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Fix a reassociate crash on sozefx when compiling with dragonegg+gcc-4.7 due to

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the optimizers producing a multiply expression with more multiplications than
the original (!).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159426 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2012-06-29 13:25:06 +00:00
parent 06cb8ed006
commit 96d2eff5c6
2 changed files with 24 additions and 5 deletions
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18
lib/Transforms/Scalar/Reassociate.cpp
View File

@ -674,8 +674,6 @@ void Reassociate::RewriteExprTree(BinaryOperator *I,
// Flags are cleared from the operator in ExpressionChanged up to I inclusive.
BinaryOperator *ExpressionChanged = 0;
for (unsigned i = 0; ; ++i) {
assert(!NodesToRewrite.empty() &&
"Optimized expressions has more nodes than original!");
BinaryOperator *Op = NodesToRewrite.pop_back_val();
// The last operation (which comes earliest in the IR) is special as both
@ -753,9 +751,19 @@ void Reassociate::RewriteExprTree(BinaryOperator *I,
}
// Otherwise, grab a spare node from the original expression and use that as
// the left-hand side.
assert(!NodesToRewrite.empty() &&
"Optimized expressions has more nodes than original!");
// the left-hand side. If there are no nodes left then the optimizers made
// an expression with more nodes than the original! This usually means that
// they did something stupid but it might mean that the problem was just too
// hard (finding the mimimal number of multiplications needed to realize a
// multiplication expression is NP-complete). Whatever the reason, smart or
// stupid, create a new node if there are none left.
if (NodesToRewrite.empty()) {
Constant *Undef = UndefValue::get(I->getType());
BinaryOperator *N = BinaryOperator::Create(Instruction::BinaryOps(Opcode),
Undef, Undef, "", I);
NodesToRewrite.push_back(N);
}
DEBUG(dbgs() << "RA: " << *Op << '\n');
Op->setOperand(0, NodesToRewrite.back());
DEBUG(dbgs() << "TO: " << *Op << '\n');

11
test/Transforms/Reassociate/crash.ll
View File

@ -133,3 +133,14 @@ define i8 @f0(i8 %x) {
%t7 = mul i8 %t6, %t0
ret i8 %t7
}
define i32 @sozefx_(i32 %x, i32 %y) {
%t0 = sub i32 %x, %x
%t1 = mul i32 %t0, %t0
%t2 = mul i32 %x, %t0
%t3 = mul i32 %t1, %t1
%t4 = add i32 %t2, %t3
%t5 = mul i32 %x, %y
%t6 = add i32 %t4, %t5
ret i32 %t6
}