diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -763,6 +763,7 @@
   * Support intrinsic of ``_mm(256)_cvtneps_avx_pbh``.
 - ``-march=raptorlake`` and ``-march=meteorlake`` are now supported.
 - ``-march=sierraforest``, ``-march=graniterapids`` and ``-march=grandridge`` are now supported.
+- Lift _BitInt() supported max width from 128 to 8388608.
 
 WebAssembly Support in Clang
 ----------------------------
diff --git a/clang/lib/Basic/Targets/X86.h b/clang/lib/Basic/Targets/X86.h
--- a/clang/lib/Basic/Targets/X86.h
+++ b/clang/lib/Basic/Targets/X86.h
@@ -492,6 +492,9 @@
   ArrayRef<Builtin::Info> getTargetBuiltins() const override;
 
   bool hasBitIntType() const override { return true; }
+  size_t getMaxBitIntWidth() const override {
+    return llvm::IntegerType::MAX_INT_BITS;
+  }
 };
 
 class LLVM_LIBRARY_VISIBILITY NetBSDI386TargetInfo
@@ -799,6 +802,9 @@
   ArrayRef<Builtin::Info> getTargetBuiltins() const override;
 
   bool hasBitIntType() const override { return true; }
+  size_t getMaxBitIntWidth() const override {
+    return llvm::IntegerType::MAX_INT_BITS;
+  }
 };
 
 // x86-64 Windows target
diff --git a/clang/test/CodeGen/ext-int-cc.c b/clang/test/CodeGen/ext-int-cc.c
--- a/clang/test/CodeGen/ext-int-cc.c
+++ b/clang/test/CodeGen/ext-int-cc.c
@@ -131,10 +131,10 @@
 // are negated. This will give an error when a target does support larger
 // _BitInt widths to alert us to enable the test.
 void ParamPassing4(_BitInt(129) a) {}
-// LIN64-NOT: define{{.*}} void @ParamPassing4(ptr byval(i129) align 8 %{{.+}})
-// WIN64-NOT: define dso_local void @ParamPassing4(ptr %{{.+}})
-// LIN32-NOT: define{{.*}} void @ParamPassing4(ptr %{{.+}})
-// WIN32-NOT: define dso_local void @ParamPassing4(ptr %{{.+}})
+// LIN64: define{{.*}} void @ParamPassing4(ptr byval(i129) align 8 %{{.+}})
+// WIN64: define dso_local void @ParamPassing4(ptr %{{.+}})
+// LIN32: define{{.*}} void @ParamPassing4(ptr %{{.+}})
+// WIN32: define dso_local void @ParamPassing4(ptr %{{.+}})
 // NACL-NOT: define{{.*}} void @ParamPassing4(ptr byval(i129) align 8 %{{.+}})
 // NVPTX64-NOT: define{{.*}} void @ParamPassing4(ptr byval(i129) align 8 %{{.+}})
 // NVPTX-NOT: define{{.*}} void @ParamPassing4(ptr byval(i129) align 8 %{{.+}})
@@ -290,10 +290,10 @@
 
 #if __BITINT_MAXWIDTH__ > 128
 _BitInt(129) ReturnPassing5(void){}
-// LIN64-NOT: define{{.*}} void @ReturnPassing5(ptr noalias sret
-// WIN64-NOT: define dso_local void @ReturnPassing5(ptr noalias sret
-// LIN32-NOT: define{{.*}} void @ReturnPassing5(ptr noalias sret
-// WIN32-NOT: define dso_local void @ReturnPassing5(ptr noalias sret
+// LIN64: define{{.*}} void @ReturnPassing5(ptr noalias sret
+// WIN64: define dso_local void @ReturnPassing5(ptr noalias sret
+// LIN32: define{{.*}} void @ReturnPassing5(ptr noalias sret
+// WIN32: define dso_local void @ReturnPassing5(ptr noalias sret
 // NACL-NOT: define{{.*}} void @ReturnPassing5(ptr noalias sret
 // NVPTX64-NOT: define{{.*}} i129 @ReturnPassing5(
 // NVPTX-NOT: define{{.*}} i129 @ReturnPassing5(
diff --git a/clang/test/Lexer/bitint-constants.c b/clang/test/Lexer/bitint-constants.c
--- a/clang/test/Lexer/bitint-constants.c
+++ b/clang/test/Lexer/bitint-constants.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -std=c2x -fsyntax-only -verify -Wno-unused %s
+// RUN: %clang_cc1 -triple aarch64-unknown-unknown -std=c2x -fsyntax-only -verify -Wno-unused %s
 
 // Test that the preprocessor behavior makes sense.
 #if 1wb != 1
diff --git a/clang/test/Preprocessor/cuda-types.cu b/clang/test/Preprocessor/cuda-types.cu
--- a/clang/test/Preprocessor/cuda-types.cu
+++ b/clang/test/Preprocessor/cuda-types.cu
@@ -1,6 +1,6 @@
 // Check that types, widths, __CLANG_ATOMIC* macros, etc. match on the host and
-// device sides of CUDA compilations.  Note that we filter out long double, as
-// this is intentionally different on host and device.
+// device sides of CUDA compilations. Note that we filter out long double and
+// maxwidth of _BitInt(), as this is intentionally different on host and device.
 //
 // Also ignore __CLANG_ATOMIC_LLONG_LOCK_FREE on i386. The default host CPU for
 // an i386 triple is typically at least an i586, which has cmpxchg8b (Clang
@@ -14,40 +14,40 @@
 
 // RUN: %clang --cuda-host-only -nocudainc -target i386-unknown-linux-gnu -x cuda -E -dM -o - /dev/null \
 // RUN:   | grep -E 'define __[^ ]*(TYPE|MAX|SIZEOF|WIDTH)|define __CLANG_ATOMIC' \
-// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|_ATOMIC_LLONG_LOCK_FREE' > %t/i386-host-defines-filtered
+// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|BITINT_MAXWIDTH|_ATOMIC_LLONG_LOCK_FREE' > %t/i386-host-defines-filtered
 // RUN: %clang --cuda-device-only -nocudainc -nocudalib -target i386-unknown-linux-gnu -x cuda -E -dM -o - /dev/null \
 // RUN:   | grep -E 'define __[^ ]*(TYPE|MAX|SIZEOF|WIDTH)|define __CLANG_ATOMIC' \
-// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|_ATOMIC_LLONG_LOCK_FREE' > %t/i386-device-defines-filtered
+// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|BITINT_MAXWIDTH|_ATOMIC_LLONG_LOCK_FREE' > %t/i386-device-defines-filtered
 // RUN: diff %t/i386-host-defines-filtered %t/i386-device-defines-filtered
 
 // RUN: %clang --cuda-host-only -nocudainc -target x86_64-unknown-linux-gnu -x cuda -E -dM -o - /dev/null \
 // RUN:   | grep -E 'define __[^ ]*(TYPE|MAX|SIZEOF|WIDTH)|define __CLANG_ATOMIC' \
-// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE' > %t/x86_64-host-defines-filtered
+// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|BITINT_MAXWIDTH' > %t/x86_64-host-defines-filtered
 // RUN: %clang --cuda-device-only -nocudainc -nocudalib -target x86_64-unknown-linux-gnu -x cuda -E -dM -o - /dev/null \
 // RUN:   | grep -E 'define __[^ ]*(TYPE|MAX|SIZEOF|WIDTH)|define __CLANG_ATOMIC' \
-// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE' > %t/x86_64-device-defines-filtered
+// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|BITINT_MAXWIDTH' > %t/x86_64-device-defines-filtered
 // RUN: diff %t/x86_64-host-defines-filtered %t/x86_64-device-defines-filtered
 
 // RUN: %clang --cuda-host-only -nocudainc -target powerpc64-unknown-linux-gnu -x cuda -E -dM -o - /dev/null \
 // RUN:   | grep -E 'define __[^ ]*(TYPE|MAX|SIZEOF|WIDTH)|define __CLANG_ATOMIC' \
-// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE' > %t/powerpc64-host-defines-filtered
+// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|BITINT_MAXWIDTH' > %t/powerpc64-host-defines-filtered
 // RUN: %clang --cuda-device-only -nocudainc -nocudalib -target powerpc64-unknown-linux-gnu -x cuda -E -dM -o - /dev/null \
 // RUN:   | grep -E 'define __[^ ]*(TYPE|MAX|SIZEOF|WIDTH)|define __CLANG_ATOMIC' \
-// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE' > %t/powerpc64-device-defines-filtered
+// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|BITINT_MAXWIDTH' > %t/powerpc64-device-defines-filtered
 // RUN: diff %t/powerpc64-host-defines-filtered %t/powerpc64-device-defines-filtered
 
 // RUN: %clang --cuda-host-only -nocudainc -target i386-windows-msvc -x cuda -E -dM -o - /dev/null \
 // RUN:   | grep -E 'define __[^ ]*(TYPE|MAX|SIZEOF|WIDTH)|define __CLANG_ATOMIC' \
-// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|_ATOMIC_LLONG_LOCK_FREE' > %t/i386-msvc-host-defines-filtered
+// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|BITINT_MAXWIDTH|_ATOMIC_LLONG_LOCK_FREE' > %t/i386-msvc-host-defines-filtered
 // RUN: %clang --cuda-device-only -nocudainc -nocudalib -target i386-windows-msvc -x cuda -E -dM -o - /dev/null \
 // RUN:   | grep -E 'define __[^ ]*(TYPE|MAX|SIZEOF|WIDTH)|define __CLANG_ATOMIC' \
-// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|_ATOMIC_LLONG_LOCK_FREE' > %t/i386-msvc-device-defines-filtered
+// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|BITINT_MAXWIDTH|_ATOMIC_LLONG_LOCK_FREE' > %t/i386-msvc-device-defines-filtered
 // RUN: diff %t/i386-msvc-host-defines-filtered %t/i386-msvc-device-defines-filtered
 
 // RUN: %clang --cuda-host-only -nocudainc -target x86_64-windows-msvc -x cuda -E -dM -o - /dev/null \
 // RUN:   | grep -E 'define __[^ ]*(TYPE|MAX|SIZEOF|WIDTH)|define __CLANG_ATOMIC' \
-// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE' > %t/x86_64-msvc-host-defines-filtered
+// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|BITINT_MAXWIDTH' > %t/x86_64-msvc-host-defines-filtered
 // RUN: %clang --cuda-device-only -nocudainc -nocudalib -target x86_64-windows-msvc -x cuda -E -dM -o - /dev/null \
 // RUN:   | grep -E 'define __[^ ]*(TYPE|MAX|SIZEOF|WIDTH)|define __CLANG_ATOMIC' \
-// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE' > %t/x86_64-msvc-device-defines-filtered
+// RUN:   | grep -Ev '__LDBL|_LONG_DOUBLE|BITINT_MAXWIDTH' > %t/x86_64-msvc-device-defines-filtered
 // RUN: diff %t/x86_64-msvc-host-defines-filtered %t/x86_64-msvc-device-defines-filtered
diff --git a/clang/test/Sema/large-bit-int.c b/clang/test/Sema/large-bit-int.c
--- a/clang/test/Sema/large-bit-int.c
+++ b/clang/test/Sema/large-bit-int.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fexperimental-max-bitint-width=1024 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -triple aarch64-unknown-unknown -fexperimental-max-bitint-width=1024 -fsyntax-only -verify %s
 
 void f() {
   _Static_assert(__BITINT_MAXWIDTH__ == 1024, "Macro value is unexpected.");
diff --git a/clang/test/SemaCXX/ext-int.cpp b/clang/test/SemaCXX/ext-int.cpp
--- a/clang/test/SemaCXX/ext-int.cpp
+++ b/clang/test/SemaCXX/ext-int.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify %s -Wimplicit-int-conversion -Wno-unused -Wunevaluated-expression -triple x86_64-gnu-linux
+// RUN: %clang_cc1 -fsyntax-only -verify %s -Wimplicit-int-conversion -Wno-unused -Wunevaluated-expression -triple aarch64-unknown-unknown
 
 template<int Bounds>
 struct HasExtInt {