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Fix a nondeterminism in the ARM assembler.
Adding arbitrary records to ARM.td would break basic-arm-instructions.s because selection of nop vs mov r0,r0 was ambiguous (this will be tested by a subsequent addition to ARM.td). An imperfect but sensible fix is to give precedence to match rules that have more constraints. llvm-svn: 162824
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@ -488,6 +488,15 @@ struct MatchableInfo {
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return false;
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}
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// Give matches that require more features higher precedence. This is useful
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// because we cannot define AssemblerPredicates with the negation of
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// processor features. For example, ARM v6 "nop" may be either a HINT or
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// MOV. With v6, we want to match HINT. The assembler has no way to
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// predicate MOV under "NoV6", but HINT will always match first because it
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// requires V6 while MOV does not.
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if (RequiredFeatures.size() != RHS.RequiredFeatures.size())
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return RequiredFeatures.size() > RHS.RequiredFeatures.size();
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return false;
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}
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