[llvm] [msan] Handle NEON vector load (PR #130457)

[Florian Mayer via llvm-commits]

================
@@ -4242,6 +4241,80 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     setOriginForNaryOp(I);
   }
 
+  // Handle Arm NEON vector load intrinsics (vld*).
+  //
+  // The WithLane instructions (ld[234]lane) are similar to:
+  //     call {<4 x i32>, <4 x i32>, <4 x i32>}
+  //          @llvm.aarch64.neon.ld3lane.v4i32.p0
+  //              (<4 x i32> %L1, <4 x i32> %L2, <4 x i32> %L3, i64 %lane, ptr
+  //              %A)
+  //
+  // The non-WithLane instructions (ld[234], ld1x[234], ld[234]r) are similar
+  // to:
+  //     call {<8 x i8>, <8 x i8>} @llvm.aarch64.neon.ld2.v8i8.p0(ptr %A)
+  void handleNEONVectorLoad(IntrinsicInst &I, bool WithLane) {
+    unsigned int numArgs = I.arg_size();
+
+    // Return type is a struct of vectors of integers or floating-point
+    assert(I.getType()->isStructTy());
+    [[maybe_unused]] StructType *RetTy = cast<StructType>(I.getType());
+    assert(RetTy->getNumElements() > 0);
+    assert(RetTy->getElementType(0)->isIntOrIntVectorTy() ||
+           RetTy->getElementType(0)->isFPOrFPVectorTy());
+    for (unsigned int i = 0; i < RetTy->getNumElements(); i++)
+      assert(RetTy->getElementType(i) == RetTy->getElementType(0));
+
+    if (WithLane) {
+      // 2, 3 or 4 vectors, plus lane number, plus input pointer
+      assert(4 <= numArgs && numArgs <= 6);
+
+      // Return type is a struct of the input vectors
+      assert(RetTy->getNumElements() + 2 == numArgs);
+      for (unsigned int i = 0; i < RetTy->getNumElements(); i++)
+        assert(I.getArgOperand(i)->getType() == RetTy->getElementType(0));
+    } else {
+      assert(numArgs == 1);
+    }
+
+    IRBuilder<> IRB(&I);
+
+    SmallVector<Value *, 6> ShadowArgs;
+    if (WithLane) {
+      for (unsigned int i = 0; i < numArgs - 2; i++)
+        ShadowArgs.push_back(getShadow(I.getArgOperand(i)));
+
+      // Lane number, passed verbatim
+      Value *LaneNumber = I.getArgOperand(numArgs - 2);
+      ShadowArgs.push_back(LaneNumber);
+
+      // TODO: blend shadow of lane number into output shadow?
+      insertShadowCheck(LaneNumber, &I);
+    }
+
+    Value *Src = I.getArgOperand(numArgs - 1);
+    assert(Src->getType()->isPointerTy() && "Source is not a pointer!");
+
+    const Align Alignment = Align(1);
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fmayer wrote:

Why don't we just pass `Align(1)` below?

https://github.com/llvm/llvm-project/pull/130457