[llvm-commits] [llvm] r121100 - in /llvm/trunk: lib/Transforms/IPO/GlobalOpt.cpp test/Transforms/GlobalOpt/ctor-list-opt-constexpr.ll
Chris Lattner
sabre at nondot.org
Mon Dec 6 17:59:33 PST 2010
Author: lattner
Date: Mon Dec 6 19:59:32 2010
New Revision: 121100
URL: http://llvm.org/viewvc/llvm-project?rev=121100&view=rev
Log:
fix PR8710 - teach global opt that some constantexprs are too complex to
put in a global variable's initializer.
Added:
llvm/trunk/test/Transforms/GlobalOpt/ctor-list-opt-constexpr.ll
Modified:
llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
Modified: llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp?rev=121100&r1=121099&r2=121100&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp Mon Dec 6 19:59:32 2010
@@ -2046,14 +2046,82 @@
}
-static Constant *getVal(DenseMap<Value*, Constant*> &ComputedValues,
- Value *V) {
+static Constant *getVal(DenseMap<Value*, Constant*> &ComputedValues, Value *V) {
if (Constant *CV = dyn_cast<Constant>(V)) return CV;
Constant *R = ComputedValues[V];
assert(R && "Reference to an uncomputed value!");
return R;
}
+static inline bool
+isSimpleEnoughValueToCommit(Constant *C,
+ SmallPtrSet<Constant*, 8> &SimpleConstants);
+
+
+/// isSimpleEnoughValueToCommit - Return true if the specified constant can be
+/// handled by the code generator. We don't want to generate something like:
+/// void *X = &X/42;
+/// because the code generator doesn't have a relocation that can handle that.
+///
+/// This function should be called if C was not found (but just got inserted)
+/// in SimpleConstants to avoid having to rescan the same constants all the
+/// time.
+static bool isSimpleEnoughValueToCommitHelper(Constant *C,
+ SmallPtrSet<Constant*, 8> &SimpleConstants) {
+ // Simple integer, undef, constant aggregate zero, global addresses, etc are
+ // all supported.
+ if (C->getNumOperands() == 0 || isa<BlockAddress>(C) ||
+ isa<GlobalValue>(C))
+ return true;
+
+ // Aggregate values are safe if all their elements are.
+ if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) ||
+ isa<ConstantVector>(C)) {
+ for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) {
+ Constant *Op = cast<Constant>(C->getOperand(i));
+ if (!isSimpleEnoughValueToCommit(Op, SimpleConstants))
+ return false;
+ }
+ return true;
+ }
+
+ // We don't know exactly what relocations are allowed in constant expressions,
+ // so we allow &global+constantoffset, which is safe and uniformly supported
+ // across targets.
+ ConstantExpr *CE = cast<ConstantExpr>(C);
+ switch (CE->getOpcode()) {
+ case Instruction::BitCast:
+ case Instruction::IntToPtr:
+ case Instruction::PtrToInt:
+ // These casts are always fine if the casted value is.
+ return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants);
+
+ // GEP is fine if it is simple + constant offset.
+ case Instruction::GetElementPtr:
+ for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
+ if (!isa<ConstantInt>(CE->getOperand(i)))
+ return false;
+ return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants);
+
+ case Instruction::Add:
+ // We allow simple+cst.
+ if (!isa<ConstantInt>(CE->getOperand(1)))
+ return false;
+ return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants);
+ }
+ return false;
+}
+
+static inline bool
+isSimpleEnoughValueToCommit(Constant *C,
+ SmallPtrSet<Constant*, 8> &SimpleConstants) {
+ // If we already checked this constant, we win.
+ if (!SimpleConstants.insert(C)) return true;
+ // Check the constant.
+ return isSimpleEnoughValueToCommitHelper(C, SimpleConstants);
+}
+
+
/// isSimpleEnoughPointerToCommit - Return true if this constant is simple
/// enough for us to understand. In particular, if it is a cast of something,
/// we punt. We basically just support direct accesses to globals and GEP's of
@@ -2219,7 +2287,8 @@
const SmallVectorImpl<Constant*> &ActualArgs,
std::vector<Function*> &CallStack,
DenseMap<Constant*, Constant*> &MutatedMemory,
- std::vector<GlobalVariable*> &AllocaTmps) {
+ std::vector<GlobalVariable*> &AllocaTmps,
+ SmallPtrSet<Constant*, 8> &SimpleConstants) {
// Check to see if this function is already executing (recursion). If so,
// bail out. TODO: we might want to accept limited recursion.
if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
@@ -2254,7 +2323,13 @@
if (!isSimpleEnoughPointerToCommit(Ptr))
// If this is too complex for us to commit, reject it.
return false;
+
Constant *Val = getVal(Values, SI->getOperand(0));
+
+ // If this might be too difficult for the backend to handle (e.g. the addr
+ // of one global variable divided by another) then we can't commit it.
+ if (!isSimpleEnoughValueToCommit(Val, SimpleConstants))
+ return false;
MutatedMemory[Ptr] = Val;
} else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
InstResult = ConstantExpr::get(BO->getOpcode(),
@@ -2331,7 +2406,7 @@
Constant *RetVal;
// Execute the call, if successful, use the return value.
if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
- MutatedMemory, AllocaTmps))
+ MutatedMemory, AllocaTmps, SimpleConstants))
return false;
InstResult = RetVal;
}
@@ -2417,11 +2492,16 @@
/// unbounded.
std::vector<Function*> CallStack;
+ /// SimpleConstants - These are constants we have checked and know to be
+ /// simple enough to live in a static initializer of a global.
+ SmallPtrSet<Constant*, 8> SimpleConstants;
+
// Call the function.
Constant *RetValDummy;
bool EvalSuccess = EvaluateFunction(F, RetValDummy,
SmallVector<Constant*, 0>(), CallStack,
- MutatedMemory, AllocaTmps);
+ MutatedMemory, AllocaTmps,
+ SimpleConstants);
if (EvalSuccess) {
// We succeeded at evaluation: commit the result.
DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
Added: llvm/trunk/test/Transforms/GlobalOpt/ctor-list-opt-constexpr.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GlobalOpt/ctor-list-opt-constexpr.ll?rev=121100&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/GlobalOpt/ctor-list-opt-constexpr.ll (added)
+++ llvm/trunk/test/Transforms/GlobalOpt/ctor-list-opt-constexpr.ll Mon Dec 6 19:59:32 2010
@@ -0,0 +1,23 @@
+; RUN: opt -globalopt %s -S | FileCheck %s
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-apple-darwin10.0.0"
+
+%0 = type { i32, void ()* }
+%struct.foo = type { i32* }
+
+ at G = global i32 0, align 4
+ at H = global i32 0, align 4
+ at X = global %struct.foo zeroinitializer, align 8
+ at llvm.global_ctors = appending global [1 x %0] [%0 { i32 65535, void ()* @init }]
+
+; PR8710 - GlobalOpt shouldn't change the global's initializer to have this
+; arbitrary constant expression, the code generator can't handle it.
+define internal void @init() {
+entry:
+ %tmp = getelementptr inbounds %struct.foo* @X, i32 0, i32 0
+ store i32* inttoptr (i64 sdiv (i64 ptrtoint (i32* @G to i64), i64 ptrtoint (i32* @H to i64)) to i32*), i32** %tmp, align 8
+ ret void
+}
+
+; CHECK: @init
+; CHECK: store i32*
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