fixes #22246; generate __builtin_unreachable hints for case defaults (#22350)

* fixes #22246; generate `__builtin_unreachable` hints

* use elif

* indentation

* fixes holy enums in sim

compiler/ccgstmts.nim

@@ -971,8 +971,11 @@ proc genOrdinalCase(p: BProc, n: PNode, d: var TLoc) =
         hasDefault = true
       exprBlock(p, branch.lastSon, d)
       lineF(p, cpsStmts, "break;$n", [])
-    if (hasAssume in CC[p.config.cCompiler].props) and not hasDefault:
-      lineF(p, cpsStmts, "default: __assume(0);$n", [])
+    if not hasDefault:
+      if hasBuiltinUnreachable in CC[p.config.cCompiler].props:
+        lineF(p, cpsStmts, "default: __builtin_unreachable();$n", [])
+      elif hasAssume in CC[p.config.cCompiler].props:
+        lineF(p, cpsStmts, "default: __assume(0);$n", [])
     lineF(p, cpsStmts, "}$n", [])
   if lend != "": fixLabel(p, lend)
 

compiler/extccomp.nim

@@ -33,6 +33,7 @@ type
     hasGnuAsm,                # CC's asm uses the absurd GNU assembler syntax
     hasDeclspec,              # CC has __declspec(X)
     hasAttribute,             # CC has __attribute__((X))
+    hasBuiltinUnreachable     # CC has __builtin_unreachable
   TInfoCCProps* = set[TInfoCCProp]
   TInfoCC* = tuple[
     name: string,        # the short name of the compiler
@@ -95,7 +96,7 @@ compiler gcc:
     produceAsm: gnuAsmListing,
     cppXsupport: "-std=gnu++17 -funsigned-char",
     props: {hasSwitchRange, hasComputedGoto, hasCpp, hasGcGuard, hasGnuAsm,
-            hasAttribute})
+            hasAttribute, hasBuiltinUnreachable})
 
 # GNU C and C++ Compiler
 compiler nintendoSwitchGCC:
@@ -122,7 +123,7 @@ compiler nintendoSwitchGCC:
     produceAsm: gnuAsmListing,
     cppXsupport: "-std=gnu++17 -funsigned-char",
     props: {hasSwitchRange, hasComputedGoto, hasCpp, hasGcGuard, hasGnuAsm,
-            hasAttribute})
+            hasAttribute, hasBuiltinUnreachable})
 
 # LLVM Frontend for GCC/G++
 compiler llvmGcc:

testament/important_packages.nim

@@ -146,7 +146,7 @@ pkg "rosencrantz", "nim c -o:rsncntz -r rosencrantz.nim"
 pkg "sdl1", "nim c -r src/sdl.nim"
 pkg "sdl2_nim", "nim c -r sdl2/sdl.nim"
 pkg "sigv4", "nim c --gc:arc -r sigv4.nim", "https://github.com/disruptek/sigv4"
-pkg "sim"
+pkg "sim", url = "https://github.com/nim-lang/sim.nim"
 pkg "smtp", "nimble compileExample"
 pkg "snip", "nimble test", "https://github.com/genotrance/snip"
 pkg "ssostrings"