From: Vedant Kumar <vsk@apple.com>
Date: Thu, 17 Jan 2019 22:35:47 +0000 (+0000)
Subject: [HotColdSplit] Consider resume instructions to be cold
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=390962bc3eb14cffd34318727ef82ca874f578a8;p=llvm

[HotColdSplit] Consider resume instructions to be cold

Resuming exception unwinding is roughly as unlikely as throwing an
exception.

Tested on LNT+externals (in particular, the C++ EH regression tests
provide end-to-end test coverage), as well as with a full build of iOS.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351491 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/IPO/HotColdSplitting.cpp b/lib/Transforms/IPO/HotColdSplitting.cpp
index 2cf8af35401..577f270863c 100644
--- a/lib/Transforms/IPO/HotColdSplitting.cpp
+++ b/lib/Transforms/IPO/HotColdSplitting.cpp
@@ -101,7 +101,7 @@ bool blockEndsInUnreachable(const BasicBlock &BB) {
 
 bool unlikelyExecuted(BasicBlock &BB) {
   // Exception handling blocks are unlikely executed.
-  if (BB.isEHPad())
+  if (BB.isEHPad() || isa<ResumeInst>(BB.getTerminator()))
     return true;
 
   // The block is cold if it calls/invokes a cold function.
diff --git a/test/Transforms/HotColdSplit/resume.ll b/test/Transforms/HotColdSplit/resume.ll
new file mode 100644
index 00000000000..cbda078da90
--- /dev/null
+++ b/test/Transforms/HotColdSplit/resume.ll
@@ -0,0 +1,20 @@
+; RUN: opt -hotcoldsplit -hotcoldsplit-threshold=0 -S < %s | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.14.0"
+
+; Consider `resume` to be cold.
+
+; CHECK-LABEL: define {{.*}}@foo.cold.1(
+; CHECK: resume i32 undef
+
+define i32 @foo(i32 %cond) personality i8 0 {
+entry:
+  br i1 undef, label %resume-eh, label %normal
+
+resume-eh:
+  resume i32 undef
+
+normal:
+  ret i32 0
+}