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Avoiding conditional jumps platform independent

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lagprogramming:
   Is "ord(comparison)" returning 0 for false and 1 for true, no matter the target of the build?
As example, function Eof, which can be found in rtl/inc/text.inc, contains:


--- Code: ---     if TextRec(t).mode=fmOutput then
      InOutRes:=104
     else
      InOutRes:=103;
--- End code ---

   Can the above code be safely changed to "InOutRes:=103+ord(TextRec(t).mode=fmOutput);"?
   I'm thinking that who knows, maybe there are target CPUs where "ord(boolean_evaluation)" pascal code might return a value for true different than 1. I'm pretty sure false would return 0. I mention that "boolean_evaluation" is indeed a comparison, not a boolean function result, variable or something like that.

marcov:
Probably yes, but  "if TextRec(t).mode=fmOutput" as compare node might generate different code then ord(TextRec(t).mode=fmOutput)  (e.g. using flags instead having values 0 and 1 in registers)

Probably the best way is to do this optimizer level to transform such things in a target dependent manner.

Laksen:
marcov is right. The compiler should know best :)

For example on ARM, this:

--- Code: ---function test1(a: longint): longint;
begin
   if a = 123 then
      test1:=103
   else
      test1:=104;
end;

function test2(a: longint): longint;
begin
   test2:=a+ord(a=123);
end;

--- End code ---

Becomes:

--- Code: ---SYSTEM_$$_TEST1$LONGINT$$LONGINT:
cmp r0,#123
moveq r0,#103
movne r0,#104
bx r14

SYSTEM_$$_TEST2$LONGINT$$LONGINT:
cmp r0,#123
moveq r1,#1
movne r1,#0
add r0,r0,r1
bx r14

--- End code ---

lagprogramming:
@Laksen
What assembly code is produced for arm regarding the following two functions?


--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---function function1(var parameter:integer):boolean;beginif parameter<>0 then   begin   result:=true;   parameter:=0;   end else result:=false;end; function function2(var parameter:integer):boolean;beginresult:=parameter<>0;if result then parameter:=0;end;
Thank you

Thaddy:
simply compile with the -a option will give you the assembler output as <yourmodule>.s

for example: ppcrossarm -Tlinux -Mdelphi -O4  -CpARMV7A -s armasm.dpr (contains your functions)  gives you:


--- Code: ---# Begin asmlist al_procedures

.section .text.n_p$armasm_$$_function1$longint$$boolean
.balign 4
.globl P$ARMASM_$$_FUNCTION1$LONGINT$$BOOLEAN
.type P$ARMASM_$$_FUNCTION1$LONGINT$$BOOLEAN,#function
P$ARMASM_$$_FUNCTION1$LONGINT$$BOOLEAN:
mov r1,r0
ldr r0,[r1]
cmp r0,#0
movne r0,#1
movne r2,#0
strne r2,[r1]
moveq r0,#0
bx r14
.Le0:
.size P$ARMASM_$$_FUNCTION1$LONGINT$$BOOLEAN, .Le0 - P$ARMASM_$$_FUNCTION1$LONGINT$$BOOLEAN

.section .text.n_p$armasm_$$_function2$longint$$boolean
.balign 4
.globl P$ARMASM_$$_FUNCTION2$LONGINT$$BOOLEAN
.type P$ARMASM_$$_FUNCTION2$LONGINT$$BOOLEAN,#function
P$ARMASM_$$_FUNCTION2$LONGINT$$BOOLEAN:
mov r1,r0
ldr r0,[r1]
cmp r0,#0
movne r0,#1
# Peephole CmpMovMov - Removed redundant moveq
cmp r0,#0
movne r2,#0
strne r2,[r1]
bx r14
.Le1:
.size P$ARMASM_$$_FUNCTION2$LONGINT$$BOOLEAN, .Le1 - P$ARMASM_$$_FUNCTION2$LONGINT$$BOOLEAN

--- End code ---

As you can see: no branching at all.


 

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