diff options
Diffstat (limited to 'llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp index 0b6b7c3c66d..05a624fde86 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp @@ -704,11 +704,19 @@ static Value *canonicalizeSaturatedSubtract(const ICmpInst *ICI, assert((Pred == ICmpInst::ICMP_UGE || Pred == ICmpInst::ICMP_UGT) && "Unexpected isUnsigned predicate!"); - // Account for swapped form of subtraction: ((a > b) ? b - a : 0). + // Ensure the sub is of the form: + // (a > b) ? a - b : 0 -> usub.sat(a, b) + // (a > b) ? b - a : 0 -> -usub.sat(a, b) + // Checking for both a-b and a+(-b) as a constant. bool IsNegative = false; - if (match(TrueVal, m_Sub(m_Specific(B), m_Specific(A)))) + const APInt *C; + if (match(TrueVal, m_Sub(m_Specific(B), m_Specific(A))) || + (match(A, m_APInt(C)) && + match(TrueVal, m_Add(m_Specific(B), m_SpecificInt(-*C))))) IsNegative = true; - else if (!match(TrueVal, m_Sub(m_Specific(A), m_Specific(B)))) + else if (!match(TrueVal, m_Sub(m_Specific(A), m_Specific(B))) && + !(match(B, m_APInt(C)) && + match(TrueVal, m_Add(m_Specific(A), m_SpecificInt(-*C))))) return nullptr; // If we are adding a negate and the sub and icmp are used anywhere else, we |
