Improve asserts and restructure code flow.

Author: rj-jesus

llvm/lib/Target/AArch64/AArch64MIPeepholeOpt.cpp

@@ -164,6 +164,7 @@ INITIALIZE_PASS(AArch64MIPeepholeOpt, "aarch64-mi-peephole-opt",
 template <typename T>
 static bool splitBitmaskImm(T Imm, unsigned RegSize, T &Imm1Enc, T &Imm2Enc) {
   T UImm = static_cast<T>(Imm);
+  assert(UImm && (UImm != ~static_cast<T>(0)) && "Invalid immediate!");
 
   // The bitmask immediate consists of consecutive ones.  Let's say there is
   // constant 0b00000000001000000000010000000000 which does not consist of
@@ -194,6 +195,8 @@ static bool splitBitmaskImm(T Imm, unsigned RegSize, T &Imm1Enc, T &Imm2Enc) {
 template <typename T>
 static bool splitDisjointBitmaskImm(T Imm, unsigned RegSize, T &Imm1Enc,
                                     T &Imm2Enc) {
+  assert(Imm && (Imm != ~static_cast<T>(0)) && "Invalid immediate!");
+
   // Try to split a bitmask of the form 0b00000000011000000000011110000000 into
   // two disjoint masks such as 0b00000000011000000000000000000000 and
   // 0b00000000000000000000011110000000 where the inclusive/exclusive OR of the
@@ -207,17 +210,14 @@ static bool splitDisjointBitmaskImm(T Imm, unsigned RegSize, T &Imm1Enc,
               (static_cast<T>(1) << LowestBitSet);
   // Create a disjoint mask for the remaining ones.
   T NewImm2 = Imm & ~NewImm1;
-  assert(((NewImm1 & NewImm2) == 0) && "Non-disjoint immediates!");
-
-  if (AArch64_AM::isLogicalImmediate(NewImm2, RegSize)) {
-    assert(((NewImm1 | NewImm2) == Imm) && "Invalid immediates!");
-    assert(((NewImm1 ^ NewImm2) == Imm) && "Invalid immediates!");
-    Imm1Enc = AArch64_AM::encodeLogicalImmediate(NewImm1, RegSize);
-    Imm2Enc = AArch64_AM::encodeLogicalImmediate(NewImm2, RegSize);
-    return true;
-  }
 
-  return false;
+  // Do not split if NewImm2 is not a valid bitmask immediate.
+  if (!AArch64_AM::isLogicalImmediate(NewImm2, RegSize))
+    return false;
+
+  Imm1Enc = AArch64_AM::encodeLogicalImmediate(NewImm1, RegSize);
+  Imm2Enc = AArch64_AM::encodeLogicalImmediate(NewImm2, RegSize);
+  return true;
 }
 
 template <typename T>