Hi,
ConstantExprs are extremely opaque in LLVM, and it's very difficult to
transform them in any way.
A use case I'm thinking of is from a design constraint coming from SPIR:
https://groups.google.com/d/msg/llvm-dev/71tgtvash74/a94eadJIqB0J
Basically we want to change an operand of a constant expression from a
Constant to a Value, which requires unwrapping the expression which is
impossible with the current API.
The attached patch implements a simple extra API function to retrieve an
Instruction* equivalent for a ConstantExpr. With this addition, dealing
with the constraints imposed by SPIR is actually possible without
horrible hackery...
The test is nasty, I admit. I had to find a way to stop the constant
folder folding away what I was trying to test, which means the test
can't just use trivial i32 operands (it uses a GlobalValue bitcasted to
an i32/i64 to fool the optimiser).
What do you think?
Cheers,
James
Index: unittests/VMCore/ConstantsTest.cpp
===================================================================
--- unittests/VMCore/ConstantsTest.cpp (revision 167130)
+++ unittests/VMCore/ConstantsTest.cpp (working copy)
@@ -8,8 +8,11 @@
//===----------------------------------------------------------------------===//
#include "llvm/Constants.h"
+#include "llvm/Instruction.h"
+#include "llvm/InstrTypes.h"
#include "llvm/DerivedTypes.h"
#include "llvm/LLVMContext.h"
+#include "llvm/Module.h"
#include "gtest/gtest.h"
namespace llvm {
@@ -118,5 +121,108 @@
EXPECT_TRUE(isa<ConstantFP>(X));
}
+#define CHECK(x, y) { \
+ std::string __s; \
+ raw_string_ostream __o(__s); \
+ cast<ConstantExpr>(x)->getAsInstruction()->print(__o); \
+ __o.flush(); \
+ EXPECT_EQ(std::string(" <badref> = " y), __s); \
+ }
+
+TEST(ConstantsTest, AsInstructionsTest) {
+ Module *M = new Module("MyModule", getGlobalContext());
+
+ Type *Int64Ty = Type::getInt64Ty(getGlobalContext());
+ Type *Int32Ty = Type::getInt32Ty(getGlobalContext());
+ Type *Int16Ty = Type::getInt16Ty(getGlobalContext());
+ Type *Int1Ty = Type::getInt1Ty(getGlobalContext());
+ Type *FloatTy = Type::getFloatTy(getGlobalContext());
+ Type *DoubleTy = Type::getDoubleTy(getGlobalContext());
+
+ Constant *Global = M->getOrInsertGlobal("dummy",
+ PointerType::getUnqual(Int32Ty));
+ Constant *Global2 = M->getOrInsertGlobal("dummy2",
+ PointerType::getUnqual(Int32Ty));
+
+ Constant *P0 = ConstantExpr::getPtrToInt(Global, Int32Ty);
+ Constant *P1 = ConstantExpr::getUIToFP(P0, FloatTy);
+ Constant *P2 = ConstantExpr::getUIToFP(P0, DoubleTy);
+ Constant *P3 = ConstantExpr::getTrunc(P0, Int1Ty);
+ Constant *P4 = ConstantExpr::getPtrToInt(Global2, Int32Ty);
+ Constant *P5 = ConstantExpr::getUIToFP(P4, FloatTy);
+ Constant *P6 = ConstantExpr::getBitCast(P4, VectorType::get(Int16Ty, 2));
+
+ Constant *One = ConstantInt::get(Int32Ty, 1);
+
+ #define P0STR "ptrtoint (i32** @dummy to i32)"
+ #define P1STR "uitofp (i32 ptrtoint (i32** @dummy to i32) to float)"
+ #define P2STR "uitofp (i32 ptrtoint (i32** @dummy to i32) to double)"
+ #define P3STR "ptrtoint (i32** @dummy to i1)"
+ #define P4STR "ptrtoint (i32** @dummy2 to i32)"
+ #define P5STR "uitofp (i32 ptrtoint (i32** @dummy2 to i32) to float)"
+ #define P6STR "bitcast (i32 ptrtoint (i32** @dummy2 to i32) to <2 x i16>)"
+
+ CHECK(ConstantExpr::getNeg(P0), "sub i32 0, " P0STR);
+ CHECK(ConstantExpr::getFNeg(P1), "fsub float -0.000000e+00, " P1STR);
+ CHECK(ConstantExpr::getNot(P0), "xor i32 " P0STR ", -1");
+ CHECK(ConstantExpr::getAdd(P0, P0), "add i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getAdd(P0, P0, false, true), "add nsw i32 " P0STR ", "
+ P0STR);
+ CHECK(ConstantExpr::getAdd(P0, P0, true, true), "add nuw nsw i32 " P0STR ", "
+ P0STR);
+ CHECK(ConstantExpr::getFAdd(P1, P1), "fadd float " P1STR ", " P1STR);
+ CHECK(ConstantExpr::getSub(P0, P0), "sub i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getFSub(P1, P1), "fsub float " P1STR ", " P1STR);
+ CHECK(ConstantExpr::getMul(P0, P0), "mul i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getFMul(P1, P1), "fmul float " P1STR ", " P1STR);
+ CHECK(ConstantExpr::getUDiv(P0, P0), "udiv i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getSDiv(P0, P0), "sdiv i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getFDiv(P1, P1), "fdiv float " P1STR ", " P1STR);
+ CHECK(ConstantExpr::getURem(P0, P0), "urem i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getSRem(P0, P0), "srem i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getFRem(P1, P1), "frem float " P1STR ", " P1STR);
+ CHECK(ConstantExpr::getAnd(P0, P0), "and i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getOr(P0, P0), "or i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getXor(P0, P0), "xor i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getShl(P0, P0), "shl i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getShl(P0, P0, true), "shl nuw i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getShl(P0, P0, false, true), "shl nsw i32 " P0STR ", "
+ P0STR);
+ CHECK(ConstantExpr::getLShr(P0, P0, false), "lshr i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getLShr(P0, P0, true), "lshr exact i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getAShr(P0, P0, false), "ashr i32 " P0STR ", " P0STR);
+ CHECK(ConstantExpr::getAShr(P0, P0, true), "ashr exact i32 " P0STR ", " P0STR);
+
+ CHECK(ConstantExpr::getSExt(P0, Int64Ty), "sext i32 " P0STR " to i64");
+ CHECK(ConstantExpr::getZExt(P0, Int64Ty), "zext i32 " P0STR " to i64");
+ CHECK(ConstantExpr::getFPTrunc(P2, FloatTy), "fptrunc double " P2STR
+ " to float");
+ CHECK(ConstantExpr::getFPExtend(P1, DoubleTy), "fpext float " P1STR
+ " to double");
+
+ CHECK(ConstantExpr::getExactUDiv(P0, P0), "udiv exact i32 " P0STR ", " P0STR);
+
+ CHECK(ConstantExpr::getSelect(P3, P0, P4), "select i1 " P3STR ", i32 " P0STR
+ ", i32 " P4STR);
+ CHECK(ConstantExpr::getICmp(CmpInst::ICMP_EQ, P0, P4), "icmp eq i32 " P0STR
+ ", " P4STR);
+ CHECK(ConstantExpr::getFCmp(CmpInst::FCMP_ULT, P1, P5), "fcmp ult float "
+ P1STR ", " P5STR);
+
+ std::vector<Constant*> V;
+ V.push_back(One);
+ // FIXME: getGetElementPtr() actually creates an inbounds ConstantGEP,
+ // not a normal one!
+ //CHECK(ConstantExpr::getGetElementPtr(Global, V, false),
+ // "getelementptr i32** @dummy, i32 1");
+ CHECK(ConstantExpr::getInBoundsGetElementPtr(Global, V),
+ "getelementptr inbounds i32** @dummy, i32 1");
+
+ CHECK(ConstantExpr::getExtractElement(P6, One), "extractelement <2 x i16> "
+ P6STR ", i32 1");
+}
+
+#undef CHECK
+
} // end anonymous namespace
} // end namespace llvm
Index: lib/VMCore/Constants.cpp
===================================================================
--- lib/VMCore/Constants.cpp (revision 167130)
+++ lib/VMCore/Constants.cpp (working copy)
@@ -2642,3 +2642,66 @@
// Delete the old constant!
destroyConstant();
}
+
+Instruction *ConstantExpr::getAsInstruction() {
+ SmallVector<Value*,4> ValueOperands;
+ for (op_iterator I = op_begin(), E = op_end(); I != E; ++I)
+ ValueOperands.push_back(cast<Value>(I));
+
+ ArrayRef<Value*> Ops(ValueOperands);
+
+ switch (getOpcode()) {
+ case Instruction::Trunc:
+ case Instruction::ZExt:
+ case Instruction::SExt:
+ case Instruction::FPTrunc:
+ case Instruction::FPExt:
+ case Instruction::UIToFP:
+ case Instruction::SIToFP:
+ case Instruction::FPToUI:
+ case Instruction::FPToSI:
+ case Instruction::PtrToInt:
+ case Instruction::IntToPtr:
+ case Instruction::BitCast:
+ return CastInst::Create((Instruction::CastOps)getOpcode(),
+ Ops[0], getType());
+ case Instruction::Select:
+ return SelectInst::Create(Ops[0], Ops[1], Ops[2]);
+ case Instruction::InsertElement:
+ return InsertElementInst::Create(Ops[0], Ops[1], Ops[2]);
+ case Instruction::ExtractElement:
+ return ExtractElementInst::Create(Ops[0], Ops[1]);
+ case Instruction::InsertValue:
+ return InsertValueInst::Create(Ops[0], Ops[1], getIndices());
+ case Instruction::ExtractValue:
+ return ExtractValueInst::Create(Ops[0], getIndices());
+ case Instruction::ShuffleVector:
+ return new ShuffleVectorInst(Ops[0], Ops[1], Ops[2]);
+
+ case Instruction::GetElementPtr:
+ if (cast<GEPOperator>(this)->isInBounds())
+ return GetElementPtrInst::CreateInBounds(Ops[0], Ops.slice(1));
+ else
+ return GetElementPtrInst::Create(Ops[0], Ops.slice(1));
+
+ case Instruction::ICmp:
+ case Instruction::FCmp:
+ return CmpInst::Create((Instruction::OtherOps)getOpcode(),
+ getPredicate(), Ops[0], Ops[1]);
+
+ default:
+ assert(getNumOperands() == 2 && "Must be binary operator?");
+ BinaryOperator *BO =
+ BinaryOperator::Create((Instruction::BinaryOps)getOpcode(),
+ Ops[0], Ops[1]);
+ if (isa<OverflowingBinaryOperator>(BO)) {
+ BO->setHasNoUnsignedWrap(SubclassOptionalData &
+ OverflowingBinaryOperator::NoUnsignedWrap);
+ BO->setHasNoSignedWrap(SubclassOptionalData &
+ OverflowingBinaryOperator::NoSignedWrap);
+ }
+ if (isa<PossiblyExactOperator>(BO))
+ BO->setIsExact(SubclassOptionalData & PossiblyExactOperator::IsExact);
+ return BO;
+ }
+}
Index: include/llvm/Constants.h
===================================================================
--- include/llvm/Constants.h (revision 167130)
+++ include/llvm/Constants.h (working copy)
@@ -1076,6 +1076,10 @@
/// current one.
Constant *getWithOperands(ArrayRef<Constant*> Ops, Type *Ty) const;
+ /// getAsInstruction - Returns an Instruction which implements the same operation
+ /// as this ConstantExpr. The instruction is not linked to any basic block.
+ Instruction *getAsInstruction();
+
virtual void destroyConstant();
virtual void replaceUsesOfWithOnConstant(Value *From, Value *To, Use *U);
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