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"ret (constexpr)" can't be folded into a Constant. Add a method to

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Analysis/ConstantFolding to fold ConstantExpr's, then make instcombine use it
to try to use targetdata to fold constant expressions on void instructions.

Also extend the icmp(inttoptr, inttoptr) folding to handle the case where
int size != ptr size.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51559 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2008-05-25 20:56:15 +00:00
parent a5464f3659
commit 3dfd7bf511
4 changed files with 74 additions and 16 deletions
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6
include/llvm/Analysis/ConstantFolding.h
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@ -30,6 +30,12 @@ namespace llvm {
///
Constant *ConstantFoldInstruction(Instruction *I, const TargetData *TD = 0);
/// ConstantFoldConstantExpression - Attempt to fold the constant expression
/// using the specified TargetData. If successful, the constant result is
/// result is returned, if not, null is returned.
Constant *ConstantFoldConstantExpression(ConstantExpr *CE,
const TargetData *TD);
/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
/// specified operands. If successful, the constant result is returned, if not,
/// null is returned. Note that this function can fail when attempting to

61
lib/Analysis/ConstantFolding.cpp
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@ -312,6 +312,25 @@ Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) {
&Ops[0], Ops.size(), TD);
}
/// ConstantFoldConstantExpression - Attempt to fold the constant expression
/// using the specified TargetData. If successful, the constant result is
/// result is returned, if not, null is returned.
Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE,
const TargetData *TD) {
assert(TD && "ConstantFoldConstantExpression requires a valid TargetData.");
SmallVector<Constant*, 8> Ops;
for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i)
Ops.push_back(cast<Constant>(*i));
if (CE->isCompare())
return ConstantFoldCompareInstOperands(CE->getPredicate(),
&Ops[0], Ops.size(), TD);
else
return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
&Ops[0], Ops.size(), TD);
}
/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
/// specified opcode and operands. If successful, the constant result is
/// returned, if not, null is returned. Note that this function can fail when
@ -398,7 +417,7 @@ Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
const TargetData *TD) {
// fold: icmp (inttoptr x), null -> icmp x, 0
// fold: icmp (ptrtoint x), 0 -> icmp x, null
// fold: icmp (inttoptr x), (inttoptr y) -> icmp x, y
// fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
// fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
//
// ConstantExpr::getCompare cannot do this, because it doesn't have TD
@ -426,21 +445,31 @@ Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
}
}
if (TD && isa<ConstantExpr>(Ops[1]) &&
cast<ConstantExpr>(Ops[1])->getOpcode() == CE0->getOpcode()) {
const Type *IntPtrTy = TD->getIntPtrType();
// Only do this transformation if the int is intptrty in size, otherwise
// there is a truncation or extension that we aren't modeling.
if ((CE0->getOpcode() == Instruction::IntToPtr &&
CE0->getOperand(0)->getType() == IntPtrTy &&
Ops[1]->getOperand(0)->getType() == IntPtrTy) ||
(CE0->getOpcode() == Instruction::PtrToInt &&
CE0->getType() == IntPtrTy &&
CE0->getOperand(0)->getType() == Ops[1]->getOperand(0)->getType())) {
Constant *NewOps[] = {
CE0->getOperand(0), cast<ConstantExpr>(Ops[1])->getOperand(0)
};
return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops[1])) {
if (TD && CE0->getOpcode() == CE1->getOpcode()) {
const Type *IntPtrTy = TD->getIntPtrType();
if (CE0->getOpcode() == Instruction::IntToPtr) {
// Convert the integer value to the right size to ensure we get the
// proper extension or truncation.
Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
IntPtrTy, false);
Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
IntPtrTy, false);
Constant *NewOps[] = { C0, C1 };
return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
}
// Only do this transformation if the int is intptrty in size, otherwise
// there is a truncation or extension that we aren't modeling.
if ((CE0->getOpcode() == Instruction::PtrToInt &&
CE0->getType() == IntPtrTy &&
CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) {
Constant *NewOps[] = {
CE0->getOperand(0), CE1->getOperand(0)
};
return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
}
}
}
}

10
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -11887,6 +11887,16 @@ bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
continue;
}
if (TD && I->getType()->getTypeID() == Type::VoidTyID) {
// See if we can constant fold its operands.
for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) {
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(i)) {
if (Constant *NewC = ConstantFoldConstantExpression(CE, TD))
i->set(NewC);
}
}
}
// See if we can trivially sink this instruction to a successor basic block.
// FIXME: Remove GetResultInst test when first class support for aggregates
// is implemented.

13
test/Transforms/InstCombine/2008-05-18-FoldIntToPtr.ll Normal file
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@ -0,0 +1,13 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {ret i1 false} | count 2
; PR2329
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-f80:32:32"
target triple = "i386-pc-linux-gnu"
define i1 @f1() {
ret i1 icmp eq (i8* inttoptr (i32 1 to i8*), i8* inttoptr (i32 2 to i8*))
}
define i1 @f2() {
ret i1 icmp eq (i8* inttoptr (i16 1 to i8*), i8* inttoptr (i16 2 to i8*))
}