VM can now cast integer type arbitrarily. (#11459) [feature]

1 files changed, 15 insertions, 31 deletions

diff --git a/compiler/vmgen.nim b/compiler/vmgen.nim
index 035ab25cd..de314a552 100644
--- a/compiler/vmgen.nim
+++ b/compiler/vmgen.nim
@@ -813,44 +813,28 @@ proc genCard(c: PCtx; n: PNode; dest: var TDest) =
 
 proc genCastIntFloat(c: PCtx; n: PNode; dest: var TDest) =
   const allowedIntegers = {tyInt..tyInt64, tyUInt..tyUInt64, tyChar}
-  var signedIntegers = {tyInt8..tyInt32}
-  var unsignedIntegers = {tyUInt8..tyUInt32, tyChar}
+  var signedIntegers = {tyInt..tyInt64}
+  var unsignedIntegers = {tyUInt..tyUInt64, tyChar}
   let src = n.sons[1].typ.skipTypes(abstractRange)#.kind
   let dst = n.sons[0].typ.skipTypes(abstractRange)#.kind
   let src_size = getSize(c.config, src)
   let dst_size = getSize(c.config, dst)
-  if c.config.target.intSize < 8:
-    signedIntegers.incl(tyInt)
-    unsignedIntegers.incl(tyUInt)
-  if src_size == dst_size and src.kind in allowedIntegers and
-                                 dst.kind in allowedIntegers:
+  if src.kind in allowedIntegers and dst.kind in allowedIntegers:
     let tmp = c.genx(n.sons[1])
-    var tmp2 = c.getTemp(n.sons[1].typ)
-    let tmp3 = c.getTemp(n.sons[1].typ)
     if dest < 0: dest = c.getTemp(n[0].typ)
-    proc mkIntLit(ival: int): int =
-      result = genLiteral(c, newIntTypeNode(nkIntLit, ival, getSysType(c.graph, n.info, tyInt)))
-    if src.kind in unsignedIntegers and dst.kind in signedIntegers:
-      # cast unsigned to signed integer of same size
-      # signedVal = (unsignedVal xor offset) -% offset
-      let offset = 1 shl (src_size * 8 - 1)
-      c.gABx(n, opcLdConst, tmp2, mkIntLit(offset))
-      c.gABC(n, opcBitxorInt, tmp3, tmp, tmp2)
-      c.gABC(n, opcSubInt, dest, tmp3, tmp2)
-    elif src.kind in signedIntegers and dst.kind in unsignedIntegers:
-      # cast signed to unsigned integer of same size
-      # unsignedVal = (offset +% signedVal +% 1) and offset
-      let offset = (1 shl (src_size * 8)) - 1
-      c.gABx(n, opcLdConst, tmp2, mkIntLit(offset))
-      c.gABx(n, opcLdConst, dest, mkIntLit(offset+1))
-      c.gABC(n, opcAddu, tmp3, tmp, dest)
-      c.gABC(n, opcNarrowU, tmp3, TRegister(src_size*8))
-      c.gABC(n, opcBitandInt, dest, tmp3, tmp2)
-    else:
-      c.gABC(n, opcAsgnInt, dest, tmp)
+    c.gABC(n, opcAsgnInt, dest, tmp)
+    if dst_size != sizeof(BiggestInt): # don't do anything on biggest int types
+      if dst.kind in signedIntegers: # we need to do sign extensions
+        if dst_size <= src_size:
+          # Sign extension can be omitted when the size increases.
+          c.gABC(n, opcSignExtend, dest, TRegister(dst_size*8))
+      elif dst.kind in unsignedIntegers:
+        if src.kind in signedIntegers or dst_size < src_size:
+          # Cast from signed to unsigned always needs narrowing. Cast
+          # from unsigned to unsigned only needs narrowing when target
+          # is smaller than source.
+          c.gABC(n, opcNarrowU, dest, TRegister(dst_size*8))
     c.freeTemp(tmp)
-    c.freeTemp(tmp2)
-    c.freeTemp(tmp3)
   elif src_size == dst_size and src.kind in allowedIntegers and
                            dst.kind in {tyFloat, tyFloat32, tyFloat64}:
     let tmp = c.genx(n[1])