Difference between revisions of "Code Generation/Duplication of Floating Point Numbers on the Stack"

Revision as of 09:31, 9 May 2017

The following pure-Postfix program illustrates duplication of double-precision floating point numbers on the stack.

The C equivalent would be (roughly):

<c> int main() {

 extern void printd(double);
 double d, e;
 d = e = 3.3e-2;
 printd(d + e);
 return 0;

} </c>

Note that this program's code does not necessarily correspond to any particular code generator output.

Postfix code
<asm> -- generation of the "_main" function TEXT ALIGN GLOBAL _main, FUNC LABEL _main ENTER 16 ; d@-8 and e@-16 -- put double literal in RODATA RODATA ALIGN LABEL _L123 DOUBLE 3.3e-2 -- load literal onto stack TEXT ADDR _L123 DLOAD -- to perform the first assignment (to "e"), duplicate the value on the stack DDUP LOCAL -16 ; write value to "e" DSTORE -- to perform the second assignment (to "d"), duplicate the value on the stack DDUP LOCAL -8 ; write value to "d" DSTORE -- the assignments are an instruction trash the value left on the stack TRASH 8 -- now to perform the add operation LOCAL -8 DLOAD ; load "d" LOCAL -16 DLOAD ; load "e" DADD ; leaves result on the stack EXTERN printd CALL printd TRASH 8 ; argument value no longer needed INT 0 POP LEAVE RET </asm>

Assuming that the code above is in file dbl.pf, the following commands would compile and run the program:

pf2asm dbl.pf
yasm -felf dbl.asm
ld -o dbl dbl.o -lrts
./dbl

@@ Line 14: / Line 14: @@
 Note that this program's code does not necessarily correspond to any particular code generator output.
+{{CollapsedCode|Postfix code|
 <asm>
 ;;-- generation of the "_main" function
@@ Line 67: / Line 67: @@
 RET
 </asm>
+}}
 == Compiling and Running ==