[FuncSpec] Add test for a call site that will never be executed. NFC.

Author: Sjoerd Meijer

llvm/test/Transforms/FunctionSpecialization/function-specialization-noexec.ll

@@ -0,0 +1,36 @@
+; RUN: opt -function-specialization -force-function-specialization -S < %s | FileCheck %s
+
+; The if.then block is not executed, so check that we don't specialise here.
+
+; CHECK-NOT: @func.1(
+; CHECK-NOT: @func.2(
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+
+@A = external dso_local constant i32, align 4
+@B = external dso_local constant i32, align 4
+
+define dso_local i32 @bar(i32 %x, i32 %y) {
+entry:
+  %tobool = icmp ne i32 %x, 0
+  br i1 false, label %if.then, label %if.else
+
+if.then:
+  %call = call i32 @foo(i32 %x, i32* @A)
+  br label %return
+
+if.else:
+  %call1 = call i32 @foo(i32 %y, i32* @B)
+  br label %return
+
+return:
+  %retval.0 = phi i32 [ %call, %if.then ], [ %call1, %if.else ]
+  ret i32 %retval.0
+}
+
+define internal i32 @foo(i32 %x, i32* %b) {
+entry:
+  %0 = load i32, i32* %b, align 4
+  %add = add nsw i32 %x, %0
+  ret i32 %add
+}