[X86-64] Fix bugs in return type deduction analysis.

[Test] Add test from Issue 169.

X86/X86FuncPrototypeDiscovery.cpp

@@ -166,17 +166,6 @@ Type *X86MachineInstructionRaiser::getFunctionReturnType() {
     returnType = getReachingReturnType(*MBB);
   }
 
-  // If we are unable to discover the return type, check if return register is
-  // defined.
-  if (returnType == nullptr) {
-    for (MachineBasicBlock &MBB : MF) {
-      auto DiscoveredReturnType = getReachingReturnType(MBB);
-      if (DiscoveredReturnType != nullptr) {
-        returnType = DiscoveredReturnType;
-      }
-    }
-  }
-
   // If return type is still not discovered, assume it to be void
   if (returnType == nullptr)
     returnType = Type::getVoidTy(MF.getFunction().getContext());
@@ -561,12 +550,16 @@ Type *X86MachineInstructionRaiser::getReachingReturnType(
           BlockVisited.set(CurPredMBBNo);
           // Get function return type from MBB
           ReturnTypeOnPath = getReturnTypeFromMBB(*PredMBB, HasCall);
-          // Check out whether the ReturnType get from called instruction.
-          // Only keep the first find called function return type, continue
-          // to find other reach tree which has not call instruction.
-          // If the MBB has no call instruction and return type is not found,
-          // continue traversal up its predecessors.
+          // If PredMBB has no call and has no return  register definition,
+          // continue traversal.
           if (!HasCall && ReturnTypeOnPath == nullptr) {
+            // If PredMBB is the entry block and return type is not found, it
+            // implies that there is at least one path that doesn't set return
+            // register. Hence, there is no further need for further traversal.
+            if (PredMBB->isEntryBlock()) {
+              ReturnType = nullptr;
+              break;
+            }
             // Continue traversal
             for (auto Pred : PredMBB->predecessors()) {
               if (!BlockVisited[Pred->getNumber()])
@@ -631,11 +624,11 @@ X86MachineInstructionRaiser::getReturnTypeFromMBB(const MachineBasicBlock &MBB,
     if (I->isReturn())
       continue;
 
-    // No need to inspect padding instructions. ld uses nop and lld uses int3 for
-    // alignment padding in text section.
+    // No need to inspect padding instructions. ld uses nop and lld uses int3
+    // for alignment padding in text section.
     auto Opcode = I->getOpcode();
     if (isNoop(Opcode) || (Opcode == X86::INT3))
-    	continue;
+      continue;
 
     unsigned DefReg = X86::NoRegister;
     const TargetRegisterInfo *TRI = MF.getRegInfo().getTargetRegisterInfo();

X86/X86MachineInstructionRaiserUtils.cpp

@@ -251,7 +251,8 @@ Value *X86MachineInstructionRaiser::loadMemoryRefValue(
 bool X86MachineInstructionRaiser::deleteNOOPInstrMI(
     MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI) {
   MachineInstr &MI = *MBBI;
-  if (isNoop(MI.getOpcode())) {
+  auto Opcode = MI.getOpcode();
+  if (isNoop(Opcode) || Opcode == X86::INT3) {
     MBB.remove(&MI);
     return true;
   }
@@ -939,8 +940,9 @@ StoreInst *X86MachineInstructionRaiser::promotePhysregToStackSlot(
     StackLocTy = Type::getIntNTy(Ctxt, StackLocSzInBits);
   } else if (ReachingValue->getType()->isFloatingPointTy() ||
              ReachingValue->getType()->isVectorTy()) {
-    assert(StackLocSzInBits == 128 &&
-           "Expected FP types and vectors to be stored in 128 bit stack location");
+    assert(
+        StackLocSzInBits == 128 &&
+        "Expected FP types and vectors to be stored in 128 bit stack location");
     StackLocTy = VectorType::get(Type::getInt32Ty(Ctxt), 4, false);
   } else {
     llvm_unreachable("Unhandled type");

test/bug_fixes/issue169-1.c

@@ -0,0 +1,22 @@
+// REQUIRES: system-linux
+// RUN: clang -O3 -o %t %s
+// RUN: llvm-mctoll -d -I /usr/include/stdio.h %t
+// RUN: clang -o %t-dis %t-dis.ll
+// RUN: %t-dis 2>&1 | FileCheck %s
+// CHECK: 0000000000111111111122222222223333333333444444444455555555556666666666777777777788888888889999999999
+// CHECK-EMPTY
+
+#include <stdio.h>
+
+void foo() {
+    for(int i = 0; i < 10; i++) {
+        for (int j = 0; j < 10; j++) {
+            printf("%d", i);
+        }
+    }
+    printf("\n");
+}
+int main() {
+    foo();
+    return 0;
+}