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

[eugenis]

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

2704

Add it to a list in visitIntrinsicInst

[vitalybuka]

use visitIntrinsicInst

[eugenis]

LGTM

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

#endif
   bool maybeHandleSimpleNomemIntrinsic(IntrinsicInst &I) {
     Type *RetTy = I.getType();
     if (!(RetTy->isIntOrIntVectorTy() ||
           RetTy->isFPOrFPVectorTy() ||
           RetTy->isX86_MMXTy()))
       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)
         return false;
     }
 
     IRBuilder<> IRB(&I);
     ShadowAndOriginCombiner SC(this, IRB);
     for (unsigned i = 0; i < NumArgOperands; ++i)
       SC.Add(I.getArgOperand(i));
     SC.Done(&I);
 
     return true;
   }
 
+  bool maybeHandleAbsIntrinsic(IntrinsicInst &I) {
+    if (I.getIntrinsicID() != Intrinsic::abs)
+      return false;
+
+    Type *RetTy = I.getType();
+    assert(RetTy->isIntOrIntVectorTy());
+    assert(I.getArgOperand(0)->getType() == RetTy);
+
+    // FIXME: Handle is_int_min_poison.
+    IRBuilder<> IRB(&I);
+    setShadow(&I, getShadow(&I, 0));
+    setOrigin(&I, getOrigin(&I, 0));
+
+    return true;
+  }
+
   /// Heuristically instrument unknown intrinsics.
   ///
   /// The main purpose of this code is to do something reasonable with all
   /// random intrinsics we might encounter, most importantly - SIMD intrinsics.
   /// We recognize several classes of intrinsics by their argument types and
   /// ModRefBehaviour and apply special instrumentation when we are reasonably
   /// sure that we know what the intrinsic does.
   ///
bool handleUnknownIntrinsic(IntrinsicInst &I) {
     if (NumArgOperands == 1 &&
         I.getArgOperand(0)->getType()->isPointerTy() &&
         I.getType()->isVectorTy() &&
         I.onlyReadsMemory()) {
       // This looks like a vector load.
       return handleVectorLoadIntrinsic(I);
     }
 
+    if (maybeHandleAbsIntrinsic(I))
+      return true;
+
     if (I.doesNotAccessMemory())
       if (maybeHandleSimpleNomemIntrinsic(I))
         return true;
 
     // FIXME: detect and handle SSE maskstore/maskload
     return false;
   }