Replace sequences of v.push_back(v[i]); v.erase(&v[i]); with std::rotate (NFC)

The code has a few sequence that looked like:

    Ops.push_back(Ops[0]);
    Ops.erase(Ops.begin());

And are equivalent to:

    std::rotate(Ops.begin(), Ops.begin() + 1, Ops.end());

The latter has the advantage of never reallocating the vector, which
would be a bug in the original code as push_back would read from the
memory it deallocated.

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 7f17a14..9cc58cf 100644 (file)
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -10748,8 +10748,7 @@ Value *CodeGenFunction::EmitAArch64BuiltinExpr(unsigned BuiltinID,
   case NEON::BI__builtin_neon_vld2q_lane_v: {
     llvm::Type *Tys[2] = { VTy, Ops[1]->getType() };
     Function *F = CGM.getIntrinsic(Intrinsic::aarch64_neon_ld2lane, Tys);
-    Ops.push_back(Ops[1]);
-    Ops.erase(Ops.begin()+1);
+    std::rotate(Ops.begin() + 1, Ops.begin() + 2, Ops.end());
     Ops[1] = Builder.CreateBitCast(Ops[1], Ty);
     Ops[2] = Builder.CreateBitCast(Ops[2], Ty);
     Ops[3] = Builder.CreateZExt(Ops[3], Int64Ty);
@@ -10762,8 +10761,7 @@ Value *CodeGenFunction::EmitAArch64BuiltinExpr(unsigned BuiltinID,
   case NEON::BI__builtin_neon_vld3q_lane_v: {
     llvm::Type *Tys[2] = { VTy, Ops[1]->getType() };
     Function *F = CGM.getIntrinsic(Intrinsic::aarch64_neon_ld3lane, Tys);
-    Ops.push_back(Ops[1]);
-    Ops.erase(Ops.begin()+1);
+    std::rotate(Ops.begin() + 1, Ops.begin() + 2, Ops.end());
     Ops[1] = Builder.CreateBitCast(Ops[1], Ty);
     Ops[2] = Builder.CreateBitCast(Ops[2], Ty);
     Ops[3] = Builder.CreateBitCast(Ops[3], Ty);
@@ -10777,8 +10775,7 @@ Value *CodeGenFunction::EmitAArch64BuiltinExpr(unsigned BuiltinID,
   case NEON::BI__builtin_neon_vld4q_lane_v: {
     llvm::Type *Tys[2] = { VTy, Ops[1]->getType() };
     Function *F = CGM.getIntrinsic(Intrinsic::aarch64_neon_ld4lane, Tys);
-    Ops.push_back(Ops[1]);
-    Ops.erase(Ops.begin()+1);
+    std::rotate(Ops.begin() + 1, Ops.begin() + 2, Ops.end());
     Ops[1] = Builder.CreateBitCast(Ops[1], Ty);
     Ops[2] = Builder.CreateBitCast(Ops[2], Ty);
     Ops[3] = Builder.CreateBitCast(Ops[3], Ty);
@@ -10791,16 +10788,14 @@ Value *CodeGenFunction::EmitAArch64BuiltinExpr(unsigned BuiltinID,
   }
   case NEON::BI__builtin_neon_vst2_v:
   case NEON::BI__builtin_neon_vst2q_v: {
-    Ops.push_back(Ops[0]);
-    Ops.erase(Ops.begin());
+    std::rotate(Ops.begin(), Ops.begin() + 1, Ops.end());
     llvm::Type *Tys[2] = { VTy, Ops[2]->getType() };
     return EmitNeonCall(CGM.getIntrinsic(Intrinsic::aarch64_neon_st2, Tys),
                         Ops, "");
   }
   case NEON::BI__builtin_neon_vst2_lane_v:
   case NEON::BI__builtin_neon_vst2q_lane_v: {
-    Ops.push_back(Ops[0]);
-    Ops.erase(Ops.begin());
+    std::rotate(Ops.begin(), Ops.begin() + 1, Ops.end());
     Ops[2] = Builder.CreateZExt(Ops[2], Int64Ty);
     llvm::Type *Tys[2] = { VTy, Ops[3]->getType() };
     return EmitNeonCall(CGM.getIntrinsic(Intrinsic::aarch64_neon_st2lane, Tys),
@@ -10808,16 +10803,14 @@ Value *CodeGenFunction::EmitAArch64BuiltinExpr(unsigned BuiltinID,
   }
   case NEON::BI__builtin_neon_vst3_v:
   case NEON::BI__builtin_neon_vst3q_v: {
-    Ops.push_back(Ops[0]);
-    Ops.erase(Ops.begin());
+    std::rotate(Ops.begin(), Ops.begin() + 1, Ops.end());
     llvm::Type *Tys[2] = { VTy, Ops[3]->getType() };
     return EmitNeonCall(CGM.getIntrinsic(Intrinsic::aarch64_neon_st3, Tys),
                         Ops, "");
   }
   case NEON::BI__builtin_neon_vst3_lane_v:
   case NEON::BI__builtin_neon_vst3q_lane_v: {
-    Ops.push_back(Ops[0]);
-    Ops.erase(Ops.begin());
+    std::rotate(Ops.begin(), Ops.begin() + 1, Ops.end());
     Ops[3] = Builder.CreateZExt(Ops[3], Int64Ty);
     llvm::Type *Tys[2] = { VTy, Ops[4]->getType() };
     return EmitNeonCall(CGM.getIntrinsic(Intrinsic::aarch64_neon_st3lane, Tys),
@@ -10825,16 +10818,14 @@ Value *CodeGenFunction::EmitAArch64BuiltinExpr(unsigned BuiltinID,
   }
   case NEON::BI__builtin_neon_vst4_v:
   case NEON::BI__builtin_neon_vst4q_v: {
-    Ops.push_back(Ops[0]);
-    Ops.erase(Ops.begin());
+    std::rotate(Ops.begin(), Ops.begin() + 1, Ops.end());
     llvm::Type *Tys[2] = { VTy, Ops[4]->getType() };
     return EmitNeonCall(CGM.getIntrinsic(Intrinsic::aarch64_neon_st4, Tys),
                         Ops, "");
   }
   case NEON::BI__builtin_neon_vst4_lane_v:
   case NEON::BI__builtin_neon_vst4q_lane_v: {
-    Ops.push_back(Ops[0]);
-    Ops.erase(Ops.begin());
+    std::rotate(Ops.begin(), Ops.begin() + 1, Ops.end());
     Ops[4] = Builder.CreateZExt(Ops[4], Int64Ty);
     llvm::Type *Tys[2] = { VTy, Ops[5]->getType() };
     return EmitNeonCall(CGM.getIntrinsic(Intrinsic::aarch64_neon_st4lane, Tys),