diff --git a/suite/tests/CMakeLists.txt b/suite/tests/CMakeLists.txt
index 1627c9f1287..45bd5bf0d6c 100644
--- a/suite/tests/CMakeLists.txt
+++ b/suite/tests/CMakeLists.txt
@@ -279,6 +279,9 @@ if (UNIX)
   string(REGEX REPLACE "-Wall" "" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
   # some tests rely on specific "nop;nop" patterns that optimization ruins
   # we should probably move the -O from top level into core/CMakeLists.txt
+  #
+  # -O3 is selectively re-added to some tests using the add_sve_flags() or
+  # optimize() functions
   string(REGEX REPLACE "-O[0-9]? " " " CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
 else (UNIX)
   # W2 is default (we're using W3).  We should also replace
@@ -474,6 +477,70 @@ function(append_link_flags target newflags)
     LINK_FLAGS "${cur_ldflags} ${newflags}")
 endfunction(append_link_flags)
 
+# It would be nice to get rid of the
+# string(REGEX REPLACE "-O[0-9]? " " " CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
+# line above and instead selectively remove -O3 from tests that cannot
+# support it.
+# This was investigated and proved to be non trivial as the client tests
+# use _DR_set_compile_flags() to set the compile flags whereas the core
+# tests use set_cflags(). _DR_set_compile_flags() is a public function and we
+# didn't want to add a blocklist in there.
+# For now we create a list of tests that can be built with -O3.
+# This is for AARCH64 UNIX only.
+# TODO i#6429 Change this allowlist to a blocklist.
+set(sve_tests
+      simple_app api.ir api.ir_negative api.ir_v81 api.ir_v82 api.ir_v83 api.ir_v84
+      api.ir_v86 api.ir_sve api.ir_sve2 api.ir-static api.drdecode common.broadfun
+      common.fib common.nzcv common.getretaddr common.segfault
+      common.allasm_aarch64_isa common.allasm_aarch64_cache allasm_aarch64_prefetch
+      allasm_aarch64_flush libutil.frontend_test libutil.drconfig_test
+      client.call-retarget client.modules client.annotation-concurrency
+      client.partial_module_map client.execfault client.events client.events_cpp
+      client.timer client.mangle_suspend client.syscall-mod client.signal
+      client.cleancallsig client.file_io client.cleancall-opt-1 client.inline
+      client.null_instrument client.large_options client.stolen-reg-index
+      client.gonative client.drmgr-test client.drx_buf-test
+      client.drbbdup-drwrap-test client.drbbdup-emul-test client.process-id
+      client.drreg-test client.low_on_memory client.tls client.drx-scattergather
+      client.drwrap-test client.drwrap-drreg-test drstatecmp-fuzz-app
+      client.drutil-test client.stolen-reg client.ldstex api.dis-a64 api.reenc-a64
+      api.opnd api.detach api.detach_state api.detach_signal api.detach_spawn
+      api.detach_spawn_stress_FLAKY api.detach_spawn_quick_exit api.ibl-stress
+      api.ibl-stress-aarch64-far-link_LONG api.static_startstop api.static_noclient
+      api.static_noinit api.static_detach api.static_prepop
+      api.static_reattach_client_flags api.static_crash api.static_sideline_FLAKY
+      api.static_symbols api.static_maps_mixup_yesvars
+      api.static_maps_mixup_novars_FLAKY api.thread_churn client.app_args
+      client.destructor builtin_prefetch tool.multiproc stride_benchmark
+      tool.fib_plus tool.heap_test tool.drcacheoff.gencode linux.eintr
+      linux.execve-sub linux.execve-null linux.execve-config linux.execv
+      linux.execve-rec linux.exit linux.fork linux.fork-sleep linux.infinite
+      linux.longjmp linux.prctl linux.mmap linux.zero-length-mem-ranges
+      linux.sigaction linux.syscall_pwait linux.sigaction_nosignals linux.thread
+      linux.threadexit linux.threadexit2 linux.signalfd linux.alarm
+      linux.signal_racesys linux.signal_pre_syscall linux.bad-signal-stack
+      linux.sigsuspend linux.sigmask linux.mangle_asynch linux.app_tls
+      linux.readlink linux.fib-conflict linux.fib-static linux.fib-pie linux.vfork
+      pthreads.pthreads pthreads.pthreads_exit pthreads.ptsig
+      pthreads.pthreads_fork_FLAKY security-linux.trampoline linux.infloop
+      linux.rseq_disable security-common.codemod security-common.ret_noncall_trace
+      security-common.retnonexisting security-common.TestAllocWE
+      security-common.TestMemProtChg_FLAKY client.drx-test
+     )
+
+function(add_sve_flags target)
+  if (proc_supports_sve)
+    if (target IN_LIST sve_tests)
+      target_compile_options(${target} PRIVATE
+        -march=armv8.4-a+crypto+rcpc+sha3+sm4+sve+rng+ssbs+nodotprod
+        # Reinstate the -03 flag which is removed with the
+        # string(REGEX REPLACE "-O[0-9]? " " " CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
+        # line above.
+        -O3)
+    endif()
+  endif()
+endfunction(add_sve_flags)
+
 function(add_exe test source)
   get_filename_component(srcbase ${source} NAME_WE)
   get_filename_component(srcpath ${source} PATH)
@@ -553,6 +620,10 @@ function(add_exe test source)
       "${CMAKE_GENERATOR}" MATCHES "Visual Studio")
     add_dependencies(${test} ${gen_asm_tgt})
   endif ()
+
+  # AARCH64 AND UNIX only
+  add_sve_flags(${test})
+
 endfunction(add_exe)
 
 # normal app
@@ -1699,7 +1770,11 @@ function(use_MD_not_MTd source_file)
   endif ()
 endfunction()
 
-# optimize the target
+# The -O3 flag is removed above with the
+# string(REGEX REPLACE "-O[0-9]? " " " CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
+# line. -O3 is then selectively re-added with this function or add_sve_flags().
+# It will be desirable to one day remove the "REGEX REPLACE" line and just
+# remove -O3 for targets that cannot support it.
 function(optimize target)
   if (UNIX)
     append_property_string(TARGET ${target} COMPILE_FLAGS "-O3")
diff --git a/suite/tests/client-interface/drx-test.c b/suite/tests/client-interface/drx-test.c
index 56a79e6e070..4c4d391f982 100644
--- a/suite/tests/client-interface/drx-test.c
+++ b/suite/tests/client-interface/drx-test.c
@@ -241,7 +241,9 @@ main(int argc, char **argv)
         /* child */
         int iter = 0;
         close(pipefd[0]); /* close unused read end */
-        write(pipefd[1], &buf, sizeof(buf));
+        if (write(pipefd[1], &buf, sizeof(buf)) == -1) {
+            perror("write to pipe failed\n");
+        }
         close(pipefd[1]);
         /* spin until parent kills us or we time out */
         while (iter++ < 12) {
diff --git a/suite/tests/linux/eintr.c b/suite/tests/linux/eintr.c
index d27e7798973..1f2196d8978 100644
--- a/suite/tests/linux/eintr.c
+++ b/suite/tests/linux/eintr.c
@@ -127,7 +127,8 @@ main(int argc, char **argv)
     child_ready = false;
     pthread_mutex_unlock(&lock);
 
-    write(pipefd[1], "ab", 2);
+    if (write(pipefd[1], "ab", 2) == -1)
+        perror("Failed to write to pipe\n");
 
     if (pthread_join(thread, &retval) != 0)
         perror("failed to join thread");
diff --git a/suite/tests/linux/tool.drcov.eintr.template b/suite/tests/linux/tool.drcov.eintr.template
index ccb79bd51a5..784935b207c 100644
--- a/suite/tests/linux/tool.drcov.eintr.template
+++ b/suite/tests/linux/tool.drcov.eintr.template
@@ -44,12 +44,13 @@ DA:126,1
 DA:127,1
 DA:128,1
 DA:130,1
-DA:132,1
-DA:133,0
-DA:135,1
+DA:131,0
+DA:133,1
+DA:134,0
 DA:136,1
-DA:138,1
+DA:137,1
 DA:139,1
-DA:141,1
+DA:140,1
 DA:142,1
+DA:143,1
 end_of_record