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Change getelementptr folding to use APInt instead of uint64_t for

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offset computations. This fixes a truncation bug on targets that
don't have 64-bit pointers.

llvm-svn: 79639
This commit is contained in:
Dan Gohman 2009-08-21 16:52:54 +00:00
parent 0da4ec0046
commit d240c19451
2 changed files with 34 additions and 14 deletions
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26
lib/Analysis/ConstantFolding.cpp
View File

@ -129,8 +129,9 @@ static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
Constant *Ptr = Ops[0];
if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized())
return 0;
uint64_t BasePtr = 0;
unsigned BitWidth = TD->getTypeSizeInBits(TD->getIntPtrType(Context));
APInt BasePtr(BitWidth, 0);
bool BaseIsInt = true;
if (!Ptr->isNullValue()) {
// If this is a inttoptr from a constant int, we can fold this as the base,
@ -138,7 +139,7 @@ static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
if (CE->getOpcode() == Instruction::IntToPtr)
if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0)))
BasePtr = Base->getZExtValue();
BasePtr = Base->getValue();
if (BasePtr == 0)
BaseIsInt = false;
@ -150,12 +151,13 @@ static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
if (!isa<ConstantInt>(Ops[i]))
return 0;
uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
(Value**)Ops+1, NumOps-1);
APInt Offset = APInt(BitWidth,
TD->getIndexedOffset(Ptr->getType(),
(Value**)Ops+1, NumOps-1));
// If the base value for this address is a literal integer value, fold the
// getelementptr to the resulting integer value casted to the pointer type.
if (BaseIsInt) {
Constant *C = ConstantInt::get(TD->getIntPtrType(Context), Offset+BasePtr);
Constant *C = ConstantInt::get(Context, Offset+BasePtr);
return ConstantExpr::getIntToPtr(C, ResultTy);
}
@ -171,19 +173,21 @@ static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
if (isa<PointerType>(ATy) && ATy != Ptr->getType())
break;
// Determine which element of the array the offset points into.
uint64_t ElemSize = TD->getTypeAllocSize(ATy->getElementType());
APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType()));
if (ElemSize == 0)
return 0;
uint64_t NewIdx = Offset / ElemSize;
APInt NewIdx = Offset.udiv(ElemSize);
Offset -= NewIdx * ElemSize;
NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Context), NewIdx));
Ty = ATy->getElementType();
} else if (const StructType *STy = dyn_cast<StructType>(Ty)) {
// Determine which field of the struct the offset points into.
// Determine which field of the struct the offset points into. The
// getZExtValue is at least as safe as the StructLayout API because we
// know the offset is within the struct at this point.
const StructLayout &SL = *TD->getStructLayout(STy);
unsigned ElIdx = SL.getElementContainingOffset(Offset);
unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue());
NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Context), ElIdx));
Offset -= SL.getElementOffset(ElIdx);
Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx));
Ty = STy->getTypeAtIndex(ElIdx);
} else {
// We've reached some non-indexable type.

22
test/Transforms/InstCombine/constant-fold-gep-overindex.ll
View File

@ -1,17 +1,33 @@
; RUN: llvm-as < %s | opt -instcombine
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | FileCheck %s
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 = "i386-apple-darwin10.0"
%0 = type { i8*, [19 x i8] }
%1 = type { i8*, [0 x i8] }
@array = external global [11 x i8]
@s = external global %0 ; <%0*> [#uses=1]
@"\01LC8" = external constant [17 x i8] ; <[17 x i8]*> [#uses=1]
; Instcombine should be able to fold this getelementptr.
define i32 @main() nounwind {
entry:
%0 = call i32 (i8*, ...)* @printf(i8* getelementptr ([17 x i8]* @"\01LC8", i32 0, i32 0), i8* undef, i8* getelementptr (%1* bitcast (%0* @s to %1*), i32 0, i32 1, i32 0)) nounwind ; <i32> [#uses=0]
; CHECK: call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([17 x i8]* @"\01LC8", i32 0, i32 0), i8* undef, i8* bitcast (i8** getelementptr (%1* bitcast (%0* @s to %1*), i32 1, i32 0) to i8*)) nounwind
call i32 (i8*, ...)* @printf(i8* getelementptr ([17 x i8]* @"\01LC8", i32 0, i32 0), i8* undef, i8* getelementptr (%1* bitcast (%0* @s to %1*), i32 0, i32 1, i32 0)) nounwind ; <i32> [#uses=0]
ret i32 0
}
; Instcombine should constant-fold the GEP so that indices that have
; static array extents are within bounds of those array extents.
; In the below, -1 is not in the range [0,11). After the transformation,
; the same address is computed, but 3 is in the range of [0,11).
define i8* @foo() nounwind {
; CHECK: ret i8* getelementptr ([11 x i8]* @array, i32 390451572, i32 3)
ret i8* getelementptr ([11 x i8]* @array, i32 0, i64 -1)
}
declare i32 @printf(i8*, ...) nounwind