[PATCH] D51236: [InstCombine] Extend (add (sext x), cst) --> (sext (add x, cst')) and (add (zext x), cst) --> (zext (add x, cst')) to work for vectors

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


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Comment at: lib/Transforms/InstCombine/InstCombineAddSub.cpp:1199
+    Constant *RHSC;
+    if (match(RHS, m_ConstantIntOrConstantIntVec(RHSC))) {
       if (LHSConv->hasOneUse()) {
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spatel wrote:
> I don't understand what benefit the new pattern matcher offers. We're already guaranteed that the constant is (vector) integer type because this is an 'add'. Do we need to disallow constant expressions? If not, use the existing m_Constant() matcher?
I did it to disallow constant expressions and be better than just using m_APInt. I don't think willNotOverflowSignedAdd will give an answer for constant expressions in general. So we'd just be creating new constant expressions with the call get to ConstantExpr::getTrunc for no reason. And we'd need tests for it.


https://reviews.llvm.org/D51236