[HotColdSplit] Mark inherently cold functions as such

If an inherently cold function is found, mark it as cold. For now this
means applying the `cold` and `minsize` attributes.

As a drive-by, revisit and clean up the criteria for considering a
function for splitting. Add tests.

llvm-svn: 351623

3 files changed, 68 insertions, 2 deletions

diff --git a/llvm/test/Transforms/HotColdSplit/X86/do-not-split.ll b/llvm/test/Transforms/HotColdSplit/X86/do-not-split.ll
index 8622f03b2ed..448e63ab1de 100644
--- a/llvm/test/Transforms/HotColdSplit/X86/do-not-split.ll
+++ b/llvm/test/Transforms/HotColdSplit/X86/do-not-split.ll
@@ -43,6 +43,37 @@ entry:
   br i1 undef, label %if.then, label %if.end
 
 if.then:                                          ; preds = %entry
+  call void @sink()
+  br label %if.end
+
+if.end:                                           ; preds = %entry
+  ret void
+}
+
+; Do not split `noinline` functions.
+; CHECK-LABEL: @noinline_func
+; CHECK-NOT: noinline_func.cold.1
+define void @noinline_func() noinline {
+entry:
+  br i1 undef, label %if.then, label %if.end
+
+if.then:                                          ; preds = %entry
+  call void @sink()
+  br label %if.end
+
+if.end:                                           ; preds = %entry
+  ret void
+}
+
+; Do not split `alwaysinline` functions.
+; CHECK-LABEL: @alwaysinline_func
+; CHECK-NOT: alwaysinline_func.cold.1
+define void @alwaysinline_func() alwaysinline {
+entry:
+  br i1 undef, label %if.then, label %if.end
+
+if.then:                                          ; preds = %entry
+  call void @sink()
   br label %if.end
 
 if.end:                                           ; preds = %entry
diff --git a/llvm/test/Transforms/HotColdSplit/addr-taken.ll b/llvm/test/Transforms/HotColdSplit/addr-taken.ll
new file mode 100644
index 00000000000..f2f448c8a46
--- /dev/null
+++ b/llvm/test/Transforms/HotColdSplit/addr-taken.ll
@@ -0,0 +1,27 @@
+; 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"
+
+; CHECK: define {{.*}} @foo{{.*}}#[[outlined_func_attr:[0-9]+]]
+define void @foo() noreturn cold {
+  unreachable
+}
+
+; CHECK: define {{.*}} @bar.cold.1{{.*}}#[[outlined_func_attr]]
+define void @bar() {
+  br i1 undef, label %normal, label %exit
+
+normal:
+  unreachable
+
+exit:
+  ret void
+}
+
+@take_addr_of_foo = global void ()* @foo
+@take_addr_of_bar = global void ()* @bar
+
+; CHECK: attributes #[[outlined_func_attr]] = {
+; CHECK-SAME: cold
+; CHECK-SAME: minsize
diff --git a/llvm/test/Transforms/HotColdSplit/minsize.ll b/llvm/test/Transforms/HotColdSplit/minsize.ll
index 6955c5c79eb..36bd0340718 100644
--- a/llvm/test/Transforms/HotColdSplit/minsize.ll
+++ b/llvm/test/Transforms/HotColdSplit/minsize.ll
@@ -17,7 +17,15 @@ if.else:
   ret void
 }
 
+; CHECK: define {{.*}} @foo{{.*}}#[[outlined_func_attr:[0-9]+]]
+define void @foo() cold {
+  ret void
+}
+
 declare void @sink() cold
 
-; CHECK: define {{.*}} @fun.cold.1{{.*}}#[[outlined_func_attr:[0-9]+]]
-; CHECK: attributes #[[outlined_func_attr]] = { {{.*}}minsize
+; CHECK: define {{.*}} @fun.cold.1{{.*}}#[[outlined_func_attr]]
+
+; CHECK: attributes #[[outlined_func_attr]] = {
+; CHECK-SAME: cold
+; CHECK-SAME: minsize