Add constant support to object size handling and remove default

lowering. We'll either figure it out, or not and be lowered by
SelectionDAGBuild.

Add test.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94775 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 66 insertions, 10 deletions

diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 47c37c4658..f06cd12ffc 100644
--- 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.
+    
   }
   }
 
diff --git a/test/Transforms/InstCombine/objsize.ll b/test/Transforms/InstCombine/objsize.ll
new file mode 100644
index 0000000000..13bb487c13
--- /dev/null
+++ b/test/Transforms/InstCombine/objsize.ll
@@ -0,0 +1,30 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+@a = common global [60 x i8] zeroinitializer, align 1 ; <[60 x i8]*>
+@.str = private constant [8 x i8] c"abcdefg\00"   ; <[8 x i8]*>
+
+define i32 @foo() nounwind {
+; CHECK: @foo
+; CHECK-NEXT: ret i32 60
+  %1 = call i32 @llvm.objectsize.i32(i8* getelementptr inbounds ([60 x i8]* @a, i32 0, i32 0), i1 false)
+  ret i32 %1
+}
+
+define i8* @bar() nounwind {
+; CHECK: @bar
+entry:
+  %retval = alloca i8*
+  %0 = call i32 @llvm.objectsize.i32(i8* getelementptr inbounds ([60 x i8]* @a, i32 0, i32 0), i1 false)
+  %cmp = icmp ne i32 %0, -1
+; CHECK: br i1 true
+  br i1 %cmp, label %cond.true, label %cond.false
+
+cond.true:
+  %1 = load i8** %retval;
+  ret i8* %1;
+
+cond.false:
+  %2 = load i8** %retval;
+  ret i8* %2;
+}
+
+declare i32 @llvm.objectsize.i32(i8*, i1) nounwind readonly
\ No newline at end of file