {
-    MachineOperand MO = MI->getOperand(oper);
-    if ((MO.isReg() && !MO.isUse() && !MO.isImplicit())) {
-      break;
-    }
 
-    if (MO.isReg()) {
-      MI->getOperand(oper+1).ChangeToRegister(MO.getReg(), MO.isDef(),
-                                              MO.isImplicit(), MO.isKill(),
-                                              MO.isDead(), MO.isUndef(),
-                                              MO.isDebug());
-    } else if (MO.isImm()) {
-      MI->getOperand(oper+1).ChangeToImmediate(MO.getImm());
-    } else {
-      llvm_unreachable("Unexpected operand type");
+  // This will change MI's opcode to its predicate version.
+  // However, its operand list is still the old one, i.e. the
+  // non-predicate one.
+  MI->setDesc(get(getMatchingCondBranchOpcode(Opc, invertJump)));
+
+  int oper = -1;
+  unsigned int GAIdx = 0;
+
+  // Indicates whether the current MI has a GlobalAddress operand
+  bool hasGAOpnd = false;
+  std::vector<MachineOperand> tmpOpnds;
+
+  // Indicates whether we need to shift operands to right.
+  bool needShift = true;
+
+  // The predicate is ALWAYS the FIRST input operand !!!
+  if (MI->getNumOperands() == 0) {
+    // The non-predicate version of MI does not take any operands,
+    // i.e. no outs and no ins. In this condition, the predicate
+    // operand will be directly placed at Operands[0]. No operand
+    // shift is needed.
+    // Example: BARRIER
+    needShift = false;
+    oper = -1;
+  }
+  else if (   MI->getOperand(MI->getNumOperands()-1).isReg()
+           && MI->getOperand(MI->getNumOperands()-1).isDef()
+           && !MI->getOperand(MI->getNumOperands()-1).isImplicit()) {
+    // The non-predicate version of MI does not have any input operands.
+    // In this condition, we extend the length of Operands[] by one and
+    // copy the original last operand to the newly allocated slot.
+    // At this moment, it is just a place holder. Later, we will put
+    // predicate operand directly into it. No operand shift is needed.
+    // Example: r0=BARRIER (this is a faked insn used here for illustration)
+    MI->addOperand(MI->getOperand(MI->getNumOperands()-1));
+    needShift = false;
+    oper = MI->getNumOperands() - 2;
+  }
+  else {
+    // We need to right shift all input operands by one. Duplicate the
+    // last operand into the newly allocated slot.
+    MI->addOperand(MI->getOperand(MI->getNumOperands()-1));
+  }
+
+  if (needShift)
+  {
+    // Operands[ MI->getNumOperands() - 2 ] has been copied into
+    // Operands[ MI->getNumOperands() - 1 ], so we start from
+    // Operands[ MI->getNumOperands() - 3 ].
+    // oper is a signed int.
+    // It is ok if "MI->getNumOperands()-3" is -3, -2, or -1.
+    for (oper = MI->getNumOperands() - 3; oper >= 0; --oper)
+    {
+      MachineOperand &MO = MI->getOperand(oper);
+
+      // Opnd[0] Opnd[1] Opnd[2] Opnd[3] Opnd[4]   Opnd[5]   Opnd[6]   Opnd[7]
+      // <Def0>  <Def1>  <Use0>  <Use1>  <ImpDef0> <ImpDef1> <ImpUse0> <ImpUse1>
+      //               /\~
+      //              /||\~
+      //               ||
+      //        Predicate Operand here
+      if (MO.isReg() && !MO.isUse() && !MO.isImplicit()) {
+        break;
+      }
+      if (MO.isReg()) {
+        MI->getOperand(oper+1).ChangeToRegister(MO.getReg(), MO.isDef(),
+                                                MO.isImplicit(), MO.isKill(),
+                                                MO.isDead(), MO.isUndef(),
+                                                MO.isDebug());
+      }
+      else if (MO.isImm()) {
+        MI->getOperand(oper+1).ChangeToImmediate(MO.getImm());
+      }
+      else if (MO.isGlobal()) {
+        // MI can not have more than one GlobalAddress operand.
+        assert(hasGAOpnd == false && "MI can only have one GlobalAddress opnd");
+
+        // There is no member function called "ChangeToGlobalAddress" in the
+        // MachineOperand class (not like "ChangeToRegister" and
+        // "ChangeToImmediate"). So we have to remove them from Operands[] list
+        // first, and then add them back after we have inserted the predicate
+        // operand. tmpOpnds[] is to remember these operands before we remove
+        // them.
+        tmpOpnds.push_back(MO);
+
+        // Operands[oper] is a GlobalAddress operand;
+        // Operands[oper+1] has been copied into Operands[oper+2];
+        hasGAOpnd = true;
+        GAIdx = oper;
+        continue;
+      }
+      else {
+        assert(false && "Unexpected operand type");
+      }
     }
   }
 
   int regPos = invertJump ? 1 : 0;
   MachineOperand PredMO = Cond[regPos];
+
+  // [oper] now points to the last explicit Def. Predicate operand must be
+  // located at [oper+1]. See diagram above.
+  // This assumes that the predicate is always the first operand,
+  // i.e. Operands[0+numResults], in the set of inputs
+  // It is better to have an assert here to check this. But I don't know how
+  // to write this assert because findFirstPredOperandIdx() would return -1
+  if (oper < -1) oper = -1;
   MI->getOperand(oper+1).ChangeToRegister(PredMO.getReg(), PredMO.isDef(),
                                           PredMO.isImplicit(), PredMO.isKill(),
                                           PredMO.isDead(), PredMO.isUndef(),
                                           PredMO.isDebug());
 
+  if (hasGAOpnd)
+  {
+    unsigned int i;
+
+    // Operands[GAIdx] is the original GlobalAddress operand, which is
+    // already copied into tmpOpnds[0].
+    // Operands[GAIdx] now stores a copy of Operands[GAIdx-1]
+    // Operands[GAIdx+1] has already been copied into Operands[GAIdx+2],
+    // so we start from [GAIdx+2]
+    for (i = GAIdx + 2; i < MI->getNumOperands(); ++i)
+      tmpOpnds.push_back(MI->getOperand(i));
+
+    // Remove all operands in range [ (GAIdx+1) ... (MI->getNumOperands()-1) ]
+    // It is very important that we always remove from the end of Operands[]
+    // MI->getNumOperands() is at least 2 if program goes to here.
+    for (i = MI->getNumOperands() - 1; i > GAIdx; --i)
+      MI->RemoveOperand(i);
+
+    for (i = 0; i < tmpOpnds.size(); ++i)
+      MI->addOperand(tmpOpnds[i]);
+  }
+
   return true;
 }
 

test/CodeGen/Hexagon/pred-absolute-store.ll

@@ -0,0 +1,19 @@
+; RUN: llc -march=hexagon -mcpu=hexagonv4 < %s | FileCheck %s
+; Check that we are able to predicate instructions with abosolute
+; addressing mode.
+
+; CHECK: if{{ *}}(p{{[0-3]+}}){{ *}}memw(##gvar){{ *}}={{ *}}r{{[0-9]+}}
+
+@gvar = external global i32
+define i32 @test2(i32 %a, i32 %b) nounwind {
+entry:
+  %cmp = icmp eq i32 %a, %b
+  br i1 %cmp, label %if.then, label %if.end
+
+if.then:
+  store i32 %a, i32* @gvar, align 4
+  br label %if.end
+
+if.end:
+  ret i32 %b
+}