1 files changed, 139 insertions, 0 deletions
diff --git a/test/CodeGen/X86/conditional-tailcall-samedest.mir b/test/CodeGen/X86/conditional-tailcall-samedest.mir
new file mode 100644
index 0000000000000..c18a98be53f3b
--- /dev/null
+++ b/test/CodeGen/X86/conditional-tailcall-samedest.mir
@@ -0,0 +1,139 @@
+# RUN: llc -run-pass=branch-folder %s -o - | FileCheck %s
+
+# PR33980
+
+# Don't form conditional tail calls when the original conditional branch has
+# the same true and false destination. Otherwise, when we remove the tail call
+# successor we will also remove the fallthrough successor from the CFG.
+
+# CHECK: body:             |
+# CHECK:   bb.0.entry:
+# CHECK:     successors: %bb.1.sw.bb(0x40000000)
+# CHECK:     liveins: %edi
+# CHECK:     CMP32ri8 killed %edi, 2, implicit-def %eflags
+# CHECK:     TCRETURNdi64cc @mergeable_conditional_tailcall
+
+# This was the unconditional branch to a dead MBB that we left behind before
+# this bug was fixed.
+# CHECK-NOT: JMP_1 %bb.-1
+
+--- |
+  ; ModuleID = 't.ll'
+  source_filename = "t.ll"
+  target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+  target triple = "x86_64--linux"
+  
+  @static_local_guard = external global i64, align 8
+  
+  ; Function Attrs: optsize
+  define void @f(i32 %arg) #0 {
+  entry:
+    switch i32 %arg, label %sw.epilog [
+      i32 0, label %sw.bb
+      i32 1, label %sw.bb
+      i32 2, label %sw.bb2
+    ]
+  
+  sw.bb:                                            ; preds = %entry, %entry
+    %tmp = load atomic i8, i8* bitcast (i64* @static_local_guard to i8*) acquire, align 8
+    %guard.uninitialized.i = icmp eq i8 %tmp, 0
+    br i1 %guard.uninitialized.i, label %init.check.i, label %return, !prof !0
+  
+  init.check.i:                                     ; preds = %sw.bb
+    tail call void @initialize_static_local(i64* nonnull @static_local_guard)
+    ret void
+  
+  sw.bb2:                                           ; preds = %entry
+    tail call void @mergeable_conditional_tailcall()
+    ret void
+  
+  sw.epilog:                                        ; preds = %entry
+    tail call void @mergeable_conditional_tailcall()
+    ret void
+  
+  return:                                           ; preds = %sw.bb
+    ret void
+  }
+  
+  declare void @mergeable_conditional_tailcall()
+  
+  declare void @initialize_static_local(i64*)
+  
+  ; Function Attrs: nounwind
+  declare void @llvm.stackprotector(i8*, i8**) #1
+  
+  attributes #0 = { optsize }
+  attributes #1 = { nounwind }
+  
+  !0 = !{!"branch_weights", i32 1, i32 1048575}
+
+...
+---
+name:            f
+alignment:       0
+exposesReturnsTwice: false
+legalized:       false
+regBankSelected: false
+selected:        false
+tracksRegLiveness: true
+registers:       
+liveins:         
+  - { reg: '%edi', virtual-reg: '' }
+frameInfo:       
+  isFrameAddressTaken: false
+  isReturnAddressTaken: false
+  hasStackMap:     false
+  hasPatchPoint:   false
+  stackSize:       0
+  offsetAdjustment: 0
+  maxAlignment:    0
+  adjustsStack:    false
+  hasCalls:        false
+  stackProtector:  ''
+  maxCallFrameSize: 0
+  hasOpaqueSPAdjustment: false
+  hasVAStart:      false
+  hasMustTailInVarArgFunc: false
+  savePoint:       ''
+  restorePoint:    ''
+fixedStack:      
+stack:           
+constants:       
+body:             |
+  bb.0.entry:
+    successors: %bb.2.sw.bb(0x40000000), %bb.1.entry(0x40000000)
+    liveins: %edi
+  
+    CMP32ri8 killed %edi, 2, implicit-def %eflags
+    JB_1 %bb.2.sw.bb, implicit %eflags
+    JMP_1 %bb.1.entry
+  
+  bb.1.entry:
+    successors: %bb.4.sw.bb2(0x40000000), %bb.5.sw.epilog(0x40000000)
+    liveins: %eflags
+  
+    JE_1 %bb.4.sw.bb2, implicit killed %eflags
+    JMP_1 %bb.5.sw.epilog
+  
+  bb.2.sw.bb:
+    successors: %bb.3.init.check.i(0x00000800), %bb.6.return(0x7ffff800)
+  
+    %al = ACQUIRE_MOV8rm %rip, 1, _, @static_local_guard, _ :: (volatile load acquire 1 from `i8* bitcast (i64* @static_local_guard to i8*)`, align 8)
+    TEST8rr killed %al, %al, implicit-def %eflags
+    JNE_1 %bb.6.return, implicit killed %eflags
+    JMP_1 %bb.3.init.check.i
+  
+  bb.3.init.check.i:
+    dead %edi = MOV32ri64 @static_local_guard, implicit-def %rdi
+    TCRETURNdi64 @initialize_static_local, 0, csr_64, implicit %rsp, implicit %rdi
+  
+  bb.4.sw.bb2:
+    TCRETURNdi64 @mergeable_conditional_tailcall, 0, csr_64, implicit %rsp
+  
+  bb.5.sw.epilog:
+    TCRETURNdi64 @mergeable_conditional_tailcall, 0, csr_64, implicit %rsp
+  
+  bb.6.return:
+    RET 0
+
+...