Add missing test file from r329855

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_60@329857 91177308-0d34-0410-b5e6-96231b3b80d8

Author: tstellar

test/Transforms/IPConstantProp/musttail-call.ll

@@ -0,0 +1,58 @@
+; RUN: opt < %s -ipsccp -S | FileCheck %s
+; PR36485
+; musttail call result can\'t be replaced with a constant, unless the call
+; can be removed
+
+declare i32 @external()
+
+define i8* @start(i8 %v) {
+  %c1 = icmp eq i8 %v, 0
+  br i1 %c1, label %true, label %false
+true:
+  ; CHECK: %ca = musttail call i8* @side_effects(i8 %v)
+  ; CHECK: ret i8* %ca
+  %ca = musttail call i8* @side_effects(i8 %v)
+  ret i8* %ca
+false:
+  %c2 = icmp eq i8 %v, 1
+  br i1 %c2, label %c2_true, label %c2_false
+c2_true:
+  ; CHECK: %ca1 = musttail call i8* @no_side_effects(i8 %v)
+  ; CHECK: ret i8* %ca1
+  %ca1 = musttail call i8* @no_side_effects(i8 %v)
+  ret i8* %ca1
+c2_false:
+  ; CHECK: %ca2 = musttail call i8* @dont_zap_me(i8 %v)
+  ; CHECK: ret i8* %ca2
+  %ca2 = musttail call i8* @dont_zap_me(i8 %v)
+  ret i8* %ca2
+}
+
+define internal i8* @side_effects(i8 %v) {
+  %i1 = call i32 @external()
+
+  ; since this goes back to `start` the SCPP should be see that the return value
+  ; is always `null`.
+  ; The call can't be removed due to `external` call above, though.
+
+  ; CHECK: %ca = musttail call i8* @start(i8 %v)
+  %ca = musttail call i8* @start(i8 %v)
+
+  ; Thus the result must be returned anyway
+  ; CHECK: ret i8* %ca
+  ret i8* %ca
+}
+
+define internal i8* @no_side_effects(i8 %v) readonly nounwind {
+  ; CHECK: ret i8* null
+  ret i8* null
+}
+
+define internal i8* @dont_zap_me(i8 %v) {
+  %i1 = call i32 @external()
+
+  ; The call to this function cannot be removed due to side effects. Thus the
+  ; return value should stay as it is, and should not be zapped.
+  ; CHECK: ret i8* null
+  ret i8* null
+}