[llvm] [IA][RISCV] Support VP loads/stores in InterleavedAccessPass (PR #120490)

[Luke Lau via llvm-commits]

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@@ -22529,6 +22530,233 @@ bool RISCVTargetLowering::lowerInterleaveIntrinsicToStore(
   return true;
 }
 
+static bool isMultipleOfN(const Value *V, const DataLayout &DL, unsigned N) {
+  assert(N);
+  if (N == 1)
+    return true;
+
+  if (isPowerOf2_32(N)) {
+    KnownBits KB = llvm::computeKnownBits(V, DL);
+    return KB.countMinTrailingZeros() >= Log2_32(N);
+  }
+
+  using namespace PatternMatch;
+  // Right now we're only recognizing the simplest pattern.
+  uint64_t C;
+  return match(V, m_c_Mul(m_Value(), m_ConstantInt(C))) && C && C % N == 0;
+}
+
+/// Lower an interleaved vp.load into a vlsegN intrinsic.
+///
+/// E.g. Lower an interleaved vp.load (Factor = 2):
+///   %l = call <vscale x 64 x i8> @llvm.vp.load.nxv64i8.p0(ptr %ptr,
+///                                                         %mask,
+///                                                         i32 %wide.rvl)
+///   %dl = tail call { <vscale x 32 x i8>, <vscale x 32 x i8> }
+///             @llvm.vector.deinterleave2.nxv64i8(
+///               <vscale x 64 x i8> %l)
+///   %r0 = extractvalue { <vscale x 32 x i8>, <vscale x 32 x i8> } %dl, 0
+///   %r1 = extractvalue { <vscale x 32 x i8>, <vscale x 32 x i8> } %dl, 1
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lukel97 wrote:

Nit, should we add the insertvalues into the example here? And maybe leave a TODO to match factor 2 deinterleaves without them?

https://github.com/llvm/llvm-project/pull/120490