[SimplifyCFG] Tail-merge calls with sideeffects

This was deliberately disabled during my rewrite of SinkIfThenToEnd to keep behaviour
at least vaguely consistent with the previous version and keep it as close to NFC as
I could.

There's no real reason not to merge sideeffect calls though, so let's do it! Small fixup
along the way to ensure we don't create indirect calls.

Should fix PR28964.

llvm-svn: 280215

1 files changed, 24 insertions, 1 deletions

diff --git a/llvm/test/Transforms/SimplifyCFG/sink-common-code.ll b/llvm/test/Transforms/SimplifyCFG/sink-common-code.ll
index e3a86dc9385..fe501b980aa 100644
--- a/llvm/test/Transforms/SimplifyCFG/sink-common-code.ll
+++ b/llvm/test/Transforms/SimplifyCFG/sink-common-code.ll
@@ -344,6 +344,29 @@ if.end:
 ; CHECK-NOT: load
 ; CHECK-NOT: store
 
+; The call should be commoned.
+define i32 @test13a(i1 zeroext %flag, i32 %w, i32 %x, i32 %y) {
+entry:
+  br i1 %flag, label %if.then, label %if.else
+
+if.then:
+  %sv1 = call i32 @bar(i32 %x)
+  br label %if.end
+
+if.else:
+  %sv2 = call i32 @bar(i32 %y)
+  br label %if.end
+
+if.end:
+  %p = phi i32 [ %sv1, %if.then ], [ %sv2, %if.else ]
+  ret i32 1
+}
+declare i32 @bar(i32)
+
+; CHECK-LABEL: test13a
+; CHECK: %[[x:.*]] = select i1 %flag
+; CHECK: call i32 @bar(i32 %[[x]])
+
 ; CHECK: !0 = !{!1, !1, i64 0}
 ; CHECK: !1 = !{!"float", !2}
-; CHECK: !2 = !{!"an example type tree"}
\ No newline at end of file
+; CHECK: !2 = !{!"an example type tree"}