[llvm] [IA][RISCV] Recognizing gap masks assembled from bitwise AND (PR #153324)

[Min-Yih Hsu via llvm-commits]

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@@ -601,6 +602,18 @@ static std::pair<Value *, APInt> getMask(Value *WideMask, unsigned Factor,
     }
   }
 
+  // Try to match `and <interleaved mask>, <gap mask>`. The WideMask here is
+  // expected to be a fixed vector and gap mask should be a constant mask.
+  Value *AndMaskLHS;
+  Constant *AndMaskRHS;
+  if (LeafValueEC.isFixed() &&
+      match(WideMask, m_c_And(m_Value(AndMaskLHS), m_Constant(AndMaskRHS)))) {
+    assert(!isa<Constant>(AndMaskLHS) &&
+           "expect constants to be folded already");
+    getGapMask(*AndMaskRHS, Factor, LeafValueEC.getFixedValue(), GapMask);
+    return {getMask(AndMaskLHS, Factor, LeafValueEC).first, GapMask};
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mshockwave wrote:

> But we cannot write an assert that says it will not happen.

I think that's a fair point. I've updated the patch to make the logics more general: now it will try to merge both the deinterleaved masks and the gap masks from LHS & RHS.

https://github.com/llvm/llvm-project/pull/153324