Florian Klaempfl wrote:

Vincent Snijders wrote:

Hi,

Suppose I have the following code:

var
 a,b: dword;
 c: qword;

begin
 a := 10000000;
 b := 20000000;
 c := a * b;
 writeln(c);
end.

Now, although c is large enough to contain the result only the lower
dword is filled. I can force correct results by using c := qword(a) * b,
but the slow fpc_mul_qword is used.

The code generated for the above sample is:
# [16] c:=a*b;
   movl    U_P$PROJECT1_A,%edx
   movl    U_P$PROJECT1_B,%eax
   mull    %edx
   movl    $0,%edx
   movl    %eax,U_P$PROJECT1_C
   movl    %edx,U_P$PROJECT1_C+4

What I want is the above code, but without the "movl $0,%edx"
instruction. Is there a way to do this (wihtout using fpc_mul_qword).

Only assembler for now. Any suggestions how the compiler could be told
to generate such code?
IMHO it should automatically optimize expressions like:
 qword(a) * b
where a and b are dwords


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