Win64: set FPU CW to 64-bit, set sprintf output format to 2 digits in…

… exponents
dlang · Jul 14, 2013 · 277da01 · 277da01
1 parent d46b4eb
commit 277da01
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diff --git a/src/core/stdc/stdio.d b/src/core/stdc/stdio.d
@@ -613,6 +613,9 @@ else version( Win64 )
     int   _vsnprintf(char* s, size_t n, in char* format, va_list arg);
     alias _vsnprintf vsnprintf;
 
+    uint _set_output_format(uint format);
+    enum _TWO_DIGIT_EXPONENT = 1;
+
     int _filbuf(FILE *fp);
     int _flsbuf(int c, FILE *fp);
 

diff --git a/src/rt/dmain2.d b/src/rt/dmain2.d
@@ -429,6 +429,20 @@ extern (C) int _d_run_main(int argc, char **argv, MainFunc mainFunc)
         stdin = &fp[0];
         stdout = &fp[1];
         stderr = &fp[2];
+
+        // ensure that sprintf generates only 2 digit exponent when writing floating point values
+        _set_output_format(_TWO_DIGIT_EXPONENT);
+
+        //_set_controlfp(_PC_64, _MCW_PC); // full precision for reals
+        asm
+        {
+            push    RAX;
+            fstcw   word ptr [RSP];
+            or      [RSP], 0b11_00_111111; // 11: use 64 bit extended-precision
+                                           // 111111: mask all FP exceptions
+            fldcw   word ptr [RSP];
+            pop     RAX;
+        }
     }
 
     _STI_monitor_staticctor();