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InstCombine: Optimize GEP's involving ptrtoint better

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We supported transforming:
(gep i8* X, -(ptrtoint Y))

to:
(inttoptr (sub (ptrtoint X), (ptrtoint Y)))

However, this only fired if 'X' had type i8*.  Generalize this to
support various types of different sizes.  This results in much better
CodeGen, especially for pointers to packed structs.

llvm-svn: 216523
This commit is contained in:
David Majnemer 2014-08-27 05:16:04 +00:00
parent 4442146a4e
commit 826f5eb297
2 changed files with 74 additions and 11 deletions
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40
lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -1508,19 +1508,37 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
GetElementPtrInst::Create(Src->getOperand(0), Indices, GEP.getName()); GetElementPtrInst::Create(Src->getOperand(0), Indices, GEP.getName());
} }
// Canonicalize (gep i8* X, -(ptrtoint Y)) to (sub (ptrtoint X), (ptrtoint Y)) if (DL && GEP.getNumIndices() == 1) {
// The GEP pattern is emitted by the SCEV expander for certain kinds of
// pointer arithmetic.
if (DL && GEP.getNumIndices() == 1 &&
match(GEP.getOperand(1), m_Neg(m_PtrToInt(m_Value())))) {
unsigned AS = GEP.getPointerAddressSpace(); unsigned AS = GEP.getPointerAddressSpace();
if (GEP.getType() == Builder->getInt8PtrTy(AS) && if (GEP.getOperand(1)->getType()->getScalarSizeInBits() ==
GEP.getOperand(1)->getType()->getScalarSizeInBits() ==
DL->getPointerSizeInBits(AS)) { DL->getPointerSizeInBits(AS)) {
Operator *Index = cast<Operator>(GEP.getOperand(1)); Type *PtrTy = GEP.getPointerOperandType();
Value *PtrToInt = Builder->CreatePtrToInt(PtrOp, Index->getType()); Type *Ty = PtrTy->getPointerElementType();
Value *NewSub = Builder->CreateSub(PtrToInt, Index->getOperand(1)); uint64_t TyAllocSize = DL->getTypeAllocSize(Ty);
return CastInst::Create(Instruction::IntToPtr, NewSub, GEP.getType());
// Canonicalize (gep i8* X, -(ptrtoint Y)) to (sub (ptrtoint X), (ptrtoint Y))
// The GEP pattern is emitted by the SCEV expander for certain kinds of
// pointer arithmetic.
uint64_t C;
Value *NegPtrToInt = nullptr;
if (TyAllocSize == 1) {
NegPtrToInt = GEP.getOperand(1);
} else if (match(GEP.getOperand(1),
m_AShr(m_Value(NegPtrToInt), m_ConstantInt(C)))) {
if (TyAllocSize != 1ULL << C)
NegPtrToInt = nullptr;
} else if (match(GEP.getOperand(1),
m_SDiv(m_Value(NegPtrToInt), m_ConstantInt(C)))) {
if (TyAllocSize != C)
NegPtrToInt = nullptr;
}
if (NegPtrToInt && match(NegPtrToInt, m_Neg(m_PtrToInt(m_Value())))) {
Operator *Index = cast<Operator>(NegPtrToInt);
Value *PtrToInt = Builder->CreatePtrToInt(PtrOp, Index->getType());
Value *NewSub = Builder->CreateSub(PtrToInt, Index->getOperand(1));
return CastInst::Create(Instruction::IntToPtr, NewSub, GEP.getType());
}
} }
} }

45
test/Transforms/InstCombine/getelementptr.ll
View File

@ -6,6 +6,7 @@ target datalayout = "e-p:64:64-p1:16:16-p2:32:32:32-p3:64:64:64"
%pair = type { i32, i32 } %pair = type { i32, i32 }
%struct.B = type { double } %struct.B = type { double }
%struct.A = type { %struct.B, i32, i32 } %struct.A = type { %struct.B, i32, i32 }
%struct.C = type { [7 x i8] }
@Global = constant [10 x i8] c"helloworld" @Global = constant [10 x i8] c"helloworld"
@ -813,6 +814,50 @@ define i16 @test41([3 x i32] addrspace(1)* %array) {
; CHECK-NEXT: ret i16 8 ; CHECK-NEXT: ret i16 8
} }
define i8* @test42(i8* %c1, i8* %c2) {
%ptrtoint = ptrtoint i8* %c1 to i64
%sub = sub i64 0, %ptrtoint
%gep = getelementptr inbounds i8* %c2, i64 %sub
ret i8* %gep
; CHECK-LABEL: @test42(
; CHECK-NEXT: [[PTRTOINT1:%.*]] = ptrtoint i8* %c1 to i64
; CHECK-NEXT: [[PTRTOINT2:%.*]] = ptrtoint i8* %c2 to i64
; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[PTRTOINT2]], [[PTRTOINT1]]
; CHECK-NEXT: [[INTTOPTR:%.*]] = inttoptr i64 [[SUB]] to i8*
; CHECK-NEXT: ret i8* [[INTTOPTR]]
}
define i16* @test43(i16* %c1, i16* %c2) {
%ptrtoint = ptrtoint i16* %c1 to i64
%sub = sub i64 0, %ptrtoint
%shr = ashr i64 %sub, 1
%gep = getelementptr inbounds i16* %c2, i64 %shr
ret i16* %gep
; CHECK-LABEL: @test43(
; CHECK-NEXT: [[PTRTOINT1:%.*]] = ptrtoint i16* %c1 to i64
; CHECK-NEXT: [[PTRTOINT2:%.*]] = ptrtoint i16* %c2 to i64
; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[PTRTOINT2]], [[PTRTOINT1]]
; CHECK-NEXT: [[INTTOPTR:%.*]] = inttoptr i64 [[SUB]] to i16*
; CHECK-NEXT: ret i16* [[INTTOPTR]]
}
define %struct.C* @test44(%struct.C* %c1, %struct.C* %c2) {
%ptrtoint = ptrtoint %struct.C* %c1 to i64
%sub = sub i64 0, %ptrtoint
%shr = sdiv i64 %sub, 7
%gep = getelementptr inbounds %struct.C* %c2, i64 %shr
ret %struct.C* %gep
; CHECK-LABEL: @test44(
; CHECK-NEXT: [[PTRTOINT1:%.*]] = ptrtoint %struct.C* %c1 to i64
; CHECK-NEXT: [[PTRTOINT2:%.*]] = ptrtoint %struct.C* %c2 to i64
; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[PTRTOINT2]], [[PTRTOINT1]]
; CHECK-NEXT: [[INTTOPTR:%.*]] = inttoptr i64 [[SUB]] to %struct.C*
; CHECK-NEXT: ret %struct.C* [[INTTOPTR]]
}
define i32 addrspace(1)* @ascast_0_gep(i32* %p) nounwind { define i32 addrspace(1)* @ascast_0_gep(i32* %p) nounwind {
; CHECK-LABEL: @ascast_0_gep( ; CHECK-LABEL: @ascast_0_gep(
; CHECK-NOT: getelementptr ; CHECK-NOT: getelementptr