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Teach ScalarEvolution how to recognize another xor(and(x, C), C) case.
If C is a single bit and the and gets analyzed as a truncate and zero-extend, the xor can be represnted as an add. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73664 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -2453,10 +2453,25 @@ SCEVHandle ScalarEvolution::createSCEV(Value *V) {
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LCI->getValue() == CI->getValue())
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if (const SCEVZeroExtendExpr *Z =
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dyn_cast<SCEVZeroExtendExpr>(getSCEV(U->getOperand(0)))) {
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SCEVHandle ZO = Z->getOperand();
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if (APIntOps::isMask(getTypeSizeInBits(ZO->getType()),
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CI->getValue()))
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return getZeroExtendExpr(getNotSCEV(ZO), U->getType());
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const Type *UTy = U->getType();
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SCEVHandle Z0 = Z->getOperand();
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const Type *Z0Ty = Z0->getType();
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unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
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// If C is a low-bits mask, the zero extend is zerving to
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// mask off the high bits. Complement the operand and
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// re-apply the zext.
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if (APIntOps::isMask(Z0TySize, CI->getValue()))
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return getZeroExtendExpr(getNotSCEV(Z0), UTy);
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// If C is a single bit, it may be in the sign-bit position
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// before the zero-extend. In this case, represent the xor
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// using an add, which is equivalent, and re-apply the zext.
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APInt Trunc = APInt(CI->getValue()).trunc(Z0TySize);
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if (APInt(Trunc).zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
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Trunc.isSignBit())
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return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
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UTy);
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}
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}
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break;
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@ -1,6 +1,7 @@
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; RUN: llvm-as < %s | opt -scalar-evolution -disable-output -analyze | grep {\\--> %z}
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; RUN: llvm-as < %s | opt -scalar-evolution -disable-output -analyze \
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; RUN: | grep {\\--> (zext i4 (-8 + (trunc i64 (8 \\* %x) to i4)) to i64)}
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; ScalarEvolution shouldn't try to analyze %s into something like
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; ScalarEvolution shouldn't try to analyze %z into something like
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; --> (zext i4 (-1 + (-1 * (trunc i64 (8 * %x) to i4))) to i64)
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define i64 @foo(i64 %x) {
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