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Eliminate redundant bitwise operations when using a llvm/ADT/PointerUnion.
For comparison, with this code sample: PointerUnion<int *, char *> Data; PointerUnion<int *, char *> foo1() { Data = new int; return new int; } PointerUnion<int *, char *> foo2() { Data = new char; return new char; } Before this patch we would get: define i64 @_Z4foo1v() uwtable ssp { %1 = tail call noalias i8* @_Znwm(i64 4) %2 = ptrtoint i8* %1 to i64 %3 = load i64* getelementptr inbounds (%"class.llvm::PointerUnion"* @Data, i64 0, i32 0, i32 0), align 8 %4 = and i64 %3, 1 %.masked.i = and i64 %2, -3 %5 = or i64 %4, %.masked.i store i64 %5, i64* getelementptr inbounds (%"class.llvm::PointerUnion"* @Data, i64 0, i32 0, i32 0), align 8 %6 = tail call noalias i8* @_Znwm(i64 4) %7 = ptrtoint i8* %6 to i64 %8 = and i64 %7, -3 ret i64 %8 } define i64 @_Z4foo2v() uwtable ssp { %1 = tail call noalias i8* @_Znwm(i64 1) %2 = ptrtoint i8* %1 to i64 %3 = load i64* getelementptr inbounds (%"class.llvm::PointerUnion"* @Data, i64 0, i32 0, i32 0), align 8 %4 = and i64 %3, 1 %5 = or i64 %2, %4 %6 = or i64 %5, 2 store i64 %6, i64* getelementptr inbounds (%"class.llvm::PointerUnion"* @Data, i64 0, i32 0, i32 0), align 8 %7 = tail call noalias i8* @_Znwm(i64 1) %8 = ptrtoint i8* %7 to i64 %9 = or i64 %8, 2 ret i64 %9 } After the patch: define i64 @_Z4foo1v() uwtable ssp { %1 = tail call noalias i8* @_Znwm(i64 4) %2 = ptrtoint i8* %1 to i64 store i64 %2, i64* getelementptr inbounds (%"class.llvm::PointerUnion"* @Data, i64 0, i32 0, i32 0), align 8 %3 = tail call noalias i8* @_Znwm(i64 4) %4 = ptrtoint i8* %3 to i64 ret i64 %4 } declare noalias i8* @_Znwm(i64) define i64 @_Z4foo2v() uwtable ssp { %1 = tail call noalias i8* @_Znwm(i64 1) %2 = ptrtoint i8* %1 to i64 %3 = or i64 %2, 2 store i64 %3, i64* getelementptr inbounds (%"class.llvm::PointerUnion"* @Data, i64 0, i32 0, i32 0), align 8 %4 = tail call noalias i8* @_Znwm(i64 1) %5 = ptrtoint i8* %4 to i64 %6 = or i64 %5, 2 ret i64 %6 } git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169147 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -57,11 +57,13 @@ class PointerIntPair {
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};
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public:
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PointerIntPair() : Value(0) {}
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PointerIntPair(PointerTy Ptr, IntType Int) : Value(0) {
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PointerIntPair(PointerTy Ptr, IntType Int) {
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assert(IntBits <= PtrTraits::NumLowBitsAvailable &&
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"PointerIntPair formed with integer size too large for pointer");
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setPointer(Ptr);
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setInt(Int);
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setPointerAndInt(Ptr, Int);
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}
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explicit PointerIntPair(PointerTy Ptr) {
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initWithPointer(Ptr);
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}
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PointerTy getPointer() const {
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@ -91,6 +93,25 @@ public:
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Value |= IntVal << IntShift; // Set new integer.
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}
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void initWithPointer(PointerTy Ptr) {
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intptr_t PtrVal
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= reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(Ptr));
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assert((PtrVal & ((1 << PtrTraits::NumLowBitsAvailable)-1)) == 0 &&
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"Pointer is not sufficiently aligned");
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Value = PtrVal;
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}
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void setPointerAndInt(PointerTy Ptr, IntType Int) {
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intptr_t PtrVal
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= reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(Ptr));
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assert((PtrVal & ((1 << PtrTraits::NumLowBitsAvailable)-1)) == 0 &&
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"Pointer is not sufficiently aligned");
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intptr_t IntVal = Int;
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assert(IntVal < (1 << IntBits) && "Integer too large for field");
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Value = PtrVal | (IntVal << IntShift);
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}
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PointerTy const *getAddrOfPointer() const {
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return const_cast<PointerIntPair *>(this)->getAddrOfPointer();
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}
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@ -95,15 +95,11 @@ namespace llvm {
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public:
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PointerUnion() {}
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PointerUnion(PT1 V) {
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Val.setPointer(
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const_cast<void *>(PointerLikeTypeTraits<PT1>::getAsVoidPointer(V)));
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Val.setInt(0);
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PointerUnion(PT1 V) : Val(
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const_cast<void *>(PointerLikeTypeTraits<PT1>::getAsVoidPointer(V))) {
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}
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PointerUnion(PT2 V) {
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Val.setPointer(
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const_cast<void *>(PointerLikeTypeTraits<PT2>::getAsVoidPointer(V)));
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Val.setInt(1);
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PointerUnion(PT2 V) : Val(
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const_cast<void *>(PointerLikeTypeTraits<PT2>::getAsVoidPointer(V)), 1) {
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}
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/// isNull - Return true if the pointer held in the union is null,
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@ -160,15 +156,14 @@ namespace llvm {
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/// Assignment operators - Allow assigning into this union from either
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/// pointer type, setting the discriminator to remember what it came from.
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const PointerUnion &operator=(const PT1 &RHS) {
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Val.setPointer(
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Val.initWithPointer(
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const_cast<void *>(PointerLikeTypeTraits<PT1>::getAsVoidPointer(RHS)));
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Val.setInt(0);
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return *this;
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}
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const PointerUnion &operator=(const PT2 &RHS) {
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Val.setPointer(
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const_cast<void *>(PointerLikeTypeTraits<PT2>::getAsVoidPointer(RHS)));
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Val.setInt(1);
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Val.setPointerAndInt(
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const_cast<void *>(PointerLikeTypeTraits<PT2>::getAsVoidPointer(RHS)),
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1);
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return *this;
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}
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