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Switch on the use of arbitrary precision integers in scalar evolution. This will
bail after 256-bits to avoid producing code that the backends can't handle. Previously, we capped it at 64-bits, preferring to miscompile in those cases. This change also reverts much of r52248 because the invariants the code was expecting are now being met. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53812 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -538,20 +538,12 @@ static SCEVHandle BinomialCoefficient(SCEVHandle It, unsigned K,
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assert(K < 9 && "We cannot handle such long AddRecs yet.");
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// FIXME: A temporary hack to remove in future. Arbitrary precision integers
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// aren't supported by the code generator yet. For the dividend, the bitwidth
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// we use is the smallest power of 2 greater or equal to K*W and less or equal
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// to 64. Note that setting the upper bound for bitwidth may still lead to
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// miscompilation in some cases.
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unsigned DividendBits = 1U << Log2_32_Ceil(K * It->getBitWidth());
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if (DividendBits > 64)
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DividendBits = 64;
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#if 0 // Waiting for the APInt support in the code generator...
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unsigned DividendBits = K * It->getBitWidth();
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#endif
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if (DividendBits > 256)
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return new SCEVCouldNotCompute();
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const IntegerType *DividendTy = IntegerType::get(DividendBits);
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const SCEVHandle ExIt = SE.getTruncateOrZeroExtend(It, DividendTy);
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const SCEVHandle ExIt = SE.getZeroExtendExpr(It, DividendTy);
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// The final number of bits we need to perform the division is the maximum of
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// dividend and divisor bitwidths.
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@ -573,12 +565,7 @@ static SCEVHandle BinomialCoefficient(SCEVHandle It, unsigned K,
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Dividend *= N-(K-1);
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if (DividendTy != DivisionTy)
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Dividend = Dividend.zext(DivisionTy->getBitWidth());
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APInt Result = Dividend.udiv(Divisor);
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if (Result.getBitWidth() != It->getBitWidth())
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Result = Result.trunc(It->getBitWidth());
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return SE.getConstant(Result);
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return SE.getConstant(Dividend.udiv(Divisor).trunc(It->getBitWidth()));
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}
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SCEVHandle Dividend = ExIt;
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@ -587,11 +574,10 @@ static SCEVHandle BinomialCoefficient(SCEVHandle It, unsigned K,
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SE.getMulExpr(Dividend,
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SE.getMinusSCEV(ExIt, SE.getIntegerSCEV(i, DividendTy)));
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return SE.getTruncateOrZeroExtend(
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SE.getUDivExpr(
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SE.getTruncateOrZeroExtend(Dividend, DivisionTy),
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SE.getConstant(Divisor)
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), It->getType());
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if (DividendTy != DivisionTy)
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Dividend = SE.getZeroExtendExpr(Dividend, DivisionTy);
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return SE.getTruncateExpr(SE.getUDivExpr(Dividend, SE.getConstant(Divisor)),
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It->getType());
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}
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/// evaluateAtIteration - Return the value of this chain of recurrences at
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