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implement PR4424: 0/x is always 0 for integer division.

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llvm-svn: 73835
This commit is contained in:
Chris Lattner 2009-06-21 01:15:55 +00:00
parent 580eecebbd
commit affcc71da2
2 changed files with 19 additions and 0 deletions
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7
lib/VMCore/ConstantFold.cpp
View File

@ -773,6 +773,13 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
}
}
}
// 0 / x -> 0.
if ((Opcode == Instruction::UDiv ||
Opcode == Instruction::SDiv) &&
CI1->isZero())
return const_cast<Constant*>(C1);
} else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
APFloat C1V = CFP1->getValueAPF();

12
test/Transforms/ConstProp/div-zero.ll Normal file
View File

@ -0,0 +1,12 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {ret i32 0}
; PR4424
declare void @ext()
define i32 @foo(i32 %ptr) {
entry:
%zero = sub i32 %ptr, %ptr ; <i32> [#uses=1]
%div_zero = sdiv i32 %zero, ptrtoint (i32* getelementptr (i32* null,
i32 1) to i32) ; <i32> [#uses=1]
ret i32 %div_zero
}