[NFC][MSAN] Extract llvm.abs handling into a function

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D88519

Author: vitalybuka

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

@@ -2638,12 +2638,6 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
       return false;
 
     unsigned NumArgOperands = I.getNumArgOperands();
-    if (I.getIntrinsicID() == Intrinsic::abs) {
-      assert(NumArgOperands == 2);
-      // The last argument is just a boolean flag.
-      NumArgOperands = 1;
-    }
-
     for (unsigned i = 0; i < NumArgOperands; ++i) {
       Type *Ty = I.getArgOperand(i)->getType();
       if (Ty != RetTy)
@@ -3236,8 +3230,24 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     setOriginForNaryOp(I);
   }
 
+  // Instrument abs intrinsic.
+  // handleUnknownIntrinsic can't handle it because of the last
+  // is_int_min_poison argument which does not match the result type.
+  void handleAbsIntrinsic(IntrinsicInst &I) {
+    assert(I.getType()->isIntOrIntVectorTy());
+    assert(I.getArgOperand(0)->getType() == I.getType());
+
+    // FIXME: Handle is_int_min_poison.
+    IRBuilder<> IRB(&I);
+    setShadow(&I, getShadow(&I, 0));
+    setOrigin(&I, getOrigin(&I, 0));
+  }
+
   void visitIntrinsicInst(IntrinsicInst &I) {
     switch (I.getIntrinsicID()) {
+    case Intrinsic::abs:
+      handleAbsIntrinsic(I);
+      break;
     case Intrinsic::lifetime_start:
       handleLifetimeStart(I);
       break;