Vm bitops fixes (#10520)

compiler/vm.nim

@@ -1264,6 +1264,11 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
     of opcNarrowU:
       decodeB(rkInt)
       regs[ra].intVal = regs[ra].intVal and ((1'i64 shl rb)-1)
+    of opcSignExtend:
+      # like opcNarrowS, but no out of range possible
+      decodeB(rkInt)
+      let imm = 64 - rb
+      regs[ra].intVal = ashr(regs[ra].intVal shl imm, imm)
     of opcIsNil:
       decodeB(rkInt)
       let node = regs[rb].node

compiler/vmdef.nim

@@ -75,6 +75,7 @@ type
     opcSubStr, opcParseFloat, opcConv, opcCast,
     opcQuit,
     opcNarrowS, opcNarrowU,
+    opcSignExtend,
 
     opcAddStrCh,
     opcAddStrStr,

compiler/vmgen.nim

@@ -986,7 +986,14 @@ proc genMagic(c: PCtx; n: PNode; dest: var TDest; m: TMagic) =
     c.freeTemp(tmp)
     c.freeTemp(tmp2)
 
-  of mShlI: genBinaryABCnarrowU(c, n, dest, opcShlInt)
+  of mShlI:
+    genBinaryABC(c, n, dest, opcShlInt)
+    # genNarrowU modified
+    let t = skipTypes(n.typ, abstractVar-{tyTypeDesc})
+    if t.kind in {tyUInt8..tyUInt32} or (t.kind == tyUInt and t.size < 8):
+      c.gABC(n, opcNarrowU, dest, TRegister(t.size*8))
+    elif t.kind in {tyInt8..tyInt32} or (t.kind == tyInt and t.size < 8):
+      c.gABC(n, opcSignExtend, dest, TRegister(t.size*8))
   of mAshrI: genBinaryABC(c, n, dest, opcAshrInt)
   of mBitandI: genBinaryABC(c, n, dest, opcBitandInt)
   of mBitorI: genBinaryABC(c, n, dest, opcBitorInt)