[hwasan] add musttail IR test.

[fmayer]

Summary

we currently only have a test at the clang level

[fmayer]

remove comment

[fmayer]

improve test

[morehouse]

LGTM

llvm/test/Instrumentation/HWAddressSanitizer/musttail.ll

+; Regression test for a compiler bug that caused a crash when instrumenting code
+; using musttail.
+
+; RUN: opt -S -passes=hwasan -hwasan-use-stack-safety=0 %s -o - | FileCheck %s
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-arm-unknown-eabi"
+
+define dso_local noundef i32 @_Z3bari(i32 noundef %0) sanitize_hwaddress {
+  %2 = alloca i32, align 4
+  store i32 %0, i32* %2, align 4
+  %3 = load i32, i32* %2, align 4
+  ret i32 %3
+}
+
+define dso_local noundef i32 @_Z3fooi(i32 noundef %0) sanitize_hwaddress {
+  %2 = alloca i32, align 4
+  %3 = alloca i32, align 4
+  store i32 %0, i32* %2, align 4
+  store volatile i32 5, i32* %3, align 4
+  %4 = load i32, i32* %2, align 4
+  %5 = load volatile i32, i32* %3, align 4
+  %6 = add nsw i32 %4, %5
+  ; Check we untag before the musttail.
+  ; CHECK: call void @llvm.memset.p0i8.i64
+  ; CHECK: musttail call
+  ; CHECK-NOT: call void @llvm.memset.p0i8.i64
+  %7 = musttail call noundef i32 @_Z3bari(i32 noundef %6)
+  ret i32 %7
+}