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simplify and merge a bunch of code. Instead of comparing against

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the min/max values for an integer type, compare against the min/max
values we can prove contain the input.  This might be a tighter bound,
so this is general goodness.

llvm-svn: 53446
This commit is contained in:
Chris Lattner 2008-07-11 05:40:05 +00:00
parent d1198896ae
commit 3d40848bfd
1 changed files with 52 additions and 81 deletions
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133
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -2964,24 +2964,6 @@ Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
return commonRemTransforms(I);
}
// isMaxValueMinusOne - return true if this is Max-1
static bool isMaxValueMinusOne(const ConstantInt *C, bool isSigned) {
uint32_t TypeBits = C->getType()->getPrimitiveSizeInBits();
if (!isSigned)
return C->getValue() == APInt::getAllOnesValue(TypeBits) - 1;
return C->getValue() == APInt::getSignedMaxValue(TypeBits)-1;
}
// isMinValuePlusOne - return true if this is Min+1
static bool isMinValuePlusOne(const ConstantInt *C, bool isSigned) {
if (!isSigned)
return C->getValue() == 1; // unsigned
// Calculate 1111111111000000000000
uint32_t TypeBits = C->getType()->getPrimitiveSizeInBits();
return C->getValue() == APInt::getSignedMinValue(TypeBits)+1;
}
// isOneBitSet - Return true if there is exactly one bit set in the specified
// constant.
static bool isOneBitSet(const ConstantInt *CI) {
@ -5274,63 +5256,16 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
return new ICmpInst(ICmpInst::ICMP_SGT, Op0, SubOne(CI));
}
switch (I.getPredicate()) {
default: break;
case ICmpInst::ICMP_ULT: // A <u MIN -> FALSE
if (CI->isMinValue(false))
return ReplaceInstUsesWith(I, ConstantInt::getFalse());
if (CI->isMaxValue(false)) // A <u MAX -> A != MAX
return new ICmpInst(ICmpInst::ICMP_NE, Op0,Op1);
if (isMinValuePlusOne(CI,false)) // A <u MIN+1 -> A == MIN
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, SubOne(CI));
// (x <u 2147483648) -> (x >s -1) -> true if sign bit clear
if (CI->isMinValue(true))
return new ICmpInst(ICmpInst::ICMP_SGT, Op0,
ConstantInt::getAllOnesValue(Op0->getType()));
break;
case ICmpInst::ICMP_SLT:
if (CI->isMinValue(true)) // A <s MIN -> FALSE
return ReplaceInstUsesWith(I, ConstantInt::getFalse());
if (CI->isMaxValue(true)) // A <s MAX -> A != MAX
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (isMinValuePlusOne(CI,true)) // A <s MIN+1 -> A == MIN
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, SubOne(CI));
break;
case ICmpInst::ICMP_UGT:
if (CI->isMaxValue(false)) // A >u MAX -> FALSE
return ReplaceInstUsesWith(I, ConstantInt::getFalse());
if (CI->isMinValue(false)) // A >u MIN -> A != MIN
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (isMaxValueMinusOne(CI, false)) // A >u MAX-1 -> A == MAX
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, AddOne(CI));
// (x >u 2147483647) -> (x <s 0) -> true if sign bit set
if (CI->isMaxValue(true))
return new ICmpInst(ICmpInst::ICMP_SLT, Op0,
ConstantInt::getNullValue(Op0->getType()));
break;
case ICmpInst::ICMP_SGT:
if (CI->isMaxValue(true)) // A >s MAX -> FALSE
return ReplaceInstUsesWith(I, ConstantInt::getFalse());
if (CI->isMinValue(true)) // A >s MIN -> A != MIN
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (isMaxValueMinusOne(CI, true)) // A >s MAX-1 -> A == MAX
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, AddOne(CI));
break;
}
// See if we can fold the comparison based on bits known to be zero or one
// in the input. If this comparison is a normal comparison, it demands all
// See if we can fold the comparison based on range information we can get
// by checking whether bits are known to be zero or one in the input.
uint32_t BitWidth = cast<IntegerType>(Ty)->getBitWidth();
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
// If this comparison is a normal comparison, it demands all
// bits, if it is a sign bit comparison, it only demands the sign bit.
bool UnusedBit;
bool isSignBit = isSignBitCheck(I.getPredicate(), CI, UnusedBit);
uint32_t BitWidth = cast<IntegerType>(Ty)->getBitWidth();
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
if (SimplifyDemandedBits(Op0,
isSignBit ? APInt::getSignBit(BitWidth)
: APInt::getAllOnesValue(BitWidth),
@ -5341,12 +5276,22 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
// in. Compute the Min, Max and RHS values based on the known bits. For the
// EQ and NE we use unsigned values.
APInt Min(BitWidth, 0), Max(BitWidth, 0);
const APInt& RHSVal = CI->getValue();
if (ICmpInst::isSignedPredicate(I.getPredicate()))
ComputeSignedMinMaxValuesFromKnownBits(Ty, KnownZero, KnownOne, Min, Max);
else
ComputeUnsignedMinMaxValuesFromKnownBits(Ty, KnownZero, KnownOne,Min,Max);
// If Min and Max are known to be the same, then SimplifyDemandedBits
// figured out that the LHS is a constant. Just constant fold this now so
// that code below can assume that Min != Max.
if (Min == Max)
return ReplaceInstUsesWith(I, ConstantExpr::getICmp(I.getPredicate(),
ConstantInt::get(Min),
CI));
// Based on the range information we know about the LHS, see if we can
// simplify this comparison. For example, (x&4) < 8 is always true.
const APInt &RHSVal = CI->getValue();
switch (I.getPredicate()) { // LE/GE have been folded already.
default: assert(0 && "Unknown icmp opcode!");
case ICmpInst::ICMP_EQ:
@ -5358,30 +5303,56 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
return ReplaceInstUsesWith(I, ConstantInt::getTrue());
break;
case ICmpInst::ICMP_ULT:
if (Max.ult(RHSVal))
if (Max.ult(RHSVal)) // A <u C -> true iff max(A) < C
return ReplaceInstUsesWith(I, ConstantInt::getTrue());
if (Min.uge(RHSVal))
if (Min.uge(RHSVal)) // A <u C -> false iff min(A) >= C
return ReplaceInstUsesWith(I, ConstantInt::getFalse());
if (RHSVal == Max) // A <u MAX -> A != MAX
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (RHSVal == Min+1) // A <u MIN+1 -> A == MIN
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, SubOne(CI));
// (x <u 2147483648) -> (x >s -1) -> true if sign bit clear
if (CI->isMinValue(true))
return new ICmpInst(ICmpInst::ICMP_SGT, Op0,
ConstantInt::getAllOnesValue(Op0->getType()));
break;
case ICmpInst::ICMP_UGT:
if (Min.ugt(RHSVal))
if (Min.ugt(RHSVal)) // A >u C -> true iff min(A) > C
return ReplaceInstUsesWith(I, ConstantInt::getTrue());
if (Max.ule(RHSVal))
if (Max.ule(RHSVal)) // A >u C -> false iff max(A) <= C
return ReplaceInstUsesWith(I, ConstantInt::getFalse());
if (RHSVal == Min) // A >u MIN -> A != MIN
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (RHSVal == Max-1) // A >u MAX-1 -> A == MAX
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, AddOne(CI));
// (x >u 2147483647) -> (x <s 0) -> true if sign bit set
if (CI->isMaxValue(true))
return new ICmpInst(ICmpInst::ICMP_SLT, Op0,
ConstantInt::getNullValue(Op0->getType()));
break;
case ICmpInst::ICMP_SLT:
if (Max.slt(RHSVal))
if (Max.slt(RHSVal)) // A <s C -> true iff max(A) < C
return ReplaceInstUsesWith(I, ConstantInt::getTrue());
if (Min.sgt(RHSVal))
if (Min.sgt(RHSVal)) // A <s C -> false iff min(A) >= C
return ReplaceInstUsesWith(I, ConstantInt::getFalse());
if (Max == RHSVal) // A <s MAX -> A != MAX
if (RHSVal == Max) // A <s MAX -> A != MAX
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (RHSVal == Min-1) // A <s MIN+1 -> A == MIN
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
break;
case ICmpInst::ICMP_SGT:
if (Min.sgt(RHSVal))
if (Min.sgt(RHSVal)) // A >s C -> true iff min(A) > C
return ReplaceInstUsesWith(I, ConstantInt::getTrue());
if (Max.sle(RHSVal))
if (Max.sle(RHSVal)) // A >s C -> false iff max(A) <= C
return ReplaceInstUsesWith(I, ConstantInt::getFalse());
if (RHSVal == Min) // A >s MIN -> A != MIN
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (RHSVal == Max-1) // A >s MAX-1 -> A == MAX
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, AddOne(CI));
break;
}