[CMake] [Clang] Add CMake build option to specify long double format on PowerPC

[qiucf]

Summary

This method introduces new CMake variable PPC_LINUX_DEFAULT_IEEELONGDOUBLE (false by default) to enable fp128 as default long double format.

We need to make some tests explicitly set long double type, otherwise they fail in either config.

[nemanjai]

It is probably not worth the effort since there won't be that many test cases that test the front end's IR generation for long double, but there should be a way to set up lit to know the default through its configuration files.

[nemanjai]

clang/CMakeLists.txt

240

Do we need any error checking here? What happens if someone erroneously sets this on an AIX build (or big endian Linux, FreeBSD, etc.)?

[jsji]

In D118110#3269450, @nemanjai wrote:

It is probably not worth the effort since there won't be that many test cases that test the front end's IR generation for long double, but there should be a way to set up lit to know the default through its configuration files.

Yes, that is not a must for now, but we should try to do it .

There's one thing uncertain: whether this config only applies to ppc64le?

Let us apply it to ppc64le only for now.

clang/CMakeLists.txt

240

How about CLANG_DEFAULT_IEEELONGDOUBLE_ON_PPC_LINUX similar to CLANG_DEFAULT_PIE_ON_LINUX?

clang/include/clang/Driver/ToolChain.h

413

defaultToIEEELongDouble?

clang/lib/Driver/ToolChain.cpp

113

Check OS here ?

eg: CLANG_DEFAULT_IEEELONGDOUBLE_ON_PPC_LINUX && OS.Linux()

[qiucf]

It is probably not worth the effort since there won't be that many test cases that test the front end's IR generation for long double, but there should be a way to set up lit to know the default through its configuration files.

Yes, lit doesn't know about it. But lit can't do things in IR test like #ifdef in C nor change default semantics of clang, so it seems not able to help in such cases.

[jsji]

LGTM.

clang/CMakeLists.txt

 set(DEFAULT_SYSROOT "" CACHE STRING
   "Default <path> to all compiler invocations for --sysroot=<path>." )
 
 set(ENABLE_LINKER_BUILD_ID OFF CACHE BOOL "pass --build-id to ld")
 
 set(ENABLE_X86_RELAX_RELOCATIONS ON CACHE BOOL
     "enable x86 relax relocations by default")
 
+set(PPC_LINUX_DEFAULT_IEEELONGDOUBLE OFF CACHE BOOL
+    "Enable IEEE binary128 as default long double format on PowerPC Linux.")
+
 set(CLANG_SPAWN_CC1 OFF CACHE BOOL
     "Whether clang should use a new process for the CC1 invocation")
 
 option(CLANG_DEFAULT_PIE_ON_LINUX "Default to -fPIE and -pie on Linux" OFF)
 
 # TODO: verify the values against LangStandards.def?
 set(CLANG_DEFAULT_STD_C "" CACHE STRING
   "Default standard to use for C/ObjC code (IDENT from LangStandards.def, empty for platform default)")

clang/include/clang/Config/config.h.cmake

 #cmakedefine HOST_LINK_VERSION "${HOST_LINK_VERSION}"
 
 /* pass --build-id to ld */
 #cmakedefine ENABLE_LINKER_BUILD_ID
 
 /* enable x86 relax relocations by default */
 #cmakedefine01 ENABLE_X86_RELAX_RELOCATIONS
 
+/* Enable IEEE binary128 as default long double format on PowerPC Linux. */
+#cmakedefine01 PPC_LINUX_DEFAULT_IEEELONGDOUBLE
+
 /* Enable each functionality of modules */
 #cmakedefine01 CLANG_ENABLE_ARCMT
 #cmakedefine01 CLANG_ENABLE_OBJC_REWRITER
 #cmakedefine01 CLANG_ENABLE_STATIC_ANALYZER
 
 /* Spawn a new process clang.exe for the CC1 tool invocation, when necessary */
 #cmakedefine01 CLANG_SPAWN_CC1
 
 #endif

clang/include/clang/Driver/ToolChain.h

public:
 
   /// UseObjCMixedDispatchDefault - When using non-legacy dispatch, should the
   /// mixed dispatch method be used?
   virtual bool UseObjCMixedDispatch() const { return false; }
 
   /// Check whether to enable x86 relax relocations by default.
   virtual bool useRelaxRelocations() const;
 
+  /// Check whether use IEEE binary128 as long double format by default.
+  bool defaultToIEEELongDouble() const;
+
   /// GetDefaultStackProtectorLevel - Get the default stack protector level for
   /// this tool chain.
   virtual LangOptions::StackProtectorMode
   GetDefaultStackProtectorLevel(bool KernelOrKext) const {
     return LangOptions::SSPOff;
   }
 
   /// Get the default trivial automatic variable initialization.

clang/lib/Driver/ToolChain.cpp

return Args.hasFlag(options::OPT_fintegrated_as,
                       options::OPT_fno_integrated_as,
                       IsIntegratedAssemblerDefault());
 }
 
 bool ToolChain::useRelaxRelocations() const {
   return ENABLE_X86_RELAX_RELOCATIONS;
 }
 
+bool ToolChain::defaultToIEEELongDouble() const {
+  return PPC_LINUX_DEFAULT_IEEELONGDOUBLE && getTriple().isOSLinux();
+}
+
 SanitizerArgs
 ToolChain::getSanitizerArgs(const llvm::opt::ArgList &JobArgs) const {
   SanitizerArgs SanArgs(*this, JobArgs, !SanitizerArgsChecked);
   SanitizerArgsChecked = true;
   return SanArgs;
 }
 
 const XRayArgs& ToolChain::getXRayArgs() const {

clang/lib/Driver/ToolChains/Clang.cpp

if (T.isOSBinFormatELF()) {
     case llvm::Triple::ppc64le:
       ABIName = "elfv2";
       break;
     default:
       break;
     }
   }
 
-  bool IEEELongDouble = false;
+  bool IEEELongDouble = getToolChain().defaultToIEEELongDouble();
   for (const Arg *A : Args.filtered(options::OPT_mabi_EQ)) {
     StringRef V = A->getValue();
     if (V == "ieeelongdouble")
       IEEELongDouble = true;
     else if (V == "ibmlongdouble")
       IEEELongDouble = false;
     else if (V != "altivec")
       // The ppc64 linux abis are all "altivec" abis by default. Accept and ignore

clang/test/Analysis/builtin_signbit.cpp

-// RUN: %clang -target powerpc-linux-gnu     -emit-llvm -S -O0 %s -o - | FileCheck %s --check-prefix=CHECK-BE --check-prefix=CHECK
-// RUN: %clang -target powerpc64-linux-gnu   -emit-llvm -S -O0 %s -o - | FileCheck %s --check-prefix=CHECK-BE --check-prefix=CHECK
-// RUN: %clang -target powerpc64le-linux-gnu -emit-llvm -S -O0 %s -o - | FileCheck %s --check-prefix=CHECK-LE --check-prefix=CHECK
+// RUN: %clang -target powerpc-linux-gnu -emit-llvm -S -mabi=ibmlongdouble \
+// RUN:   -O0 %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-BE
+// RUN: %clang -target powerpc64-linux-gnu -emit-llvm -S -mabi=ibmlongdouble \
+// RUN:   -O0 %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-BE
+// RUN: %clang -target powerpc64le-linux-gnu -emit-llvm -S -mabi=ibmlongdouble \
+// RUN:   -O0 %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-LE
 
 bool b;
 double d = -1.0;
 long double ld = -1.0L;
 void test_signbit()
 {
   b = __builtin_signbit(1.0L);
   // CHECK: i128

clang/test/Driver/ppc-abi.c

 // RUN: %clang -target powerpc64le-linux-gnu %s -mabi=elfv1 -mabi=ieeelongdouble -### 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHECK-ELFv1-IEEE %s
 // RUN: %clang -target powerpc64le-linux-gnu %s -mabi=elfv2 -mabi=elfv1 -mabi=ibmlongdouble -mabi=ieeelongdouble -### 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHECK-ELFv1-IEEE %s
 
 // CHECK-ELFv1-IEEE: "-mabi=ieeelongdouble"
 // CHECK-ELFv1-IEEE: "-target-abi" "elfv1"
 
-// Check -mabi=ibmlongdouble is the default.
-// RUN: %clang -target powerpc64le-linux-gnu %s -### 2>&1 \
-// RUN:   | FileCheck -check-prefix=CHECK-ELFv2-IBM128 %s
 // RUN: %clang -target powerpc64le-linux-gnu %s -mabi=ibmlongdouble -### 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHECK-ELFv2-IBM128 %s
 
 // CHECK-ELFv2-IBM128-NOT: "-mabi=ieeelongdouble"
 // CHECK-ELFv2-IBM128: "-target-abi" "elfv2"