From 1c59eed83a49e9b30fc36c86fc104dd9ceccfee8 Mon Sep 17 00:00:00 2001
From: Alexey Prokhin <alexey.prokhin@yandex.ru>
Date: Mon, 3 Jan 2011 16:50:08 +0300
Subject: [PATCH] Check for lower slice bound when bounds checking is enabled

---
 gen/arrays.cpp | 35 ++++++++++++++++++++++++++++++-----
 gen/arrays.h   |  2 +-
 gen/toir.cpp   | 10 +++++++---
 3 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/gen/arrays.cpp b/gen/arrays.cpp
index 9d9449be..c4de5dd2 100644
--- a/gen/arrays.cpp
+++ b/gen/arrays.cpp
@@ -1274,7 +1274,7 @@ DValue* DtoCastArray(Loc& loc, DValue* u, Type* to)
         else {
             size_t i = (tosize * totype->nextOf()->size() - 1) / fromtype->nextOf()->size();
             DConstValue index(Type::tsize_t, DtoConstSize_t(i));
-            DtoArrayBoundsCheck(loc, u, &index, false);
+            DtoArrayBoundsCheck(loc, u, &index);
 
             rval = DtoArrayPtr(u);
             rval = DtoBitCast(rval, getPtrToType(tolltype));
@@ -1302,24 +1302,49 @@ DValue* DtoCastArray(Loc& loc, DValue* u, Type* to)
 }
 
 //////////////////////////////////////////////////////////////////////////////////////////
-void DtoArrayBoundsCheck(Loc& loc, DValue* arr, DValue* index, bool isslice)
+void DtoArrayBoundsCheck(Loc& loc, DValue* arr, DValue* index, DValue* lowerBound)
 {
     Type* arrty = arr->getType()->toBasetype();
+#if DMDV2
+    assert((arrty->ty == Tsarray || arrty->ty == Tarray || arrty->ty == Tpointer) &&
+        "Can only array bounds check for static or dynamic arrays");
+#else
     assert((arrty->ty == Tsarray || arrty->ty == Tarray) &&
         "Can only array bounds check for static or dynamic arrays");
+#endif
 
     // static arrays could get static checks for static indices
     // but shouldn't since it might be generic code that's never executed
 
     // runtime check
 
+    bool lengthUnknown = arrty->ty == Tpointer;
+
     llvm::BasicBlock* oldend = gIR->scopeend();
     llvm::BasicBlock* failbb = llvm::BasicBlock::Create(gIR->context(), "arrayboundscheckfail", gIR->topfunc(), oldend);
     llvm::BasicBlock* okbb = llvm::BasicBlock::Create(gIR->context(), "arrayboundsok", gIR->topfunc(), oldend);
+    LLValue* cond = 0;
 
-    llvm::ICmpInst::Predicate cmpop = isslice ? llvm::ICmpInst::ICMP_ULE : llvm::ICmpInst::ICMP_ULT;
-    LLValue* cond = gIR->ir->CreateICmp(cmpop, index->getRVal(), DtoArrayLen(arr), "boundscheck");
-    gIR->ir->CreateCondBr(cond, okbb, failbb);
+    if (!lengthUnknown) {
+        // if lowerBound is not NULL, we're checking slice
+        llvm::ICmpInst::Predicate cmpop = lowerBound ? llvm::ICmpInst::ICMP_ULE : llvm::ICmpInst::ICMP_ULT;
+        // check for upper bound
+        cond = gIR->ir->CreateICmp(cmpop, index->getRVal(), DtoArrayLen(arr), "boundscheck");
+    }
+
+    if (!lowerBound) {
+        assert(cond);
+        gIR->ir->CreateCondBr(cond, okbb, failbb);
+    } else {
+        if (!lengthUnknown) {
+            llvm::BasicBlock* locheckbb = llvm::BasicBlock::Create(gIR->context(), "arrayboundschecklowerbound", gIR->topfunc(), oldend);
+            gIR->ir->CreateCondBr(cond, locheckbb, failbb);
+            gIR->scope() = IRScope(locheckbb, failbb);
+        }
+        // check for lower bound
+        cond = gIR->ir->CreateICmp(llvm::ICmpInst::ICMP_ULE, lowerBound->getRVal(), index->getRVal(), "boundscheck");
+        gIR->ir->CreateCondBr(cond, okbb, failbb);
+    }
 
     // set up failbb to call the array bounds error runtime function
 
diff --git a/gen/arrays.h b/gen/arrays.h
index e61a7d5d..93c955d7 100644
--- a/gen/arrays.h
+++ b/gen/arrays.h
@@ -51,6 +51,6 @@ LLValue* DtoArrayPtr(DValue* v);
 DValue* DtoCastArray(Loc& loc, DValue* val, Type* to);
 
 // generates an array bounds check
-void DtoArrayBoundsCheck(Loc& loc, DValue* arr, DValue* index, bool isslice);
+void DtoArrayBoundsCheck(Loc& loc, DValue* arr, DValue* index, DValue* lowerBound = 0);
 
 #endif // LLVMC_GEN_ARRAYS_H
diff --git a/gen/toir.cpp b/gen/toir.cpp
index 1dbbb563..fe6b4938 100644
--- a/gen/toir.cpp
+++ b/gen/toir.cpp
@@ -1268,7 +1268,7 @@ DValue* IndexExp::toElem(IRState* p)
     }
     else if (e1type->ty == Tsarray) {
         if(global.params.useArrayBounds)
-            DtoArrayBoundsCheck(loc, l, r, false);
+            DtoArrayBoundsCheck(loc, l, r);
         arrptr = DtoGEP(l->getRVal(), zero, r->getRVal());
     }
     else if (e1type->ty == Tarray) {
@@ -1303,7 +1303,7 @@ DValue* IndexExp::toElem(IRState* p)
                 r = new DVarValue(r->getType(), tmp);
             }
 #endif
-            DtoArrayBoundsCheck(loc, l, r, false);
+            DtoArrayBoundsCheck(loc, l, r);
         }
         arrptr = DtoArrayPtr(l);
         arrptr = DtoGEP1(arrptr,r->getRVal());
@@ -1361,8 +1361,12 @@ DValue* SliceExp::toElem(IRState* p)
         LLValue* vlo = lo->getRVal();
         LLValue* vup = up->getRVal();
 
+#if DMDV2
+        if(global.params.useArrayBounds)
+#else
         if(global.params.useArrayBounds && (etype->ty == Tsarray || etype->ty == Tarray))
-            DtoArrayBoundsCheck(loc, e, up, true);
+#endif
+            DtoArrayBoundsCheck(loc, e, up, lo);
 
         // offset by lower
         eptr = DtoGEP1(eptr, vlo);