Add constant support to object size handling and remove default

[oota-llvm.git] / lib / Transforms / InstCombine / InstCombineCalls.cpp

diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 47c37c46587d4fd0634154fcf7c5d06c770bbad1..f06cd12ffce57faf7fb1ca8533dcc4e97bbdd3cd 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -633,16 +633,42 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
     break;
   }
   case Intrinsic::objectsize: {
-    ConstantInt *Const = cast<ConstantInt>(II->getOperand(2));
-    const Type *Ty = CI.getType();
-
-    // 0 is maximum number of bytes left, 1 is minimum number of bytes left.
-    // TODO: actually add these values, the current return values are "don't
-    // know".
-    if (Const->getZExtValue() == 0)
-      return ReplaceInstUsesWith(CI, Constant::getAllOnesValue(Ty));
-    else
-      return ReplaceInstUsesWith(CI, ConstantInt::get(Ty, 0));
+    const Type *ReturnTy = CI.getType();
+    Value *Op1 = II->getOperand(1);
+    
+    // If we're a constant expr then we just return the number of bytes
+    // left in whatever we're indexing.  Since it's constant there's no
+    // need for maximum or minimum bytes.
+    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op1)) {
+      // If this isn't a GEP give up.
+      if (CE->getOpcode() != Instruction::GetElementPtr) return 0;
+      
+      const PointerType *ObjTy = 
+        reinterpret_cast<const PointerType*>(CE->getOperand(0)->getType());
+
+      if (const ArrayType *AT = dyn_cast<ArrayType>(ObjTy->getElementType())) {
+        
+        // Deal with multi-dimensional arrays
+        const ArrayType *SAT = AT;
+        while ((AT = dyn_cast<ArrayType>(AT->getElementType())))
+          SAT = AT;
+        
+        size_t numElems = SAT->getNumElements();
+        // We return the remaining bytes, so grab the size of an element
+        // in bytes.
+        size_t sizeofElem = SAT->getElementType()->getPrimitiveSizeInBits() / 8;
+
+        ConstantInt *Const = 
+          cast<ConstantInt>(CE->getOperand(CE->getNumOperands() - 1));
+        size_t indx = Const->getZExtValue();
+        return ReplaceInstUsesWith(CI,
+                      ConstantInt::get(ReturnTy,
+                                       ((numElems - indx) * sizeofElem)));
+      }
+    }
+
+    // TODO: Add more Instruction types here.
+    
   }
   }