libphobos: Backport minimal MinGW support patches.

Merges upstream druntime 1ca80e4e, phobos b5e9661a0.

Reviewed-on: https://github.com/dlang/druntime/pull/2587
	     https://github.com/dlang/phobos/pull/6981

From-SVN: r270638

libphobos/libdruntime/MERGE

@@ -1,4 +1,4 @@
-e03164b5259a9f116eb91dfa5a18c192fa72e575
+1ca80e4e0cf460575752a0c157ca52c184f4b982
 
 The first line of this file holds the git revision number of the last
 merge done from the dlang/druntime repository.

libphobos/libdruntime/core/stdc/stdio.d

@@ -1291,35 +1291,7 @@ size_t fwrite(scope const void* ptr, size_t size, size_t nmemb, FILE* stream);
     c_long ftell(FILE* stream);
 }
 
-version (MinGW)
+version (CRuntime_DigitalMars)
-{
-  // No unsafe pointer manipulation.
-  extern (D) @trusted
-  {
-    ///
-    void rewind()(FILE* stream)   { fseek(stream,0L,SEEK_SET); stream._flag = stream._flag & ~_IOERR; }
-    ///
-    pure void clearerr()(FILE* stream) { stream._flag = stream._flag & ~(_IOERR|_IOEOF); }
-    ///
-    pure int  feof()(FILE* stream)     { return stream._flag&_IOEOF; }
-    ///
-    pure int  ferror()(FILE* stream)   { return stream._flag&_IOERR; }
-  }
-  ///
-    int   __mingw_snprintf(scope char* s, size_t n, scope const char* fmt, ...);
-    ///
-    alias __mingw_snprintf _snprintf;
-    ///
-    alias __mingw_snprintf snprintf;
-
-    ///
-    int   __mingw_vsnprintf(scope char* s, size_t n, scope const char* format, va_list arg);
-    ///
-    alias __mingw_vsnprintf _vsnprintf;
-    ///
-    alias __mingw_vsnprintf vsnprintf;
-}
-else version (CRuntime_DigitalMars)
 {
   // No unsafe pointer manipulation.
   extern (D) @trusted
@@ -1362,6 +1334,23 @@ else version (CRuntime_Microsoft)
     pure int  fileno(FILE* stream);
   }
 
+  version (MinGW)
+  {
+    int   __mingw_snprintf(scope char* s, size_t n, scope const char* fmt, ...);
+    ///
+    alias __mingw_snprintf _snprintf;
+    ///
+    alias __mingw_snprintf snprintf;
+
+    ///
+    int   __mingw_vsnprintf(scope char* s, size_t n, scope const char* format, va_list arg);
+    ///
+    alias __mingw_vsnprintf _vsnprintf;
+    ///
+    alias __mingw_vsnprintf vsnprintf;
+  }
+  else
+  {
     ///
     int _snprintf(scope char* s, size_t n, scope const char* format, ...);
     ///
@@ -1371,6 +1360,7 @@ else version (CRuntime_Microsoft)
     int _vsnprintf(scope char* s, size_t n, scope const char* format, va_list arg);
     ///
     int  vsnprintf(scope char* s, size_t n, scope const char* format, va_list arg);
+  }
 
     ///
     int _fputc_nolock(int c, FILE *fp);

libphobos/libdruntime/core/sys/windows/dll.d

@@ -328,7 +328,9 @@ public:
  */
 bool dll_fixTLS( HINSTANCE hInstance, void* tlsstart, void* tlsend, void* tls_callbacks_a, int* tlsindex ) nothrow
 {
-    version (Win64)
+    version (GNU_EMUTLS)
+        return true;
+    else version (Win64)
         return true;                // fixed
     else version (Win32)
     {

libphobos/libdruntime/core/thread.d

@@ -49,9 +49,17 @@ version (Solaris)
     import core.sys.solaris.sys.types;
 }
 
-// this should be true for most architectures
+version (GNU)
-version (GNU_StackGrowsDown)
+{
+    import gcc.builtins;
+    version (GNU_StackGrowsDown)
+        version = StackGrowsDown;
+}
+else
+{
+    // this should be true for most architectures
     version = StackGrowsDown;
+}
 
 /**
  * Returns the process ID of the calling process, which is guaranteed to be
@@ -301,11 +309,6 @@ else version (Posix)
             import core.sys.darwin.pthread : pthread_mach_thread_np;
         }
 
-        version (GNU)
-        {
-            import gcc.builtins;
-        }
-
         //
         // Entry point for POSIX threads
         //

libphobos/libdruntime/rt/dmain2.d

@@ -340,7 +340,15 @@ extern (C) int _d_run_main(int argc, char **argv, MainFunc mainFunc)
     version (CRuntime_Microsoft)
     {
         // enable full precision for reals
-        version (Win64)
+        version (GNU)
+        {
+            size_t fpu_cw;
+            asm { "fstcw %0" : "=m" (fpu_cw); }
+            fpu_cw |= 0b11_00_111111;  // 11: use 64 bit extended-precision
+                                       // 111111: mask all FP exceptions
+            asm { "fldcw %0" : "=m" (fpu_cw); }
+        }
+        else version (Win64)
             asm
             {
                 push    RAX;

libphobos/src/MERGE

@@ -1,4 +1,4 @@
-b538f758a4d274b64751f80564b0207845cd018c
+b5e9661a089b6514e01fa5195c0f2bc9cc06eddd
 
 The first line of this file holds the git revision number of the last
 merge done from the dlang/phobos repository.

libphobos/src/std/math.d

@@ -174,6 +174,12 @@ else version (D_InlineAsm_X86_64)
     version = InlineAsm_X86_Any;
 }
 
+version (CRuntime_Microsoft)
+{
+    version (InlineAsm_X86_Any)
+        version = MSVC_InlineAsm;
+}
+
 version (X86_64) version = StaticallyHaveSSE;
 version (X86) version (OSX) version = StaticallyHaveSSE;
 
@@ -3692,7 +3698,7 @@ real logb(real x) @trusted nothrow @nogc
             ret                         ;
         }
     }
-    else version (CRuntime_Microsoft)
+    else version (MSVC_InlineAsm)
     {
         asm pure nothrow @nogc
         {
@@ -3979,7 +3985,7 @@ real ceil(real x) @trusted pure nothrow @nogc
             ret                         ;
         }
     }
-    else version (CRuntime_Microsoft)
+    else version (MSVC_InlineAsm)
     {
         short cw;
         asm pure nothrow @nogc
@@ -4107,7 +4113,7 @@ real floor(real x) @trusted pure nothrow @nogc
             ret                         ;
         }
     }
-    else version (CRuntime_Microsoft)
+    else version (MSVC_InlineAsm)
     {
         short cw;
         asm pure nothrow @nogc
@@ -4607,7 +4613,7 @@ real trunc(real x) @trusted nothrow @nogc
             ret                         ;
         }
     }
-    else version (CRuntime_Microsoft)
+    else version (MSVC_InlineAsm)
     {
         short cw;
         asm pure nothrow @nogc