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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am currently trying to analyze instructions in a loop, in the mid-end to determine if they are using a specific operand (another instruction). The problem is that the instruction being looked at may be wrapped by another instruction such
as a sign-extend.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">For example:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">%19 = load i64, i64* %LOOPN28, align 8, !tbaa !25<o:p></o:p></p>
<p class="MsoNormal">%conv267 = and i64 %19, 65535 //taking lower 16 bits<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">%24 = trunc i64 %19 to i32<o:p></o:p></p>
<p class="MsoNormal">%conv38 = and i32 %24, 65535<o:p></o:p></p>
<p class="MsoNormal">%sub277 = add nsw i32 %conv38, -1<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Suppose I am currently analyzing %sub277’s operand, %conv38.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Is there a way to simplify expressions such that it would be easier to determine that %conv38 and %conv267 both are ‘coming’ from %19 but just truncated / sign extended?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have looked into the PatternMatch API, but it seems like the limitations of it would still result in having to know the sequence of sign-extension/truncation operations before hand.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have also looked into potentially using ScalarEvolution to get the SCEV and traverse the subexpressions, but again that would rely on knowing the possible list of patterns before hand.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Is there a more generic approach to tackling this problem?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal">Wilson<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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