fixes constant array indexing bug

compiler/semfold.nim

@@ -1,7 +1,7 @@
 #
 #
 #           The Nimrod Compiler
-#        (c) Copyright 2012 Andreas Rumpf
+#        (c) Copyright 2014 Andreas Rumpf
 #
 #    See the file "copying.txt", included in this
 #    distribution, for details about the copyright.
@@ -537,17 +537,18 @@ proc foldArrayAccess(m: PSym, n: PNode): PNode =
   var idx = getOrdValue(y)
   case x.kind
   of nkPar: 
-    if (idx >= 0) and (idx < sonsLen(x)): 
+    if idx >= 0 and idx < sonsLen(x):
       result = x.sons[int(idx)]
       if result.kind == nkExprColonExpr: result = result.sons[1]
     else:
       localError(n.info, errIndexOutOfBounds)
-  of nkBracket: 
-    if (idx >= 0) and (idx < sonsLen(x)): result = x.sons[int(idx)]
+  of nkBracket:
+    idx = idx - x.typ.firstOrd
+    if idx >= 0 and idx < x.len: result = x.sons[int(idx)]
     else: localError(n.info, errIndexOutOfBounds)
-  of nkStrLit..nkTripleStrLit: 
+  of nkStrLit..nkTripleStrLit:
     result = newNodeIT(nkCharLit, x.info, n.typ)
-    if (idx >= 0) and (idx < len(x.strVal)): 
+    if idx >= 0 and idx < len(x.strVal): 
       result.intVal = ord(x.strVal[int(idx)])
     elif idx == len(x.strVal): 
       discard

compiler/vmgen.nim

@@ -84,21 +84,27 @@ proc gABI(c: PCtx; n: PNode; opc: TOpcode; a, b: TRegister; imm: BiggestInt) =
   # Takes the `b` register and the immediate `imm`, appies the operation `opc`,
   # and stores the output value into `a`.
   # `imm` is signed and must be within [-127, 128]
-  assert(imm >= -127 and imm <= 128)
-  let ins = (opc.uint32 or (a.uint32 shl 8'u32) or
-                           (b.uint32 shl 16'u32) or
-                           (imm+byteExcess).uint32 shl 24'u32).TInstr
-  c.code.add(ins)
-  c.debug.add(n.info)
+  if imm >= -127 and imm <= 128:
+    let ins = (opc.uint32 or (a.uint32 shl 8'u32) or
+                             (b.uint32 shl 16'u32) or
+                             (imm+byteExcess).uint32 shl 24'u32).TInstr
+    c.code.add(ins)
+    c.debug.add(n.info)
+  else:
+    localError(n.info, errGenerated,
+      "VM: immediate value does not fit into an int8")
 
 proc gABx(c: PCtx; n: PNode; opc: TOpcode; a: TRegister = 0; bx: int) =
   # Applies `opc` to `bx` and stores it into register `a`
   # `bx` must be signed and in the range [-32767, 32768]
-  assert(bx >= -32767 and bx <= 32768)
-  let ins = (opc.uint32 or a.uint32 shl 8'u32 or 
-            (bx+wordExcess).uint32 shl 16'u32).TInstr
-  c.code.add(ins)
-  c.debug.add(n.info)
+  if bx >= -32767 and bx <= 32768:
+    let ins = (opc.uint32 or a.uint32 shl 8'u32 or 
+              (bx+wordExcess).uint32 shl 16'u32).TInstr
+    c.code.add(ins)
+    c.debug.add(n.info)
+  else:
+    localError(n.info, errGenerated,
+      "VM: immediate value does not fit into an int16")
 
 proc xjmp(c: PCtx; n: PNode; opc: TOpcode; a: TRegister = 0): TPosition =
   #assert opc in {opcJmp, opcFJmp, opcTJmp}
@@ -485,11 +491,22 @@ proc genField(n: PNode): TRegister =
         "too large offset! cannot generate code for: " & s.name.s)
   result = s.position
 
+proc genIndex(c: PCtx; n: PNode; arr: PType): TRegister =
+  if arr.skipTypes(abstractInst).kind == tyArray and (let x = firstOrd(arr);
+      x != 0):
+    let tmp = c.genx(n)
+    # freeing the temporary here means we can produce:  regA = regA - Imm
+    c.freeTemp(tmp)
+    result = c.getTemp(n.typ)
+    c.gABI(n, opcSubImmInt, result, tmp, x.int)
+  else:
+    result = c.genx(n)
+
 proc genAsgnPatch(c: PCtx; le: PNode, value: TRegister) =
   case le.kind
   of nkBracketExpr:
     let dest = c.genx(le.sons[0], {gfAddrOf})
-    let idx = c.genx(le.sons[1])
+    let idx = c.genIndex(le.sons[1], le.sons[0].typ)
     c.gABC(le, opcWrArr, dest, idx, value)
     c.freeTemp(dest)
     c.freeTemp(idx)
@@ -1072,7 +1089,7 @@ proc genAsgn(c: PCtx; le, ri: PNode; requiresCopy: bool) =
   case le.kind
   of nkBracketExpr:
     let dest = c.genx(le.sons[0], {gfAddrOf})
-    let idx = c.genx(le.sons[1])
+    let idx = c.genIndex(le.sons[1], le.sons[0].typ)
     let tmp = c.genx(ri)
     if le.sons[0].typ.skipTypes(abstractVarRange-{tyTypeDesc}).kind in {
         tyString, tyCString}:
@@ -1185,7 +1202,7 @@ proc genRdVar(c: PCtx; n: PNode; dest: var TDest; flags: TGenFlags) =
 proc genArrAccess2(c: PCtx; n: PNode; dest: var TDest; opc: TOpcode;
                    flags: TGenFlags) =
   let a = c.genx(n.sons[0], flags)
-  let b = c.genx(n.sons[1], {})
+  let b = c.genIndex(n.sons[1], n.sons[0].typ)
   if dest < 0: dest = c.getTemp(n.typ)
   if gfAddrOf notin flags and fitsRegister(n.typ):
     var cc = c.getTemp(n.typ)

tests/vm/tarrayboundeval.nim

@@ -1,6 +1,7 @@
 discard """
   output: '''7
-8 8'''
+8 8
+-2'''
 """
 
 #bug 1063
@@ -21,3 +22,10 @@ type
     internal: array[int((KeyMax + 31)/32), cuint]
     
 echo myconst, " ", int((KeyMax + 31) / 32)
+
+#bug 1304 or something:
+
+const constArray: array [-3..2, int] = [-3, -2, -1, 0, 1, 2]
+
+echo constArray[-2]
+