From db296e95939ed856abb564135d2e6f586cf1888e Mon Sep 17 00:00:00 2001
From: Rory OConnell <19547+RoryO@users.noreply.github.com>
Date: Fri, 26 Jun 2020 15:13:04 -0700
Subject: work around MSC optimization generating non functional code

---
 mrbgems/mruby-random/src/random.c | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'mrbgems/mruby-random/src')

diff --git a/mrbgems/mruby-random/src/random.c b/mrbgems/mruby-random/src/random.c
index 515c0707a..6f31b15a6 100644
--- a/mrbgems/mruby-random/src/random.c
+++ b/mrbgems/mruby-random/src/random.c
@@ -210,9 +210,16 @@ random_m_srand(mrb_state *mrb, mrb_value self)
  *  Shuffles elements in self in place.
  */
 
+#if defined _MSC_VER && _MSC_VER >= 1900
+#pragma optimize( "", off )
+#endif
 static mrb_value
 mrb_ary_shuffle_bang(mrb_state *mrb, mrb_value ary)
 {
+ /*
+ * MSC compiler generating invalid instructions with optimization
+ * enabled
+ */
   mrb_int i;
   mrb_value max;
   mrb_value r = mrb_nil_value();
-- 
cgit v1.2.3


From b8d896e56ab382b89c4980c0dc0efaca23f3a2c9 Mon Sep 17 00:00:00 2001
From: Rory OConnell <19547+RoryO@users.noreply.github.com>
Date: Fri, 26 Jun 2020 21:16:17 -0700
Subject: Narrower scope working around MSC bug

---
 mrbgems/mruby-random/src/random.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

(limited to 'mrbgems/mruby-random/src')

diff --git a/mrbgems/mruby-random/src/random.c b/mrbgems/mruby-random/src/random.c
index 6f31b15a6..f1834848d 100644
--- a/mrbgems/mruby-random/src/random.c
+++ b/mrbgems/mruby-random/src/random.c
@@ -210,18 +210,18 @@ random_m_srand(mrb_state *mrb, mrb_value self)
  *  Shuffles elements in self in place.
  */
 
-#if defined _MSC_VER && _MSC_VER >= 1900
-#pragma optimize( "", off )
-#endif
 static mrb_value
 mrb_ary_shuffle_bang(mrb_state *mrb, mrb_value ary)
 {
+  mrb_int i;
+  mrb_value max;
  /*
  * MSC compiler generating invalid instructions with optimization
  * enabled
  */
-  mrb_int i;
-  mrb_value max;
+#if defined _MSC_VER && _MSC_VER >= 1923
+  volatile
+#endif
   mrb_value r = mrb_nil_value();
   rand_state *random;
 
-- 
cgit v1.2.3


From b1017b26513c5773b30b88b0675ab070356fb2a8 Mon Sep 17 00:00:00 2001
From: Rory OConnell <19547+RoryO@users.noreply.github.com>
Date: Fri, 26 Jun 2020 21:44:31 -0700
Subject: Reduce scope of volatile keyword for MSC bug

---
 mrbgems/mruby-random/src/random.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

(limited to 'mrbgems/mruby-random/src')

diff --git a/mrbgems/mruby-random/src/random.c b/mrbgems/mruby-random/src/random.c
index f1834848d..55bea5713 100644
--- a/mrbgems/mruby-random/src/random.c
+++ b/mrbgems/mruby-random/src/random.c
@@ -215,15 +215,18 @@ mrb_ary_shuffle_bang(mrb_state *mrb, mrb_value ary)
 {
   mrb_int i;
   mrb_value max;
+  mrb_value r = mrb_nil_value();
+  rand_state *random;
+
  /*
- * MSC compiler generating invalid instructions with optimization
+ * MSC compiler bug generating invalid instructions with optimization
  * enabled
  */
 #if defined _MSC_VER && _MSC_VER >= 1923
-  volatile
+  volatile mrb_value rr;
+  rr = r;
+  r = rr;
 #endif
-  mrb_value r = mrb_nil_value();
-  rand_state *random;
 
   if (RARRAY_LEN(ary) > 1) {
     mrb_get_args(mrb, "|o", &r);
-- 
cgit v1.2.3


From 3cf48713a2d39e624e9b755bfcfae6fb51a861c9 Mon Sep 17 00:00:00 2001
From: Rory OConnell <19547+RoryO@users.noreply.github.com>
Date: Mon, 29 Jun 2020 14:25:59 -0700
Subject: Work around more MSC optimzer bugs

---
 mrbgems/mruby-random/src/random.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

(limited to 'mrbgems/mruby-random/src')

diff --git a/mrbgems/mruby-random/src/random.c b/mrbgems/mruby-random/src/random.c
index 55bea5713..10c81b946 100644
--- a/mrbgems/mruby-random/src/random.c
+++ b/mrbgems/mruby-random/src/random.c
@@ -220,12 +220,30 @@ mrb_ary_shuffle_bang(mrb_state *mrb, mrb_value ary)
 
  /*
  * MSC compiler bug generating invalid instructions with optimization
- * enabled
+ * enabled. MSC errantly uses a hardcoded value with optimizations on
+ * when using a fixed value from a union.
+ * Creating a temp volatile variable and reassigning back to the original
+ * value tricks the compiler to not perform this optimization;
  */
 #if defined _MSC_VER && _MSC_VER >= 1923
-  volatile mrb_value rr;
-  rr = r;
-  r = rr;
+  /* C++ will not cast away volatile easily, so we cannot do something like
+   * volatile mrb_value rr = r; r = (mrb_value)rr; with C++.
+   * That cast does work with C.
+   * We also have to trick the compiler to not optimize away the const_cast entirely
+   * by creating and manipulating an intermediate volatile pointer.
+   */
+  volatile mrb_value *v_r;
+  volatile mrb_int ii;
+  mrb_value *p_r;
+  v_r = &r;
+  ii = 2;
+  v_r = v_r + 2;
+#if defined __cplusplus
+  p_r = const_cast<mrb_value*>(v_r - ii);
+#else
+  p_r = (mrb_value*)v_r - ii;
+#endif
+  r = *p_r;
 #endif
 
   if (RARRAY_LEN(ary) > 1) {
-- 
cgit v1.2.3