[HotColdSplit] Do not split out `resume` instructions

Resumes that are not reachable from a cleanup landing pad are considered
to be unreachable. It’s not safe to split them out.

rdar://47808235

llvm-svn: 353242

3 files changed, 24 insertions, 8 deletions

diff --git a/llvm/lib/Transforms/IPO/HotColdSplitting.cpp b/llvm/lib/Transforms/IPO/HotColdSplitting.cpp
index 36dd6fa4be7..65e7938720d 100644
--- a/llvm/lib/Transforms/IPO/HotColdSplitting.cpp
+++ b/llvm/lib/Transforms/IPO/HotColdSplitting.cpp
@@ -135,8 +135,12 @@ static bool mayExtractBlock(const BasicBlock &BB) {
   // EH pads are unsafe to outline because doing so breaks EH type tables. It
   // follows that invoke instructions cannot be extracted, because CodeExtractor
   // requires unwind destinations to be within the extraction region.
-  return !BB.hasAddressTaken() && !BB.isEHPad() &&
-         !isa<InvokeInst>(BB.getTerminator());
+  //
+  // Resumes that are not reachable from a cleanup landing pad are considered to
+  // be unreachable. It’s not safe to split them out either.
+  auto Term = BB.getTerminator();
+  return !BB.hasAddressTaken() && !BB.isEHPad() && !isa<InvokeInst>(Term) &&
+         !isa<ResumeInst>(Term);
 }
 
 /// Mark \p F cold. Based on this assumption, also optimize it for minimum size.
diff --git a/llvm/test/Transforms/HotColdSplit/resume.ll b/llvm/test/Transforms/HotColdSplit/resume.ll
index 2b8ea7d91d9..67d2d241916 100644
--- a/llvm/test/Transforms/HotColdSplit/resume.ll
+++ b/llvm/test/Transforms/HotColdSplit/resume.ll
@@ -6,11 +6,17 @@ target triple = "x86_64-apple-macosx10.14.0"
 ; Consider `resume` to be cold.
 
 ; CHECK-LABEL: define {{.*}}@foo.cold.1(
-; CHECK: resume i32 undef
+; CHECK: call {{.*}}@sink(
 
-define i32 @foo(i32 %cond) personality i8 0 {
+declare void @sink() cold
+
+define i32 @foo() personality i8 0 {
 entry:
-  br i1 undef, label %resume-eh, label %normal
+  br i1 undef, label %pre-resume-eh, label %normal
+
+pre-resume-eh:
+  call void @sink()
+  br label %resume-eh
 
 resume-eh:
   resume i32 undef
diff --git a/llvm/test/Transforms/HotColdSplit/unwind.ll b/llvm/test/Transforms/HotColdSplit/unwind.ll
index adcae98d9bb..66e2f76e327 100644
--- a/llvm/test/Transforms/HotColdSplit/unwind.ll
+++ b/llvm/test/Transforms/HotColdSplit/unwind.ll
@@ -3,12 +3,15 @@
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.14.0"
 
-; Do not mark outlined functions which resume exception unwinding as noreturn.
+; Do not split out `resume` instructions.
 
 ; CHECK-LABEL: define {{.*}}@foo.cold.1(
-; CHECK: resume
+; CHECK: call {{.*}}@sink(
+; CHECK-NOT: resume i32 undef
+
 ; CHECK-NOT: noreturn
-define i32 @foo(i32 %cond) personality i8 0 {
+
+define i32 @foo() personality i8 0 {
 entry:
   invoke void @llvm.donothing() to label %normal unwind label %exception
 
@@ -19,6 +22,9 @@ exception:
 continue_exception:
   call void @sideeffect(i32 0)
   call void @sink()
+  br label %resume-eh
+
+resume-eh:
   resume i32 undef
 
 normal: