[PATCH] D47927: [WIP][TargetLowering] Simplify expansion of S{ADD,SUB}O

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri accepted this revision.
lebedev.ri added a comment.
This revision is now accepted and ready to land.

Though the current expansion is just as incorrect for `undef`:

  ----------------------------------------
  Name: sadd
    %t = sadd_overflow i8 %LHS, %RHS
    %v0 = extractvalue {i8, i1} %t, 0
    %v1 = extractvalue {i8, i1} %t, 1
  =>
    %t = sadd_overflow i8 %LHS, %RHS
    %v0 = add i8 %LHS, %RHS
    %LHSSign = icmp sge i8 %LHS, 0
    %RHSSign = icmp sge i8 %RHS, 0
    %SignsMatch = icmp eq i1 %LHSSign, %RHSSign
    %SumSign = icmp sge i8 %v0, 0
    %SumSignNE = icmp ne i1 %LHSSign, %SumSign
    %v1 = and i1 %SignsMatch, %SumSignNE
  
  Done: 1
  Optimization is correct!
  
  ----------------------------------------
  Name: ssub
    %t = ssub_overflow i8 %LHS, %RHS
    %v0 = extractvalue {i8, i1} %t, 0
    %v1 = extractvalue {i8, i1} %t, 1
  =>
    %t = ssub_overflow i8 %LHS, %RHS
    %v0 = sub i8 %LHS, %RHS
    %LHSSign = icmp sge i8 %LHS, 0
    %RHSSign = icmp sge i8 %RHS, 0
    %SignsMatch = icmp ne i1 %LHSSign, %RHSSign
    %SumSign = icmp sge i8 %v0, 0
    %SumSignNE = icmp ne i1 %LHSSign, %SumSign
    %v1 = and i1 %SignsMatch, %SumSignNE
  
  Done: 1
  Optimization is correct!

  ----------------------------------------
  Name: sadd
    %t = sadd_overflow i8 %LHS, %RHS
    %v0 = extractvalue {i8, i1} %t, 0
    %v1 = extractvalue {i8, i1} %t, 1
  =>
    %t = sadd_overflow i8 %LHS, %RHS
    %v0 = add i8 %LHS, %RHS
    %LHSSign = icmp sge i8 %LHS, 0
    %RHSSign = icmp sge i8 %RHS, 0
    %SignsMatch = icmp eq i1 %LHSSign, %RHSSign
    %SumSign = icmp sge i8 %v0, 0
    %SumSignNE = icmp ne i1 %LHSSign, %SumSign
    %v1 = and i1 %SignsMatch, %SumSignNE
  
  ERROR: Value mismatch for i1 %v1
  
  Example:
  i8 %LHS = #x00 (0)
  i8 %RHS = undef
  {i8, i1} %t = { #x00 (0), #x0 (0) }     [based on undef value]
  i8 %v0 = undef
  i1 %LHSSign = #x1 (1)
  i1 %RHSSign = undef
  i1 %SignsMatch = undef
  i1 %SumSign = undef
  i1 %SumSignNE = undef
  Source value: #x0 (0)
  Target value: #x1 (1)
  
  
  ----------------------------------------
  Name: ssub
    %t = ssub_overflow i8 %LHS, %RHS
    %v0 = extractvalue {i8, i1} %t, 0
    %v1 = extractvalue {i8, i1} %t, 1
  =>
    %t = ssub_overflow i8 %LHS, %RHS
    %v0 = sub i8 %LHS, %RHS
    %LHSSign = icmp sge i8 %LHS, 0
    %RHSSign = icmp sge i8 %RHS, 0
    %SignsMatch = icmp ne i1 %LHSSign, %RHSSign
    %SumSign = icmp sge i8 %v0, 0
    %SumSignNE = icmp ne i1 %LHSSign, %SumSign
    %v1 = and i1 %SignsMatch, %SumSignNE
  
  ERROR: Value mismatch for i1 %v1
  
  Example:
  i8 %LHS = undef
  i8 %RHS = #x00 (0)
  {i8, i1} %t = { #x00 (0), #x0 (0) }     [based on undef value]
  i8 %v0 = undef
  i1 %LHSSign = undef
  i1 %RHSSign = #x1 (1)
  i1 %SignsMatch = undef
  i1 %SumSign = undef
  i1 %SumSignNE = undef
  Source value: #x0 (0)
  Target value: #x1 (1)

So LG i guess..


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  https://reviews.llvm.org/D47927/new/

https://reviews.llvm.org/D47927