[SimplifyCFG] Fix prof branch_weights MD while removing unreachable switch cases

SimplifyCFG has a bug that results in inconsistent prof branch_weights metadata
if unreachable switch cases are removed. This patch fixes this bug by making use
of the newly introduced SwitchInstProfUpdateWrapper class (see patch D62122).
A new test is created.

Differential Revision: https://reviews.llvm.org/D62186

llvm-svn: 363527

1 files changed, 35 insertions, 0 deletions

diff --git a/llvm/test/Transforms/SimplifyCFG/switch-profmd.ll b/llvm/test/Transforms/SimplifyCFG/switch-profmd.ll
new file mode 100644
index 00000000000..c17214e18f2
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/switch-profmd.ll
@@ -0,0 +1,35 @@
+; RUN: opt -S -simplifycfg < %s | FileCheck %s
+
+declare i32 @f(i32 %val)
+
+; Check that eliminating cases with unreachable branches keeps
+; prof branch_weights metadata consistent with switch instruction.
+define i32 @test_switch_to_unreachable(i32 %val) {
+; CHECK-LABEL: test_switch_to_unreachable
+; CHECK: switch
+; CHECK-NOT: i32 0, label %on0
+  switch i32 %val, label %otherwise [
+    i32 0, label %on0
+    i32 1, label %on1
+    i32 2, label %on2
+  ], !prof !{!"branch_weights", i32 99, i32 0, i32 1, i32 2}
+; CHECK: !prof ![[MD0:[0-9]+]]
+
+otherwise:
+  %result = call i32 @f(i32 -1)
+  ret i32 %result
+
+on0:
+  unreachable
+  ret i32 125
+
+on1:
+  %result1 = call i32 @f(i32 -2)
+  ret i32 %result1
+
+on2:
+  %result2 = call i32 @f(i32 -3)
+  ret i32 %result2
+}
+
+; CHECK: ![[MD0]] = !{!"branch_weights", i32 99, i32 2, i32 1}