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generalize the previous transformation to handle indexing into 

arrays of structs and other arrays, so long as all the subsequent
indexes are constants.  This triggers frequently for stuff like:

@divisions = internal constant [29 x [2 x i32]] [[2 x i32] zeroinitializer, [2 x i32] [i32 0, i32 1], [2 x i32] [i32 0, i32 2], [2 x i32] [i32 0, i32 1], [2 x i32] zeroinitializer, [2 x i32] [i32 0, i32 1], [2 x i32] [i32 0, i32 1], [2 x i32] [i32 0, i32 2], [2 x i32] [i32 0, i32 2], [2 x i32] zeroinitializer, [2 x i32] zeroinitializer, [2 x i32] zeroinitializer, [2 x i32] [i32 0, i32 2], [2 x i32] [i32 0, i32 1], [2 x i32] zeroinitializer, [2 x i32] [i32 1, i32 0], [2 x i32] [i32 1, i32 1], [2 x i32] [i32 1, i32 1], [2 x i32] [i32 1, i32 2], [2 x i32] [i32 1, i32 1], [2 x i32] [i32 1, i32 0], [2 x i32] [i32 1, i32 2], [2 x i32] [i32 1, i32 2], [2 x i32] [i32 1, i32 0], [2 x i32] [i32 1, i32 0], [2 x i32] [i32 1, i32 0], [2 x i32] [i32 1, i32 1], [2 x i32] [i32 1, i32 2], [2 x i32] [i32 1, i32 2]], align 32 ; <[29 x [2 x i32]]*> [#uses=50]

	  %623 = getelementptr inbounds [29 x [2 x i32]]* @divisions, i64 0, i64 %619, i64 0 ; <i32*> [#uses=1]
	   %684 = icmp eq i32 %683, 999 

also for the "my_defs" table in 'gs', etc.

llvm-svn: 92444
This commit is contained in:
Chris Lattner 2010-01-03 03:03:27 +00:00
parent c6f59b1c49
commit fca0c8f93a
2 changed files with 73 additions and 19 deletions
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74
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -6017,7 +6017,6 @@ Instruction *InstCombiner::FoldFCmp_IntToFP_Cst(FCmpInst &I,
return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt);
}
/// FoldCmpLoadFromIndexedGlobal - Called we see this pattern:
/// cmp pred (load (gep GV, ...)), cmpcst
/// where GV is a global variable with a constant initializer. Try to simplify
@ -6029,18 +6028,43 @@ Instruction *InstCombiner::FoldFCmp_IntToFP_Cst(FCmpInst &I,
Instruction *InstCombiner::
FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
CmpInst &ICI, ConstantInt *AndCst) {
ConstantArray *Init = dyn_cast<ConstantArray>(GV->getInitializer());
if (Init == 0 || Init->getNumOperands() > 1024) return 0;
// There are many forms of this optimization we can handle, for now, just do
// the simple index into a single-dimensional array.
//
// Require: GEP GV, 0, i
if (GEP->getNumOperands() != 3 ||
// Require: GEP GV, 0, i {{, constant indices}}
if (GEP->getNumOperands() < 3 ||
!isa<ConstantInt>(GEP->getOperand(1)) ||
!cast<ConstantInt>(GEP->getOperand(1))->isZero())
!cast<ConstantInt>(GEP->getOperand(1))->isZero() ||
isa<Constant>(GEP->getOperand(2)))
return 0;
// Check that indices after the variable are constants and in-range for the
// type they index. Collect the indices. This is typically for arrays of
// structs.
SmallVector<unsigned, 4> LaterIndices;
ConstantArray *Init = dyn_cast<ConstantArray>(GV->getInitializer());
if (Init == 0 || Init->getNumOperands() > 1024) return 0;
const Type *EltTy = cast<ArrayType>(Init->getType())->getElementType();
for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) {
ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i));
if (Idx == 0) return 0; // Variable index.
uint64_t IdxVal = Idx->getZExtValue();
if ((unsigned)IdxVal != IdxVal) return 0; // Too large array index.
if (const StructType *STy = dyn_cast<StructType>(EltTy))
EltTy = STy->getElementType(IdxVal);
else if (const ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) {
if (IdxVal >= ATy->getNumElements()) return 0;
EltTy = ATy->getElementType();
} else {
return 0; // Unknown type.
}
LaterIndices.push_back(IdxVal);
}
enum { Overdefined = -3, Undefined = -2 };
@ -6076,6 +6100,11 @@ FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
for (unsigned i = 0, e = Init->getNumOperands(); i != e; ++i) {
Constant *Elt = Init->getOperand(i);
// If this is indexing an array of structures, get the structure element.
if (!LaterIndices.empty())
Elt = ConstantExpr::getExtractValue(Elt, LaterIndices.data(),
LaterIndices.size());
// If the element is masked, handle it.
if (AndCst) Elt = ConstantExpr::getAnd(Elt, AndCst);
@ -6244,8 +6273,6 @@ FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0));
}
// TODO: GEP 0, i, 4
return 0;
}
@ -6337,12 +6364,15 @@ Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
!cast<LoadInst>(LHSI)->isVolatile())
!cast<LoadInst>(LHSI)->isVolatile()) {
if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV, I))
return Res;
//errs() << "NOT HANDLED FP: " << *GV << "\n";
//errs() << "\t" << *GEP << "\n";
//errs() << "\t " << I << "\n\n\n";
#if 0
errs() << "NOT HANDLED FP: " << *GV << "\n";
errs() << "\t" << *GEP << "\n";
errs() << "\t " << I << "\n\n\n";
#endif
}
}
break;
}
@ -6731,12 +6761,15 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
!cast<LoadInst>(LHSI)->isVolatile())
!cast<LoadInst>(LHSI)->isVolatile()) {
if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV, I))
return Res;
//errs() << "NOT HANDLED INT: " << *GV << "\n";
//errs() << "\t" << *GEP << "\n";
//errs() << "\t " << I << "\n\n\n";
#if 0
errs() << "NOT HANDLED INT: " << *GV << "\n";
errs() << "\t" << *GEP << "\n";
errs() << "\t " << I << "\n\n\n";
#endif
}
}
break;
}
@ -7401,9 +7434,12 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
ConstantInt *C = cast<ConstantInt>(LHSI->getOperand(1));
if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV,ICI, C))
return Res;
//errs() << "NOT HANDLED INT: " << *GV << "\n";
//errs() << "\t" << *GEP << "\n";
//errs() << "\t " << I << "\n\n\n";
#if 0
errs() << "NOT HANDLED 'AND': " << *GV << "\n";
errs() << "\t" << *GEP << "\n";
errs() << "\t " << *LHSI << "\n\n\n";
errs() << "\t " << ICI << "\n\n\n";
#endif
}
}
break;

18
llvm/test/Transforms/InstCombine/load-cmp.ll
View File

@ -92,3 +92,21 @@ define i1 @test8(i32 %X) {
; CHECK-NEXT: %S = icmp ult i32 {{.*}}, 2
; CHECK-NEXT: ret i1 %S
}
@GA = internal constant [4 x { i32, i32 } ] [
{ i32, i32 } { i32 1, i32 0 },
{ i32, i32 } { i32 2, i32 1 },
{ i32, i32 } { i32 3, i32 1 },
{ i32, i32 } { i32 4, i32 0 }
]
define i1 @test9(i32 %X) {
%P = getelementptr [4 x { i32, i32 } ]* @GA, i32 0, i32 %X, i32 1
%Q = load i32* %P
%R = icmp eq i32 %Q, 1
ret i1 %R
; CHECK: @test9
; CHECK-NEXT: add i32 %X, -1
; CHECK-NEXT: %R = icmp ult i32 {{.*}}, 2
; CHECK-NEXT: ret i1 %R
}