From 9269d5c05bebe634dc9f08a37b192c6977fbc067 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Sat, 26 Jun 2010 23:03:20 +0000 Subject: [PATCH] Implement rdar://7530813 - collapse multiple GEP instructions in IRgen This avoids generating two gep's for common array operations. Before we would generate something like: %tmp = load i32* %X.addr ; [#uses=1] %arraydecay = getelementptr inbounds [100 x i32]* %A, i32 0, i32 0 ; [#uses=1] %arrayidx = getelementptr inbounds i32* %arraydecay, i32 %tmp ; [#uses=1] %tmp1 = load i32* %arrayidx ; [#uses=1] Now we generate: %tmp = load i32* %X.addr ; [#uses=1] %arrayidx = getelementptr inbounds [100 x i32]* %A, i32 0, i32 %tmp ; [#uses=1] %tmp1 = load i32* %arrayidx ; [#uses=1] Less IR is better at -O0. git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@106966 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/CGExpr.cpp | 45 +++++++++++++++++++++++++---- test/CodeGen/address-space-field2.c | 4 --- test/CodeGen/address-space-field3.c | 4 --- test/CodeGen/address-space-field4.c | 6 ---- test/CodeGen/exprs.c | 14 ++++++++- 5 files changed, 53 insertions(+), 20 deletions(-) diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp index 706bf09a7f..c41a99796d 100644 --- a/lib/CodeGen/CGExpr.cpp +++ b/lib/CodeGen/CGExpr.cpp @@ -1317,6 +1317,22 @@ llvm::BasicBlock *CodeGenFunction::getTrapBB() { return TrapBB; } +/// isSimpleArrayDecayOperand - If the specified expr is a simple decay from an +/// array to pointer, return the array subexpression. +static const Expr *isSimpleArrayDecayOperand(const Expr *E) { + // If this isn't just an array->pointer decay, bail out. + const CastExpr *CE = dyn_cast(E); + if (CE == 0 || CE->getCastKind() != CastExpr::CK_ArrayToPointerDecay) + return 0; + + // If this is a decay from variable width array, bail out. + const Expr *SubExpr = CE->getSubExpr(); + if (SubExpr->getType()->isVariableArrayType()) + return 0; + + return SubExpr; +} + LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E) { // The index must always be an integer, which is not an aggregate. Emit it. llvm::Value *Idx = EmitScalarExpr(E->getIdx()); @@ -1360,9 +1376,6 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E) { } } - // The base must be a pointer, which is not an aggregate. Emit it. - llvm::Value *Base = EmitScalarExpr(E->getBase()); - // We know that the pointer points to a type of the correct size, unless the // size is a VLA or Objective-C interface. llvm::Value *Address = 0; @@ -1378,9 +1391,13 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E) { Idx = Builder.CreateUDiv(Idx, llvm::ConstantInt::get(Idx->getType(), BaseTypeSize.getQuantity())); + + // The base must be a pointer, which is not an aggregate. Emit it. + llvm::Value *Base = EmitScalarExpr(E->getBase()); + Address = Builder.CreateInBoundsGEP(Base, Idx, "arrayidx"); - } else if (const ObjCObjectType *OIT = - E->getType()->getAs()) { + } else if (const ObjCObjectType *OIT = E->getType()->getAs()){ + // Indexing over an interface, as in "NSString *P; P[4];" llvm::Value *InterfaceSize = llvm::ConstantInt::get(Idx->getType(), getContext().getTypeSizeInChars(OIT).getQuantity()); @@ -1388,10 +1405,28 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E) { Idx = Builder.CreateMul(Idx, InterfaceSize); const llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(VMContext); + + // The base must be a pointer, which is not an aggregate. Emit it. + llvm::Value *Base = EmitScalarExpr(E->getBase()); Address = Builder.CreateGEP(Builder.CreateBitCast(Base, i8PTy), Idx, "arrayidx"); Address = Builder.CreateBitCast(Address, Base->getType()); + } else if (const Expr *Array = isSimpleArrayDecayOperand(E->getBase())) { + // If this is A[i] where A is an array, the frontend will have decayed the + // base to be a ArrayToPointerDecay implicit cast. While correct, it is + // inefficient at -O0 to emit a "gep A, 0, 0" when codegen'ing it, then a + // "gep x, i" here. Emit one "gep A, 0, i". + assert(Array->getType()->isArrayType() && + "Array to pointer decay must have array source type!"); + llvm::Value *ArrayPtr = EmitLValue(Array).getAddress(); + const llvm::Type *Int32Ty = llvm::Type::getInt32Ty(VMContext); + llvm::Value *Zero = llvm::ConstantInt::get(Int32Ty, 0); + llvm::Value *Args[] = { Zero, Idx }; + + Address = Builder.CreateInBoundsGEP(ArrayPtr, Args, Args+2, "arrayidx"); } else { + // The base must be a pointer, which is not an aggregate. Emit it. + llvm::Value *Base = EmitScalarExpr(E->getBase()); Address = Builder.CreateInBoundsGEP(Base, Idx, "arrayidx"); } diff --git a/test/CodeGen/address-space-field2.c b/test/CodeGen/address-space-field2.c index 198fd22a3a..9c21cab3a5 100644 --- a/test/CodeGen/address-space-field2.c +++ b/test/CodeGen/address-space-field2.c @@ -16,10 +16,6 @@ // CHECK: addrspace(1) // CHECK: addrspace(1) // CHECK: addrspace(1) -// CHECK: addrspace(1) -// CHECK: addrspace(1) -// CHECK: addrspace(2) -// CHECK: addrspace(2) // CHECK: addrspace(2) // CHECK: addrspace(2) // CHECK: addrspace(2) diff --git a/test/CodeGen/address-space-field3.c b/test/CodeGen/address-space-field3.c index 090f4a104b..c17085cdf4 100644 --- a/test/CodeGen/address-space-field3.c +++ b/test/CodeGen/address-space-field3.c @@ -16,10 +16,6 @@ // CHECK: addrspace(2) // CHECK: addrspace(2) // CHECK: addrspace(2) -// CHECK: addrspace(2) -// CHECK: addrspace(2) -// CHECK: addrspace(1) -// CHECK: addrspace(1) // CHECK: addrspace(1) // CHECK: addrspace(1) // CHECK: addrspace(1) diff --git a/test/CodeGen/address-space-field4.c b/test/CodeGen/address-space-field4.c index a1906c0c00..a896ab652d 100644 --- a/test/CodeGen/address-space-field4.c +++ b/test/CodeGen/address-space-field4.c @@ -23,9 +23,6 @@ // CHECK: addrspace(3) // CHECK: addrspace(3) // CHECK: addrspace(1) -// CHECK: addrspace(3) -// CHECK: addrspace(3) -// CHECK: addrspace(1) // CHECK: addrspace(1) // CHECK: addrspace(1) // CHECK: addrspace(1) @@ -35,9 +32,6 @@ // CHECK: addrspace(1) // CHECK: addrspace(1) // CHECK: addrspace(2) -// CHECK: addrspace(1) -// CHECK: addrspace(2) -// CHECK: addrspace(2) // CHECK: addrspace(2) // Check the load and store are using the correct address space to access diff --git a/test/CodeGen/exprs.c b/test/CodeGen/exprs.c index d182ce81ca..010e6e3cf5 100644 --- a/test/CodeGen/exprs.c +++ b/test/CodeGen/exprs.c @@ -1,4 +1,4 @@ -// RUN: %clang_cc1 %s -emit-llvm -o - +// RUN: %clang_cc1 %s -emit-llvm -o - | FileCheck %s // PR1895 // sizeof function @@ -119,3 +119,15 @@ void f9(struct S *x) { void f10() { __builtin_sin(0); } + +// rdar://7530813 +// CHECK: define i32 @f11 +int f11(long X) { + int A[100]; + return A[X]; + +// CHECK: load {{.*}}* %X.addr +// CHECK-NEXT: getelementptr inbounds [100 x i32]* %A, i32 0, +// CHECK-NEXT: load i32* +} + -- 2.40.0