Meta: Globally disable -Wpsabi

This warning is triggered when one accepts or returns vectors from a
function (that is not marked with [[gnu::target(...)]]) which would have
been otherwise passed in register if the current translation unit had
been compiled with more permissive flags wrt instruction selection (i.
e. if one adds -mavx2 to cmdline). This will never be a problem for us
since we (a) never use different instruction selection options across
ABI boundaries; (b) most of the affected functions are actually
TU-local.

Moreover, even if we somehow properly annotated all of the SIMD helpers,
calling them across ABI (or target) boundaries would still be very
dangerous because of inconsistent and bogus handling of
[[gnu::target(...)]] across compilers. See
llvm/llvm-project#64706 and
https://www.reddit.com/r/cpp/comments/17qowl2/comment/k8j2odi .

AK/SIMDExtras.h

@@ -10,13 +10,6 @@
 #include <AK/Concepts.h>
 #include <AK/SIMD.h>
 
-// Functions returning vectors or accepting vector arguments have different calling conventions
-// depending on whether the target architecture supports SSE or not. GCC generates warning "psabi"
-// when compiling for non-SSE architectures. We disable this warning because these functions
-// are static and should never be visible from outside the translation unit that includes this header.
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wpsabi"
-
 namespace AK::SIMD {
 
 // SIMD Vector Expansion
@@ -327,5 +320,3 @@ ALWAYS_INLINE static T elementwise_byte_reverse(T a)
 }
 
 }
-
-#pragma GCC diagnostic pop

AK/SIMDMath.h

@@ -11,13 +11,6 @@
 #include <AK/SIMDExtras.h>
 #include <math.h>
 
-// Functions returning vectors or accepting vector arguments have different calling conventions
-// depending on whether the target architecture supports SSE or not. GCC generates warning "psabi"
-// when compiling for non-SSE architectures. We disable this warning because these functions
-// are static and should never be visible from outside the translation unit that includes this header.
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wpsabi"
-
 namespace AK::SIMD {
 
 // Functions ending in "_int_range" only accept arguments within range [INT_MIN, INT_MAX].
@@ -90,5 +83,3 @@ ALWAYS_INLINE static f32x4 sqrt(f32x4 v)
 }
 
 }
-
-#pragma GCC diagnostic pop

Meta/CMake/common_compile_options.cmake

@@ -13,6 +13,19 @@ add_compile_options(-Wno-invalid-offsetof)
 add_compile_options(-Wno-unknown-warning-option)
 add_compile_options(-Wno-unused-command-line-argument)
 
+# This warning is triggered when one accepts or returns vectors from a function (that is not marked
+# with [[gnu::target(...)]]) which would have been otherwise passed in register if the current
+# translation unit had been compiled with more permissive flags wrt instruction selection (i. e. if
+# one adds -mavx2 to cmdline). This will never be a problem for us since we (a) never use
+# different instruction selection options across ABI boundaries; (b) most of the affected functions
+# are actually TU-local.
+#
+# Moreover, even if we somehow properly annotated all of the SIMD helpers, calling them across ABI
+# (or target) boundaries would still be very dangerous because of inconsistent and bogus handling of
+# [[gnu::target(...)]] across compilers. See https://github.com/llvm/llvm-project/issues/64706 and
+# https://www.reddit.com/r/cpp/comments/17qowl2/comment/k8j2odi .
+add_compile_options(-Wno-psabi)
+
 add_compile_options(-fno-exceptions)
 
 add_compile_options(-ffp-contract=off)

Userland/Libraries/LibCrypto/Hash/SHA1.cpp

@@ -15,7 +15,6 @@
 #    include <AK/SIMD.h>
 #    include <AK/SIMDExtras.h>
 #    include <cpuid.h>
-#    pragma GCC diagnostic ignored "-Wpsabi"
 #endif
 
 namespace Crypto::Hash {

Userland/Libraries/LibCrypto/Hash/SHA2.cpp

@@ -13,7 +13,6 @@
 #    include <AK/SIMD.h>
 #    include <AK/SIMDExtras.h>
 #    include <cpuid.h>
-#    pragma GCC diagnostic ignored "-Wpsabi"
 #endif
 
 namespace Crypto::Hash {

Userland/Libraries/LibGfx/ImageFormats/PNGWriter.cpp

@@ -15,8 +15,6 @@
 #include <LibGfx/Bitmap.h>
 #include <LibGfx/ImageFormats/PNGWriter.h>
 
-#pragma GCC diagnostic ignored "-Wpsabi"
-
 namespace Gfx {
 
 class PNGChunk {