use CPU flag instead of thread local storage for the error indicator; progress

compiler/ccgstmts.nim

@@ -731,9 +731,9 @@ proc raiseExit(p: BProc) =
     if p.nestedTryStmts.len == 0:
       p.flags.incl beforeRetNeeded
       # easy case, simply goto 'ret':
-      lineCg(p, cpsStmts, "if (NIM_UNLIKELY(*nimErr_)) goto BeforeRet_;$n", [])
+      lineCg(p, cpsStmts, "NIM_ERR_JUMP(BeforeRet_);$n", [])
     else:
-      lineCg(p, cpsStmts, "if (NIM_UNLIKELY(*nimErr_)) goto LA$1_;$n",
+      lineCg(p, cpsStmts, "NIM_ERR_JUMP(LA$1_);$n",
         [p.nestedTryStmts[^1].label])
 
 proc finallyActions(p: BProc) =
@@ -1282,8 +1282,14 @@ proc genTryGoto(p: BProc; t: PNode; d: var TLoc) =
 
   expr(p, t[0], d)
 
+  var endLabel = -1
   if 1 < t.len and t[1].kind == nkExceptBranch:
-    startBlock(p, "if (NIM_UNLIKELY(*nimErr_)) {$n")
+    inc p.labels
+    endLabel = p.labels
+    #startBlock(p, "if (NIM_UNLIKELY(*nimErr_)) {$n")
+    linefmt(p, cpsStmts, "NIM_ERR_JUMP(LA$1_);$n", [lab])
+    linefmt(p, cpsStmts, "goto LA$1_;$n", [endLabel])
+    startBlock(p, "if (NIM_TRUE) {$n") # so that the `else` works out
   else:
     startBlock(p)
   linefmt(p, cpsStmts, "LA$1_:;$n", [lab])
@@ -1303,7 +1309,7 @@ proc genTryGoto(p: BProc; t: PNode; d: var TLoc) =
       if i > 1: lineF(p, cpsStmts, "else", [])
       startBlock(p)
       # we handled the exception, remember this:
-      linefmt(p, cpsStmts, "*nimErr_ = NIM_FALSE;$n", [])
+      linefmt(p, cpsStmts, "NIM_ERR_CLEAR();$n", [])
       expr(p, t[i][0], d)
     else:
       var orExpr = newRopeAppender()
@@ -1322,7 +1328,7 @@ proc genTryGoto(p: BProc; t: PNode; d: var TLoc) =
       if i > 1: line(p, cpsStmts, "else ")
       startBlock(p, "if ($1) {$n", [orExpr])
       # we handled the exception, remember this:
-      linefmt(p, cpsStmts, "*nimErr_ = NIM_FALSE;$n", [])
+      linefmt(p, cpsStmts, "NIM_ERR_CLEAR();$n", [])
       expr(p, t[i][^1], d)
 
     linefmt(p, cpsStmts, "#popCurrentException();$n", [])
@@ -1332,6 +1338,8 @@ proc genTryGoto(p: BProc; t: PNode; d: var TLoc) =
     inc(i)
   discard pop(p.nestedTryStmts)
   endBlock(p)
+  if endLabel >= 0:
+    linefmt(p, cpsStmts, "LA$1_:;$n", [endLabel])
 
   if i < t.len and t[i].kind == nkFinally:
     startBlock(p)
@@ -1342,7 +1350,17 @@ proc genTryGoto(p: BProc; t: PNode; d: var TLoc) =
     else:
       # pretend we did handle the error for the safe execution of the 'finally' section:
       p.procSec(cpsLocals).add(ropecg(p.module, "NIM_BOOL oldNimErrFin$1_;$n", [lab]))
-      linefmt(p, cpsStmts, "oldNimErrFin$1_ = *nimErr_; *nimErr_ = NIM_FALSE;$n", [lab])
+
+      inc p.labels, 2
+      let fLabel = p.labels-1
+      let tLabel = p.labels
+
+      linefmt(p, cpsStmts, "NIM_ERR_JUMP(LA$1_);$n", [tLabel])
+      linefmt(p, cpsStmts, "oldNimErrFin$1_ = NIM_FALSE; goto LA$2_;$n", [lab, fLabel])
+      linefmt(p, cpsStmts, "LA$2_: oldNimErrFin$1_ = NIM_TRUE; LA$3_: ;$n", [lab, tLabel, fLabel])
+      linefmt(p, cpsStmts, "NIM_ERR_CLEAR();$n", [])
+
+      #linefmt(p, cpsStmts, "oldNimErrFin$1_ = *nimErr_; NIM_ERR_CLEAR();$n", [lab])
       genStmts(p, t[i][0])
       # this is correct for all these cases:
       # 1. finally is run during ordinary control flow
@@ -1350,7 +1368,7 @@ proc genTryGoto(p: BProc; t: PNode; d: var TLoc) =
       #    error back to nil.
       # 3. finally is run for exception handling code without any 'except'
       #    handler present or only handlers that did not match.
-      linefmt(p, cpsStmts, "*nimErr_ = oldNimErrFin$1_;$n", [lab])
+      linefmt(p, cpsStmts, "if (oldNimErrFin$1_) { NIM_ERR_SET(); } else { NIM_ERR_CLEAR(); }$n", [lab])
     endBlock(p)
   raiseExit(p)
   if hasExcept: inc p.withinTryWithExcept

compiler/cgen.nim

@@ -1172,8 +1172,9 @@ proc genProcBody(p: BProc; procBody: PNode) =
   genStmts(p, procBody) # modifies p.locals, p.init, etc.
   if {nimErrorFlagAccessed, nimErrorFlagDeclared, nimErrorFlagDisabled} * p.flags == {nimErrorFlagAccessed}:
     p.flags.incl nimErrorFlagDeclared
-    p.blocks[0].sections[cpsLocals].add(ropecg(p.module, "NIM_BOOL* nimErr_;$n", []))
-    p.blocks[0].sections[cpsInit].add(ropecg(p.module, "nimErr_ = #nimErrorFlag();$n", []))
+    p.blocks[0].sections[cpsLocals].add(ropecg(p.module, "NIM_ERR_FLAG();$n", []))
+    if not isDefined(p.config, "nimUseCpuFlag"):
+      p.blocks[0].sections[cpsInit].add(ropecg(p.module, "nimErr_ = #nimErrorFlag();$n", []))
 
 proc isNoReturn(m: BModule; s: PSym): bool {.inline.} =
   sfNoReturn in s.flags and m.config.exc != excGoto
@@ -1459,6 +1460,9 @@ proc addNimDefines(result: var Rope; conf: ConfigRef) {.inline.} =
   if conf.isDefined("nimEmulateOverflowChecks"):
     result.add("#define NIM_EmulateOverflowChecks\L")
 
+  if conf.isDefined("nimUseCpuFlag"):
+    result.add("#define NIM_UseCpuFlag\L")
+
 proc headerTop(): Rope =
   result = "/* Generated by Nim Compiler v$1 */$N" % [rope(VersionAsString)]
 

lib/nimbase.h

@@ -594,25 +594,28 @@ NIM_STATIC_ASSERT(sizeof(NI) == sizeof(void*) && NIM_INTBITS == sizeof(NI)*8, "P
 #define NIM_NOALIAS __restrict
 /* __restrict is said to work for all the C(++) compilers out there that we support */
 
-#if defined(__GNUC__)
-#  define NIM_ERR_FLAG()  /* nothing to declare: uses HW flag */
-#  define NIM_ERR_JUMP(lab)  __asm__ goto("jc %l0" \
+#if defined(NIM_UseCpuFlag)
+#  if defined(__x86_64__) || defined(__i386__)
+#    define NIM_ERR_FLAG()  /* nothing to declare: uses HW flag */
+#    define NIM_ERR_JUMP(lab)  __asm__ goto("jc %l0" \
                : \
                : \
                : \
                : lab)
-#  define NIM_ERR_SET()   __asm__ volatile("stc" \
+#    define NIM_ERR_SET()   __asm__ volatile("stc" \
     : \
     : \
     : "cc" \
     )
 
-#  define NIM_ERR_CLEAR() __asm__ volatile("clc" \
+#    define NIM_ERR_CLEAR() __asm__ volatile("clc" \
     : \
     : \
     : "cc" \
     )
-
+#  else
+#    error "CPU flags not implemented for your platform"
+#  endif
 #else
 #  define NIM_ERR_FLAG()  NIM_BOOL* nimErr_
 #  define NIM_ERR_JUMP(lab) if (NIM_UNLIKELY(*nimErr_)) goto lab

lib/system/excpt.nim

@@ -472,7 +472,7 @@ proc raiseExceptionAux(e: sink(ref Exception)) {.nodestroy.} =
   elif quirkyExceptions or gotoBasedExceptions:
     pushCurrentException(e)
     when gotoBasedExceptions:
-      inc nimInErrorMode
+      nimInErrorMode = true
   else:
     if excHandler != nil:
       pushCurrentException(e)