commit 4864173afc93e57ee044f5caba9ebcab1b7b6089
author Cherry Zhang <cherryyz@google.com> Fri Jun 14 10:41:05 2019 -0400
committer Cherry Zhang <cherryyz@google.com> Mon Jun 24 13:57:33 2019 +0000
tree 82f601caa639bc9ea093fddcaa662adf3e36c695
parent a338950300adf998b7f1e6993ef403da8b09e1f7

driver: compile runtime package with nil check removed

Panics in the runtime are uncatchable throws, which will crash
the program anyway. We don't have to worry about if it panics at
the exact memory state as the program order.

With the previous CL, the effect of this CL is allowing the
backend to reorder instructions across a potentially faulting
instruction. The faulting instruction is not removed. So if there
is actually a bug in the runtime causing nil check to fail, it
still crash the program.

Change-Id: Ic87b0fb351be234b3b6727ecb97093257c07a7cf
Reviewed-on: https://go-review.googlesource.com/c/gollvm/+/182579
Reviewed-by: Than McIntosh <thanm@google.com>

driver/CompileGo.cpp

diff --git a/driver/CompileGo.cpp b/driver/CompileGo.cpp
index dc23698..d6c3b8f 100644
--- a/driver/CompileGo.cpp
+++ b/driver/CompileGo.cpp
@@ -685,7 +685,9 @@
       driver_.reconcileOptionPair(gollvm::options::OPT_fgo_debug_optimization,
                                   gollvm::options::OPT_fno_go_debug_optimization,
                                   false);
-  args.nil_check_size_threshold = -1;
+  args.nil_check_size_threshold =
+      (args.compiling_runtime && args.pkgpath && strcmp(args.pkgpath, "runtime") == 0 ?
+       4096 : -1);
   args.linemap = linemap_.get();
   args.backend = bridge_.get();
   go_create_gogo (&args);