[inliner] Significantly improve the compile time in cases like PR19499
by avoiding inlining massive switches merely because they have no
instructions in them. These switches still show up where we fail to form
lookup tables, and in those cases they are actually going to cause
a very significant code size hit anyways, so inlining them is not the
right call. The right way to fix any performance regressions stemming
from this is to enhance the switch-to-lookup-table logic to fire in more
places.
This makes PR19499 about 5x less bad. It uncovers a second compile time
problem in that test case that is unrelated (surprisingly!).
llvm-svn: 207403
diff --git a/llvm/test/Transforms/Inline/switch.ll b/llvm/test/Transforms/Inline/switch.ll
new file mode 100644
index 0000000..c5dab53
--- /dev/null
+++ b/llvm/test/Transforms/Inline/switch.ll
@@ -0,0 +1,60 @@
+; RUN: opt < %s -inline -inline-threshold=20 -S | FileCheck %s
+
+define i32 @callee(i32 %a) {
+ switch i32 %a, label %sw.default [
+ i32 0, label %sw.bb0
+ i32 1, label %sw.bb1
+ i32 2, label %sw.bb2
+ i32 3, label %sw.bb3
+ i32 4, label %sw.bb4
+ i32 5, label %sw.bb5
+ i32 6, label %sw.bb6
+ i32 7, label %sw.bb7
+ i32 8, label %sw.bb8
+ i32 9, label %sw.bb9
+ ]
+
+sw.default:
+ br label %return
+
+sw.bb0:
+ br label %return
+
+sw.bb1:
+ br label %return
+
+sw.bb2:
+ br label %return
+
+sw.bb3:
+ br label %return
+
+sw.bb4:
+ br label %return
+
+sw.bb5:
+ br label %return
+
+sw.bb6:
+ br label %return
+
+sw.bb7:
+ br label %return
+
+sw.bb8:
+ br label %return
+
+sw.bb9:
+ br label %return
+
+return:
+ ret i32 42
+}
+
+define i32 @caller(i32 %a) {
+; CHECK-LABEL: @caller(
+; CHECK: call i32 @callee(
+
+ %result = call i32 @callee(i32 %a)
+ ret i32 %result
+}