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Teach the constant folder how to handle a few simple i1 cases.
llvm-svn: 82340
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b29a51b4d4
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@ -1010,6 +1010,37 @@ Constant *llvm::ConstantFoldBinaryInstruction(LLVMContext &Context,
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}
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}
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// i1 can be simplified in many cases.
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if (C1->getType() == Type::getInt1Ty(Context)) {
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switch (Opcode) {
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case Instruction::Add:
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case Instruction::Sub:
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return ConstantExpr::getXor(const_cast<Constant*>(C1),
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const_cast<Constant*>(C2));
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case Instruction::Mul:
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return ConstantExpr::getAnd(const_cast<Constant*>(C1),
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const_cast<Constant*>(C2));
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case Instruction::Shl:
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case Instruction::LShr:
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case Instruction::AShr:
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// We can assume that C2 == 0. If it were one the result would be
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// undefined because the shift value is as large as the bitwidth.
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return const_cast<Constant*>(C1);
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case Instruction::SDiv:
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case Instruction::UDiv:
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// We can assume that C2 == 1. If it were zero the result would be
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// undefined through division by zero.
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return const_cast<Constant*>(C1);
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case Instruction::URem:
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case Instruction::SRem:
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// We can assume that C2 == 1. If it were zero the result would be
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// undefined through division by zero.
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return ConstantInt::getFalse(Context);
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default:
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break;
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}
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}
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// We don't know how to fold this.
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return 0;
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}
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@ -0,0 +1,25 @@
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; RUN: llvm-as < %s | llvm-dis | FileCheck %s
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@X = external global i8
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@Y = external global i8
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@Z = external global i8
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global i1 add (i1 icmp ult (i8* @X, i8* @Y), i1 icmp ult (i8* @X, i8* @Z))
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; CHECK: xor
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global i1 sub (i1 icmp ult (i8* @X, i8* @Y), i1 icmp ult (i8* @X, i8* @Z))
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; CHECK: xor
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global i1 mul (i1 icmp ult (i8* @X, i8* @Y), i1 icmp ult (i8* @X, i8* @Z))
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; CHECK: and
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global i1 sdiv (i1 icmp ult (i8* @X, i8* @Y), i1 icmp ult (i8* @X, i8* @Z))
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; CHECK-NOT: @Z
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; CHECK: i1 icmp ult (i8* @X, i8* @Y)
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global i1 udiv (i1 icmp ult (i8* @X, i8* @Y), i1 icmp ult (i8* @X, i8* @Z))
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; CHECK-NOT: @Z
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; CHECK: i1 icmp ult (i8* @X, i8* @Y)
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global i1 srem (i1 icmp ult (i8* @X, i8* @Y), i1 icmp ult (i8* @X, i8* @Z))
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; CHECK-NOT: icmp
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; CHECK: i1 false
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global i1 urem (i1 icmp ult (i8* @X, i8* @Y), i1 icmp ult (i8* @X, i8* @Z))
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; CHECK-NOT: icmp
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; CHECK: i1 false
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