I put the code you posted into a small Keil project file, albeit with a few more essential lines:

#include <c8051f020.h>                 	// SFR declarations

void main(void)
{
	float a;

	a=5.34;
	if(a>1.2)
		P1=20;
	else
		P1=10;

	while(1);
}

I found it to compile just fine. In addition I stepped the code through the Keil simulation mode debugger and the P1=20; clause of the if/else was executed just like one would expect.

BTW. Floating point on MCUs can sometimes be a bad idea. Note that this small program compiled to a whopping 167 bytes. For sure a small portion of the code was the C-Startup code but the main code lines are only a few bytes (43 to be exact) with a huge portion (109 bytes) taken up by the C?FPCMP3 routine which is used to compare variable a to 1.2.

Michael Karas