From 3a93ebd6fee0a42c4dece98f0baca9b7008cbfc6 Mon Sep 17 00:00:00 2001
From: Fan Yang <52458914+fanyang-mono@users.noreply.github.com>
Date: Fri, 31 Jan 2020 16:40:47 -0500
Subject: [PATCH] Abort cmov optimization, when one of the out blocks is try
 block (#18626)

---
 mono/mini/branch-opts.c | 16 +++++++-----
 mono/mini/iltests.il    | 66 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+), 6 deletions(-)

diff --git a/mono/mini/branch-opts.c b/mono/mini/branch-opts.c
index 15c2a76d674..67eabd7c082 100644
--- a/mono/mini/branch-opts.c
+++ b/mono/mini/branch-opts.c
@@ -304,6 +304,16 @@ mono_if_conversion (MonoCompile *cfg)
 		MonoBasicBlock *bb1, *bb2;
 
 	restart:
+		if (!(bb->out_count == 2 && !bb->extended))
+			continue;
+
+		bb1 = bb->out_bb [0];
+		bb2 = bb->out_bb [1];
+
+		/* If either bb1 or bb2 is a try block, abort the optimization attempt. */
+		if (bb1->try_start || bb2->try_start)
+			continue;
+
 		/* Look for the IR code generated from cond ? a : b
 		 * which is:
 		 * BB:
@@ -315,12 +325,6 @@ mono_if_conversion (MonoCompile *cfg)
 		 * <var> <- <b>
 		 * br BB3
 		 */
-		if (!(bb->out_count == 2 && !bb->extended))
-			continue;
-
-		bb1 = bb->out_bb [0];
-		bb2 = bb->out_bb [1];
-
 		if (bb1->in_count == 1 && bb2->in_count == 1 && bb1->out_count == 1 && bb2->out_count == 1 && bb1->out_bb [0] == bb2->out_bb [0]) {
 			MonoInst *compare, *branch, *ins1, *ins2, *cmov, *move, *tmp;
 			MonoBasicBlock *true_bb, *false_bb;
diff --git a/mono/mini/iltests.il b/mono/mini/iltests.il
index 40c55e63e9b..ba6aba836d4 100644
--- a/mono/mini/iltests.il
+++ b/mono/mini/iltests.il
@@ -3491,4 +3491,70 @@ L3:
 	ret
    }
 */
+
+	.method public hidebysig static string cmov_try_block_helper (string s) cil managed noinlining
+  	{
+		// Code size       43 (0x2b)
+		.maxstack  2
+		.locals init (bool V_0, string V_1)
+		IL_0000:  nop
+		IL_0001:  ldarg.0
+		IL_0002:  callvirt   instance int32 [mscorlib]System.String::get_Length()
+		IL_0007:  ldc.i4.0
+		IL_0008:  ceq
+		IL_000a:  stloc.0
+		IL_000b:  ldloc.0
+		IL_000c:  brfalse.s  IL_0016
+
+		IL_000e:  ldstr	  "Empty"
+		IL_0013:  stloc.1
+		IL_0014:  br.s	  IL_0029
+
+		IL_0016:  nop
+		.try
+		{
+		  IL_0017:  nop
+		  IL_0018:  ldarg.0
+		  IL_0019:  stloc.1
+		  IL_001a:  leave.s   IL_0029
+		}  // end .try
+		catch [mscorlib]System.Exception
+		{
+		  IL_001c:  pop
+		  IL_001d:  nop
+		  IL_001e:  nop
+		  IL_001f:  leave.s   IL_0021
+		}  // end handler
+		IL_0021:  ldstr  "Should not happen"
+		IL_0026:  stloc.1
+		IL_0027:  br.s   IL_0029
+
+		IL_0029:  ldloc.1
+		IL_002a:  ret
+	}
+
+	.method public hidebysig static int32 test_1_cmov_try_block() cil managed
+	{
+		// Code size       37 (0x25)
+		.maxstack  2
+		.locals init (string V_0, bool V_1, int32 V_2)
+		IL_0000:  nop
+		IL_0001:  ldstr  "abc"
+		IL_0006:  call   string Tests::cmov_try_block_helper(string)
+		IL_000d:  ldstr  "abc"
+		IL_0012:  call   bool [mscorlib]System.String::op_Equality(string,string)
+		IL_0019:  brfalse.s  IL_001f
+
+		IL_001b:  ldc.i4.1
+		IL_001c:  stloc.2
+		IL_001d:  br.s   IL_0023
+
+		IL_001f:  ldc.i4.0
+		IL_0020:  stloc.2
+		IL_0021:  br.s   IL_0023
+
+		IL_0023:  ldloc.2
+		IL_0024:  ret
+	 }
+
 }
-- 
2.11.4.GIT