diff --git a/Makefile b/Makefile
index 080c748..667ddfb 100644
--- a/Makefile
+++ b/Makefile
@@ -56,27 +56,6 @@ PASST_HEADERS = arch.h arp.h checksum.h conf.h dhcp.h dhcpv6.h icmp.h \
 	tcp_splice.h udp.h util.h
 HEADERS = $(PASST_HEADERS) seccomp.h
 
-# On gcc 11 and 12, with -O2 and -flto, tcp_hash() and siphash_20b(), if
-# inlined, seem to be hitting something similar to:
-#	https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78993
-# from the pointer arithmetic used from the tcp_tap_handler() path to get the
-# remote connection address.
-#
-# TODO: With the same combination, in ndp(), gcc optimises away the store of
-# hop_limit in the IPv6 header (temporarily set to the protocol number for
-# convenience, to mimic the ICMPv6 checksum pseudo-header) before the call to
-# csum_unaligned(). Mark csum_unaligned() as "noipa" as a quick work-around,
-# while we figure out if a corresponding gcc issue has already been reported.
-ifeq (,$(filter-out 11 12, $(shell $(CC) -dumpversion)))
-ifneq (,$(filter -flto%,$(FLAGS) $(CFLAGS) $(CPPFLAGS)))
-ifneq (,$(filter -O2,$(FLAGS) $(CFLAGS) $(CPPFLAGS)))
-	FLAGS += -DTCP_HASH_NOINLINE
-	FLAGS += -DSIPHASH_20B_NOINLINE
-	FLAGS += -DCSUM_UNALIGNED_NO_IPA
-endif
-endif
-endif
-
 C := \#include <linux/tcp.h>\nstruct tcp_info x = { .tcpi_snd_wnd = 0 };
 ifeq ($(shell printf "$(C)" | $(CC) -S -xc - -o - >/dev/null 2>&1; echo $$?),0)
 	FLAGS += -DHAS_SND_WND
diff --git a/checksum.c b/checksum.c
index 29769d9..9631f91 100644
--- a/checksum.c
+++ b/checksum.c
@@ -69,6 +69,8 @@
  *
  * Return: 32-bit sum of 16-bit words
 */
+/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
+__attribute__((optimize("-fno-strict-aliasing")))	/* See siphash_8b() */
 uint32_t sum_16b(const void *buf, size_t len)
 {
 	const uint16_t *p = buf;
@@ -107,9 +109,8 @@ uint16_t csum_fold(uint32_t sum)
  *
  * Return: 16-bit IPv4-style checksum
  */
-#if CSUM_UNALIGNED_NO_IPA
-__attribute__((__noipa__))	/* See comment in Makefile */
-#endif
+/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
+__attribute__((optimize("-fno-strict-aliasing")))	/* See siphash_8b() */
 uint16_t csum_unaligned(const void *buf, size_t len, uint32_t init)
 {
 	return (uint16_t)~csum_fold(sum_16b(buf, len) + init);
@@ -245,6 +246,8 @@ void csum_icmp6(struct icmp6hdr *icmp6hr,
  * - sum_a/sum_b unpacking is interleaved and not sequential to reduce stalls
  * - coding style adaptation
  */
+/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
+__attribute__((optimize("-fno-strict-aliasing")))	/* See siphash_8b() */
 static uint32_t csum_avx2(const void *buf, size_t len, uint32_t init)
 {
 	__m256i a, b, sum256, sum_a_hi, sum_a_lo, sum_b_hi, sum_b_lo, c, d;
@@ -391,6 +394,8 @@ less_than_128_bytes:
  *
  * Return: 16-bit folded, complemented checksum sum
  */
+/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
+__attribute__((optimize("-fno-strict-aliasing")))	/* See siphash_8b() */
 uint16_t csum(const void *buf, size_t len, uint32_t init)
 {
 	return (uint16_t)~csum_fold(csum_avx2(buf, len, init));
@@ -406,6 +411,8 @@ uint16_t csum(const void *buf, size_t len, uint32_t init)
  *
  * Return: 16-bit folded, complemented checksum
  */
+/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
+__attribute__((optimize("-fno-strict-aliasing")))	/* See siphash_8b() */
 uint16_t csum(const void *buf, size_t len, uint32_t init)
 {
 	return csum_unaligned(buf, len, init);
diff --git a/siphash.c b/siphash.c
index 811918b..e8b144d 100644
--- a/siphash.c
+++ b/siphash.c
@@ -104,6 +104,17 @@
  *
  * Return: the 64-bit hash output
  */
+/* Type-Based Alias Analysis (TBAA) optimisation in gcc 11 and 12 (-flto -O2)
+ * makes these functions essentially useless by allowing reordering of stores of
+ * input data across function calls. Not even declaring @in as char pointer is
+ * enough: disable gcc's interpretation of strict aliasing altogether. See also:
+ *
+ *	https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106706
+ *	https://stackoverflow.com/questions/2958633/gcc-strict-aliasing-and-horror-stories
+ *	https://lore.kernel.org/all/alpine.LFD.2.00.0901121128080.6528__33422.5328093909$1232291247$gmane$org@localhost.localdomain/
+ */
+/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
+__attribute__((optimize("-fno-strict-aliasing")))
 /* cppcheck-suppress unusedFunction */
 uint64_t siphash_8b(const uint8_t *in, const uint64_t *k)
 {
@@ -123,6 +134,8 @@ uint64_t siphash_8b(const uint8_t *in, const uint64_t *k)
  *
  * Return: 32 bits obtained by XORing the two halves of the 64-bit hash output
  */
+/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
+__attribute__((optimize("-fno-strict-aliasing")))	/* See siphash_8b() */
 /* cppcheck-suppress unusedFunction */
 uint32_t siphash_12b(const uint8_t *in, const uint64_t *k)
 {
@@ -148,9 +161,8 @@ uint32_t siphash_12b(const uint8_t *in, const uint64_t *k)
  *
  * Return: the 64-bit hash output
  */
-#if SIPHASH_20B_NOINLINE
-__attribute__((__noinline__))	/* See comment in Makefile */
-#endif
+/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
+__attribute__((optimize("-fno-strict-aliasing")))	/* See siphash_8b() */
 uint64_t siphash_20b(const uint8_t *in, const uint64_t *k)
 {
 	uint32_t *in32 = (uint32_t *)in;
@@ -179,6 +191,8 @@ uint64_t siphash_20b(const uint8_t *in, const uint64_t *k)
  *
  * Return: the 64-bit hash output
  */
+/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
+__attribute__((optimize("-fno-strict-aliasing")))	/* See siphash_8b() */
 /* cppcheck-suppress unusedFunction */
 uint32_t siphash_32b(const uint8_t *in, const uint64_t *k)
 {
@@ -205,6 +219,8 @@ uint32_t siphash_32b(const uint8_t *in, const uint64_t *k)
  *
  * Return: 32 bits obtained by XORing the two halves of the 64-bit hash output
  */
+/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
+__attribute__((optimize("-fno-strict-aliasing")))	/* See siphash_8b() */
 uint32_t siphash_36b(const uint8_t *in, const uint64_t *k)
 {
 	uint32_t *in32 = (uint32_t *)in;
diff --git a/tcp.c b/tcp.c
index 21c319d..cbd537e 100644
--- a/tcp.c
+++ b/tcp.c
@@ -1182,12 +1182,6 @@ static int tcp_hash_match(const struct tcp_tap_conn *conn,
  *
  * Return: hash value, already modulo size of the hash table
  */
-#if TCP_HASH_NOINLINE
-__attribute__((__noinline__))	/* See comment in Makefile */
-#endif
-__attribute__((optimize("O0")))	/* TODO: with -O2 and -flto on gcc 12.2,
-				 * siphash_20b() doesn't see 'addr', why?
-				 */
 static unsigned int tcp_hash(const struct ctx *c, const union inany_addr *addr,
 			     in_port_t tap_port, in_port_t sock_port)
 {