[Flang][OpenMP][Runtime] Minor Flang runtime for OpenMP AMDGPU modifications (#152631)

We have some modifications downstream to compile the flang runtime for
amdgpu using clang OpenMP, some more hacky than others to workaround
(hopefully temporary) compiler issues. The additions here are the
non-hacky alterations.

Main changes:
* Create freestanding versions of memcpy, strlen and memmove, and
replace std:: references with these so that we can default to std:: when
it's available, or our own Flang implementation when it's not. * Wrap
more bits and pieces of the library in declare target wrappers (RT_*
macros). * Fix some warnings that'll pose issues with werror on, in this
case having the namespace infront of variables passed to templates.

Another minor issues that'll likely still pop up depending on the
program you're linking with is that abort will be undefined, it is
perhaps possible to solve it with a freestanding implementation as with
memcpy etc. but we end up with multiple definitions in this case. An
alternative is to create an empty extern "c" version (which can be empty
or forwrd on to the builtin).

Co-author: Dan Palermo [email protected]

Author: agozillon

flang-rt/include/flang-rt/runtime/buffer.h

@@ -158,8 +158,8 @@ template <typename STORE, std::size_t minBuffer = 65536> class FileFrame {
       // Avoid passing a null pointer, since it would result in an undefined
       // behavior.
       if (old != nullptr) {
-        std::memcpy(buffer_, old + start_, chunk);
-        std::memcpy(buffer_ + chunk, old, length_ - chunk);
+        runtime::memcpy(buffer_, old + start_, chunk);
+        runtime::memcpy(buffer_ + chunk, old, length_ - chunk);
         FreeMemory(old);
       }
       start_ = 0;

flang-rt/include/flang-rt/runtime/descriptor.h

@@ -32,8 +32,10 @@
 #include <cstdlib>
 #include <cstring>
 
+RT_OFFLOAD_VAR_GROUP_BEGIN
 /// Value used for asyncObject when no specific stream is specified.
 static constexpr std::int64_t *kNoAsyncObject = nullptr;
+RT_OFFLOAD_VAR_GROUP_END
 
 namespace Fortran::runtime {
 

flang-rt/include/flang-rt/runtime/format-implementation.h

@@ -49,7 +49,7 @@ RT_API_ATTRS FormatControl<CONTEXT>::FormatControl(const Terminator &terminator,
       SubscriptValue at[maxRank];
       formatDescriptor->GetLowerBounds(at);
       for (std::size_t j{0}; j < elements; ++j) {
-        std::memcpy(p, formatDescriptor->Element<char>(at), elementBytes);
+        runtime::memcpy(p, formatDescriptor->Element<char>(at), elementBytes);
         p += elementBytes;
         formatDescriptor->IncrementSubscripts(at);
       }

flang-rt/include/flang-rt/runtime/tools.h

@@ -560,9 +560,9 @@ RT_API_ATTRS void CopyAndPad(
       to[j] = static_cast<TO>(' ');
     }
   } else if (toChars <= fromChars) {
-    std::memcpy(to, from, toChars * sizeof(TO));
+    runtime::memcpy(to, from, toChars * sizeof(TO));
   } else {
-    std::memcpy(to, from, std::min(toChars, fromChars) * sizeof(TO));
+    runtime::memcpy(to, from, std::min(toChars, fromChars) * sizeof(TO));
     for (std::size_t j{fromChars}; j < toChars; ++j) {
       to[j] = static_cast<TO>(' ');
     }

flang-rt/lib/runtime/array-constructor.cpp

@@ -173,7 +173,7 @@ void RTDEF(PushArrayConstructorSimpleScalar)(
   AllocateOrReallocateVectorIfNeeded(vector, terminator, to.Elements(), 1);
   SubscriptValue subscript[1]{
       to.GetDimension(0).LowerBound() + vector.nextValuePosition};
-  std::memcpy(to.Element<char>(subscript), from, to.ElementBytes());
+  runtime::memcpy(to.Element<char>(subscript), from, to.ElementBytes());
   ++vector.nextValuePosition;
 }
 

flang-rt/lib/runtime/assign.cpp

@@ -288,7 +288,7 @@ RT_API_ATTRS int AssignTicket::Begin(WorkQueue &workQueue) {
     if (mustDeallocateLHS) {
       // Convert the LHS into a temporary, then make it look deallocated.
       toDeallocate_ = &tempDescriptor_.descriptor();
-      std::memcpy(
+      runtime::memcpy(
           reinterpret_cast<void *>(toDeallocate_), &to_, to_.SizeInBytes());
       to_.set_base_addr(nullptr);
       if (toDerived_ && (flags_ & NeedFinalization)) {
@@ -307,7 +307,7 @@ RT_API_ATTRS int AssignTicket::Begin(WorkQueue &workQueue) {
       auto descBytes{from_->SizeInBytes()};
       Descriptor &newFrom{tempDescriptor_.descriptor()};
       persist_ = true; // tempDescriptor_ state must outlive child tickets
-      std::memcpy(reinterpret_cast<void *>(&newFrom), from_, descBytes);
+      runtime::memcpy(reinterpret_cast<void *>(&newFrom), from_, descBytes);
       // Pretend the temporary descriptor is for an ALLOCATABLE
       // entity, otherwise, the Deallocate() below will not
       // free the descriptor memory.

flang-rt/lib/runtime/character.cpp

@@ -616,8 +616,8 @@ void RTDEF(CharacterConcatenate)(Descriptor &accumulator,
   from.GetLowerBounds(fromAt);
   for (; elements-- > 0;
        to += newBytes, p += oldBytes, from.IncrementSubscripts(fromAt)) {
-    std::memcpy(to, p, oldBytes);
-    std::memcpy(to + oldBytes, from.Element<char>(fromAt), fromBytes);
+    runtime::memcpy(to, p, oldBytes);
+    runtime::memcpy(to + oldBytes, from.Element<char>(fromAt), fromBytes);
   }
   FreeMemory(old);
 }
@@ -698,15 +698,15 @@ void RTDEF(CharacterCompare)(
 std::size_t RTDEF(CharacterAppend1)(char *lhs, std::size_t lhsBytes,
     std::size_t offset, const char *rhs, std::size_t rhsBytes) {
   if (auto n{std::min(lhsBytes - offset, rhsBytes)}) {
-    std::memcpy(lhs + offset, rhs, n);
+    runtime::memcpy(lhs + offset, rhs, n);
     offset += n;
   }
   return offset;
 }
 
 void RTDEF(CharacterPad1)(char *lhs, std::size_t bytes, std::size_t offset) {
   if (bytes > offset) {
-    std::memset(lhs + offset, ' ', bytes - offset);
+    runtime::memset(lhs + offset, ' ', bytes - offset);
   }
 }
 
@@ -838,7 +838,7 @@ void RTDEF(Repeat)(Descriptor &result, const Descriptor &string,
   }
   const char *from{string.OffsetElement()};
   for (char *to{result.OffsetElement()}; ncopies-- > 0; to += origBytes) {
-    std::memcpy(to, from, origBytes);
+    runtime::memcpy(to, from, origBytes);
   }
 }
 

flang-rt/lib/runtime/command.cpp

@@ -58,7 +58,7 @@ static std::int64_t StringLength(const char *string) {
 
 static void FillWithSpaces(const Descriptor &value, std::size_t offset = 0) {
   if (offset < value.ElementBytes()) {
-    std::memset(
+    runtime::memset(
         value.OffsetElement(offset), ' ', value.ElementBytes() - offset);
   }
 }

flang-rt/lib/runtime/copy.cpp

@@ -12,6 +12,8 @@
 #include "flang-rt/runtime/terminator.h"
 #include "flang-rt/runtime/type-info.h"
 #include "flang/Runtime/allocatable.h"
+#include "flang/Runtime/freestanding-tools.h"
+
 #include <cstring>
 
 namespace Fortran::runtime {
@@ -101,7 +103,7 @@ RT_API_ATTRS void CopyElement(const Descriptor &to, const SubscriptValue toAt[],
     char *toPtr{to.Element<char>(toAt)};
     char *fromPtr{from.Element<char>(fromAt)};
     RUNTIME_CHECK(terminator, to.ElementBytes() == from.ElementBytes());
-    std::memcpy(toPtr, fromPtr, to.ElementBytes());
+    runtime::memcpy(toPtr, fromPtr, to.ElementBytes());
     return;
   }
 
@@ -148,7 +150,7 @@ RT_API_ATTRS void CopyElement(const Descriptor &to, const SubscriptValue toAt[],
     // Moreover, if we came here from an Component::Genre::Data component,
     // all the per-element copies are redundant, because the parent
     // has already been copied as a whole.
-    std::memcpy(toPtr, fromPtr, curTo.ElementBytes());
+    runtime::memcpy(toPtr, fromPtr, curTo.ElementBytes());
     --elements;
     if (elements != 0) {
       currentCopy.IncrementSubscripts(terminator);

flang-rt/lib/runtime/derived.cpp

@@ -71,7 +71,7 @@ RT_API_ATTRS int InitializeTicket::Continue(WorkQueue &workQueue) {
       // Explicit initialization of data pointers and
       // non-allocatable non-automatic components
       std::size_t bytes{component_->SizeInBytes(instance_)};
-      std::memcpy(rawComponent, init, bytes);
+      runtime::memcpy(rawComponent, init, bytes);
     } else if (component_->genre() == typeInfo::Component::Genre::Pointer) {
       // Data pointers without explicit initialization are established
       // so that they are valid right-hand side targets of pointer
@@ -108,20 +108,20 @@ RT_API_ATTRS int InitializeTicket::Continue(WorkQueue &workQueue) {
             chunk = done;
           }
           char *uninitialized{rawInstance + done * *stride};
-          std::memcpy(uninitialized, rawInstance, chunk * *stride);
+          runtime::memcpy(uninitialized, rawInstance, chunk * *stride);
           done += chunk;
         }
       } else {
         for (std::size_t done{1}; done < elements_; ++done) {
           char *uninitialized{rawInstance + done * *stride};
-          std::memcpy(uninitialized, rawInstance, elementBytes);
+          runtime::memcpy(uninitialized, rawInstance, elementBytes);
         }
       }
     } else { // one at a time with subscription
       for (Elementwise::Advance(); !Elementwise::IsComplete();
           Elementwise::Advance()) {
         char *element{instance_.Element<char>(subscripts_)};
-        std::memcpy(element, rawInstance, elementBytes);
+        runtime::memcpy(element, rawInstance, elementBytes);
       }
     }
   }