Teach CodeGenPrep to look past bitcast when it's duplicating return instruction

into predecessor blocks to enable tail call optimization.

rdar://11958338


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160894 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 87 insertions, 0 deletions

diff --git a/test/CodeGen/X86/tailcall-cgp-dup.ll b/test/CodeGen/X86/tailcall-cgp-dup.ll
new file mode 100644
index 0000000000..a80b90f9ee
--- /dev/null
+++ b/test/CodeGen/X86/tailcall-cgp-dup.ll
@@ -0,0 +1,87 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin | FileCheck %s
+
+; Teach CGP to dup returns to enable tail call optimization.
+; rdar://9147433
+
+define i32 @foo(i32 %x) nounwind ssp {
+; CHECK: foo:
+entry:
+  switch i32 %x, label %return [
+    i32 1, label %sw.bb
+    i32 2, label %sw.bb1
+    i32 3, label %sw.bb3
+    i32 4, label %sw.bb5
+    i32 5, label %sw.bb7
+    i32 6, label %sw.bb9
+  ]
+
+sw.bb:                                            ; preds = %entry
+; CHECK: jmp _f1
+  %call = tail call i32 @f1() nounwind
+  br label %return
+
+sw.bb1:                                           ; preds = %entry
+; CHECK: jmp _f2
+  %call2 = tail call i32 @f2() nounwind
+  br label %return
+
+sw.bb3:                                           ; preds = %entry
+; CHECK: jmp _f3
+  %call4 = tail call i32 @f3() nounwind
+  br label %return
+
+sw.bb5:                                           ; preds = %entry
+; CHECK: jmp _f4
+  %call6 = tail call i32 @f4() nounwind
+  br label %return
+
+sw.bb7:                                           ; preds = %entry
+; CHECK: jmp _f5
+  %call8 = tail call i32 @f5() nounwind
+  br label %return
+
+sw.bb9:                                           ; preds = %entry
+; CHECK: jmp _f6
+  %call10 = tail call i32 @f6() nounwind
+  br label %return
+
+return:                                           ; preds = %entry, %sw.bb9, %sw.bb7, %sw.bb5, %sw.bb3, %sw.bb1, %sw.bb
+  %retval.0 = phi i32 [ %call10, %sw.bb9 ], [ %call8, %sw.bb7 ], [ %call6, %sw.bb5 ], [ %call4, %sw.bb3 ], [ %call2, %sw.bb1 ], [ %call, %sw.bb ], [ 0, %entry ]
+  ret i32 %retval.0
+}
+
+declare i32 @f1()
+
+declare i32 @f2()
+
+declare i32 @f3()
+
+declare i32 @f4()
+
+declare i32 @f5()
+
+declare i32 @f6()
+
+; rdar://11958338
+%0 = type opaque
+
+declare i8* @bar(i8*) uwtable optsize noinline ssp
+
+define hidden %0* @thingWithValue(i8* %self) uwtable ssp {
+entry:
+; CHECK: thingWithValue:
+; CHECK: jmp _bar
+  br i1 undef, label %if.then.i, label %if.else.i
+
+if.then.i:                                        ; preds = %entry
+  br label %someThingWithValue.exit
+
+if.else.i:                                        ; preds = %entry
+  %call4.i = tail call i8* @bar(i8* undef) optsize
+  br label %someThingWithValue.exit
+
+someThingWithValue.exit:                          ; preds = %if.else.i, %if.then.i
+  %retval.0.in.i = phi i8* [ undef, %if.then.i ], [ %call4.i, %if.else.i ]
+  %retval.0.i = bitcast i8* %retval.0.in.i to %0*
+  ret %0* %retval.0.i
+}