[PATCH] D49238: [InstCombine] add more SPFofSPF folding

[Sanjay Patel via Phabricator via llvm-commits]

spatel added inline comments.


================
Comment at: llvm/lib/Analysis/ValueTracking.cpp:4640-4641
     // Set LHS and RHS so that RHS is the negated operand of the select
+    bool CmpUsesNegatedOp = match(CmpLHS, m_Neg(m_Specific(TrueVal))) ||
+                        match(CmpLHS, m_Neg(m_Specific(FalseVal)));
     if (match(TrueVal, MaybeSExtLHS)) {
----------------
What happens if the cmp uses a negated and sign-extended op? I'm not sure if this is possible because of other transforms. Do we have test(s) that include that possibility?


================
Comment at: llvm/test/Transforms/InstCombine/abs_abs.ll:333-336
 ; CHECK-LABEL: @abs_abs_x02_vec(
 ; CHECK-NEXT:    [[SUB:%.*]] = sub nsw <2 x i32> zeroinitializer, [[X:%.*]]
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt <2 x i32> [[SUB]], <i32 -1, i32 -1>
 ; CHECK-NEXT:    [[COND:%.*]] = select <2 x i1> [[CMP]], <2 x i32> [[SUB]], <2 x i32> [[X]]
----------------
Do you know why the scalar version above folded, but the vector version did not? Something is falsely excluding vector types.


https://reviews.llvm.org/D49238