[Libomptarget] Remove unnecessary CMake definition of endiannness

[jhuber6]

Summary:
This is needed for some definition in hsa.h that requires this to be
set for some architectures when it fails at autodetection. We only
really build libomptarget with gcc and clang which already provide
their own way of detecting this. Remove the unnecessary define and move
it into the source.

[llvmbot]

@llvm/pr-subscribers-backend-amdgpu

Author: Joseph Huber (jhuber6)

Changes

Summary:
This is needed for some definition in hsa.h that requires this to be
set for some architectures when it fails at autodetection. We only
really build libomptarget with gcc and clang which already provide
their own way of detecting this. Remove the unnecessary define and move
it into the source.

---

Full diff: https://github.com/llvm/llvm-project/pull/77205.diff

2 Files Affected:

• (modified) openmp/libomptarget/plugins-nextgen/amdgpu/CMakeLists.txt (-8)
• (modified) openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp (+12)

diff --git a/openmp/libomptarget/plugins-nextgen/amdgpu/CMakeLists.txt b/openmp/libomptarget/plugins-nextgen/amdgpu/CMakeLists.txt
index bbf8c0a50f85c4..68ce63467a6c81 100644
--- a/openmp/libomptarget/plugins-nextgen/amdgpu/CMakeLists.txt
+++ b/openmp/libomptarget/plugins-nextgen/amdgpu/CMakeLists.txt
@@ -35,14 +35,6 @@ add_definitions(-DTARGET_NAME=AMDGPU)
 # requires changing the original plugins.
 add_definitions(-DDEBUG_PREFIX="TARGET AMDGPU RTL")
 
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "(ppc64le)|(aarch64)$")
-   add_definitions(-DLITTLEENDIAN_CPU=1)
-endif()
-
-if(CMAKE_BUILD_TYPE MATCHES Debug)
-  add_definitions(-DDEBUG)
-endif()
-
 set(LIBOMPTARGET_DLOPEN_LIBHSA OFF)
 option(LIBOMPTARGET_FORCE_DLOPEN_LIBHSA "Build with dlopened libhsa" ${LIBOMPTARGET_DLOPEN_LIBHSA})
 
diff --git a/openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp b/openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp
index 0411c670133422..0eab5bc50c4aae 100644
--- a/openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp
+++ b/openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp
@@ -43,6 +43,18 @@
 #include "llvm/Support/Program.h"
 #include "llvm/Support/raw_ostream.h"
 
+#if !defined(__BYTE_ORDER__) || !defined(__ORDER_LITTLE_ENDIAN__) ||           \
+    !defined(__ORDER_BIG_ENDIAN__)
+#error "Missing preprocessor definitions for endianness detection."
+#endif
+
+// The HSA headers require these definitions.
+#if defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
+#define LITTLEENDIAN_CPU
+#elif defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+#define BIGENDIAN_CPU
+#endif
+
 #if defined(__has_include)
 #if __has_include("hsa/hsa.h")
 #include "hsa/hsa.h"