stage2: implement function call inlining in the frontend

 * remove the -Ddump-zir thing. that's handled through --verbose-ir
 * rework Fn to have an is_inline flag without requiring any more memory
   on the heap per function.
 * implement a rough first version of dumping typed zir (tzir) which is
   a lot more helpful for debugging than what we had before. We don't
   have a way to parse it though.
 * keep track of whether the inline-ness of a function changes because
   if it does we have to go update callsites.
 * add compile error for inline and export used together.

inline function calls and comptime function calls are implemented the
same way. A block instruction is set up to capture the result, and then
a scope is set up that has a flag for is_comptime and some state if the
scope is being inlined.

when analyzing `ret` instructions, zig looks for inlining state in the
scope, and if found, treats `ret` as a `break` instruction instead, with
the target block being the one set up at the inline callsite.

Follow-up items:
 * Complete out the debug TZIR dumping code.
 * Don't redundantly generate ZIR for each inline/comptime function
   call. Instead we should add a new state enum tag to Fn.
 * comptime and inlining branch quotas.
 * Add more test cases.

1 files changed, 9 insertions, 5 deletions

diff --git a/src/Compilation.zig b/src/Compilation.zig
index de115b9b40..a6f39a3154 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -1459,10 +1459,10 @@ pub fn performAllTheWork(self: *Compilation) error{ TimerUnsupported, OutOfMemor
                 const module = self.bin_file.options.module.?;
                 if (decl.typed_value.most_recent.typed_value.val.castTag(.function)) |payload| {
                     const func = payload.data;
-                    switch (func.analysis) {
+                    switch (func.bits.state) {
                         .queued => module.analyzeFnBody(decl, func) catch |err| switch (err) {
                             error.AnalysisFail => {
-                                assert(func.analysis != .in_progress);
+                                assert(func.bits.state != .in_progress);
                                 continue;
                             },
                             error.OutOfMemory => return error.OutOfMemory,
@@ -1471,12 +1471,16 @@ pub fn performAllTheWork(self: *Compilation) error{ TimerUnsupported, OutOfMemor
                         .sema_failure, .dependency_failure => continue,
                         .success => {},
                     }
-                    // Here we tack on additional allocations to the Decl's arena. The allocations are
-                    // lifetime annotations in the ZIR.
+                    // Here we tack on additional allocations to the Decl's arena. The allocations
+                    // are lifetime annotations in the ZIR.
                     var decl_arena = decl.typed_value.most_recent.arena.?.promote(module.gpa);
                     defer decl.typed_value.most_recent.arena.?.* = decl_arena.state;
                     log.debug("analyze liveness of {s}\n", .{decl.name});
-                    try liveness.analyze(module.gpa, &decl_arena.allocator, func.analysis.success);
+                    try liveness.analyze(module.gpa, &decl_arena.allocator, func.data.body);
+
+                    if (self.verbose_ir) {
+                        func.dump(module.*);
+                    }
                 }
 
                 assert(decl.typed_value.most_recent.typed_value.ty.hasCodeGenBits());