IR: Don't constant fold GEP bitcasts between different address spaces

PR15262 reported a bug where the following instruction: i8 getelementptr inbounds i8* bitcast ([4 x i8] addrspace(12)* @buf to i8*), i32 2 was getting folded into: addrspace(12)* getelementptr inbounds ([4 x i8] addrspace(12)* @buf, i32 0, i32 2) This caused instcombine to crash because the original instruction and the folded instruction have different types. The issue was fixed by disallowing bitcasts between different address spaces to be folded away. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176156 91177308-0d34-0410-b5e6-96231b3b80d8
hacxman · Feb 27, 2013 · 8df7c39 · 8df7c39
1 parent 5e5974f
commit 8df7c39
Show file tree

Hide file tree

Showing 2 changed files with 42 additions and 13 deletions.
diff --git a/lib/IR/ConstantFold.cpp b/lib/IR/ConstantFold.cpp
@@ -1971,21 +1971,30 @@ static Constant *ConstantFoldGetElementPtrImpl(Constant *C,
       }
     }
 
-    // Implement folding of:
-    //    i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*),
-    //                        i64 0, i64 0)
-    // To: i32* getelementptr ([3 x i32]* %X, i64 0, i64 0)
+    // Attempt to fold casts to the same type away.  For example, folding:
     //
+    //   i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*),
+    //                       i64 0, i64 0)
+    // into:
+    //
+    //   i32* getelementptr ([3 x i32]* %X, i64 0, i64 0)
+    //
+    // Don't fold if the cast is changing address spaces.
     if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) {
-      if (PointerType *SPT =
-          dyn_cast<PointerType>(CE->getOperand(0)->getType()))
-        if (ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
-          if (ArrayType *CAT =
-        dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
-            if (CAT->getElementType() == SAT->getElementType())
-              return
-                ConstantExpr::getGetElementPtr((Constant*)CE->getOperand(0),
-                                               Idxs, inBounds);
+      PointerType *SrcPtrTy =
+        dyn_cast<PointerType>(CE->getOperand(0)->getType());
+      PointerType *DstPtrTy = dyn_cast<PointerType>(CE->getType());
+      if (SrcPtrTy && DstPtrTy) {
+        ArrayType *SrcArrayTy =
+          dyn_cast<ArrayType>(SrcPtrTy->getElementType());
+        ArrayType *DstArrayTy =
+          dyn_cast<ArrayType>(DstPtrTy->getElementType());
+        if (SrcArrayTy && DstArrayTy
+            && SrcArrayTy->getElementType() == DstArrayTy->getElementType()
+            && SrcPtrTy->getAddressSpace() == DstPtrTy->getAddressSpace())
+          return ConstantExpr::getGetElementPtr((Constant*)CE->getOperand(0),
+                                                Idxs, inBounds);
+      }
     }
   }
 

diff --git a/test/Other/constant-fold-gep.ll b/test/Other/constant-fold-gep.ll
@@ -447,4 +447,24 @@ define i32* @fZ() nounwind {
   ret i32* %t
 }
 
+; PR15262 - Check GEP folding with casts between address spaces.
+
+@p0 = global [4 x i8] zeroinitializer, align 1
+@p12 = addrspace(12) global [4 x i8] zeroinitializer, align 1
+
+define i8* @different_addrspace() nounwind noinline {
+; OPT: different_addrspace
+  %p = getelementptr inbounds i8* bitcast ([4 x i8] addrspace(12)* @p12 to i8*),
+                                  i32 2
+  ret i8* %p
+; OPT: ret i8* getelementptr (i8* bitcast ([4 x i8] addrspace(12)* @p12 to i8*), i32 2)
+}
+
+define i8* @same_addrspace() nounwind noinline {
+; OPT: same_addrspace
+  %p = getelementptr inbounds i8* bitcast ([4 x i8] * @p0 to i8*), i32 2
+  ret i8* %p
+; OPT: ret i8* getelementptr inbounds ([4 x i8]* @p0, i32 0, i32 2)
+}
+
 ; CHECK: attributes #0 = { nounwind }