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Constant-fold ptrtoint+add+inttoptr to gep when the pointer is an

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array and the add is within range. This helps simplify expressions
expanded by ScalarEvolutionExpander.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71158 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-05-07 14:24:56 +00:00
parent ecb403a9d3
commit 704b6980b8
2 changed files with 54 additions and 4 deletions
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40
lib/Analysis/ConstantFolding.cpp
View File

@ -16,6 +16,7 @@
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Instructions.h"
#include "llvm/Intrinsics.h"
#include "llvm/ADT/SmallVector.h"
@ -383,12 +384,43 @@ Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
// the int size is >= the ptr size. This requires knowing the width of a
// pointer, so it can't be done in ConstantExpr::getCast.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
if (TD && CE->getOpcode() == Instruction::PtrToInt &&
if (TD &&
TD->getPointerSizeInBits() <=
CE->getType()->getPrimitiveSizeInBits()) {
Constant *Input = CE->getOperand(0);
Constant *C = FoldBitCast(Input, DestTy, *TD);
return C ? C : ConstantExpr::getBitCast(Input, DestTy);
if (CE->getOpcode() == Instruction::PtrToInt) {
Constant *Input = CE->getOperand(0);
Constant *C = FoldBitCast(Input, DestTy, *TD);
return C ? C : ConstantExpr::getBitCast(Input, DestTy);
}
// If there's a constant offset added to the integer value before
// it is casted back to a pointer, see if the expression can be
// converted into a GEP.
if (CE->getOpcode() == Instruction::Add)
if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0)))
if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1)))
if (R->getOpcode() == Instruction::PtrToInt)
if (GlobalVariable *GV =
dyn_cast<GlobalVariable>(R->getOperand(0))) {
const PointerType *GVTy = cast<PointerType>(GV->getType());
if (const ArrayType *AT =
dyn_cast<ArrayType>(GVTy->getElementType())) {
const Type *ElTy = AT->getElementType();
uint64_t PaddedSize = TD->getTypePaddedSize(ElTy);
APInt PSA(L->getValue().getBitWidth(), PaddedSize);
if (ElTy == cast<PointerType>(DestTy)->getElementType() &&
L->getValue().urem(PSA) == 0) {
APInt ElemIdx = L->getValue().udiv(PSA);
if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(),
AT->getNumElements()))) {
Constant *Index[] = {
Constant::getNullValue(CE->getType()),
ConstantInt::get(ElemIdx)
};
return ConstantExpr::getGetElementPtr(GV, &Index[0], 2);
}
}
}
}
}
}
return ConstantExpr::getCast(Opcode, Ops[0], DestTy);

18
test/Transforms/InstCombine/constant-fold-ptr-casts.ll Normal file
View File

@ -0,0 +1,18 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {ret i32 2143034560}
; Instcombine should be able to completely fold this code.
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "i686-apple-darwin8"
@bar = constant [3 x i64] [i64 9220983451228067448, i64 9220983451228067449, i64 9220983450959631991], align 8
define i32 @foo() nounwind {
entry:
%tmp87.2 = load i64* inttoptr (i32 add (i32 16, i32 ptrtoint ([3 x i64]* @bar to i32)) to i64*), align 8
%t0 = bitcast i64 %tmp87.2 to double
%tmp9192.2 = fptrunc double %t0 to float
%t1 = bitcast float %tmp9192.2 to i32
ret i32 %t1
}