Float compare bug?

[John Gonzaga]

Hi,

I'm having a problem with the greater or equal operator (>=) with float 
arguments. I'm using

	GCC 3.3.2
	newlib 1.12.0
	ARM7TDMI-S processor
	little endian mode

It seems that:

	float test = 7.2;
	if(test >= 7.2)

the condition will return false. I have this snippet of code to try to 
figure out what's going on:

	void App::Initialize()
	{
		float test = 7.2;
		if(test >= 7.2) asm("mov r1, #0");
		else asm("mov r1, #1");	
	}

this is the code dump ...

	0000034c <_ZN3App10InitializeEv>:
	     34c:	e1a0c00d 	mov	ip, sp
	     350:	e92dd800 	stmdb	sp!, {fp, ip, lr, pc}
	     354:	e28f002c 	add	r0, pc, #44	; 0x2c
	     358:	e8900003 	ldmia	r0, {r0, r1}
	     35c:	e24cb004 	sub	fp, ip, #4	; 0x4
	     360:	e28f2028 	add	r2, pc, #40	; 0x28
	     364:	e892000c 	ldmia	r2, {r2, r3}
	     368:	eb003457 	bl	d4cc <__gedf2>
	     36c:	e3500000 	cmp	r0, #0	; 0x0
	     370:	ba000002 	blt	380 <_ZN3App10InitializeEv+0x34>
	     374:	e3a01000 	mov	r1, #0	; 0x0
	     378:	e91b6800 	ldmdb	fp, {fp, sp, lr}
	     37c:	e12fff1e 	bx	lr
	     380:	e3a01001 	mov	r1, #1	; 0x1
	     384:	eafffffb 	b	378 <_ZN3App10InitializeEv+0x2c>
	     388:	401ccccc 	andmis	ip, ip, ip, asr #25
	     38c:	c0000000 	andgt	r0, r0, r0
	     390:	401ccccc 	andmis	ip, ip, ip, asr #25
	     394:	cccccccd 	stcgtl	12, cr12, [ip], #820

I set a breakpoint on address 368 then dump the registers.

          User     FIQ     Superv   Abort     IRQ      Undef
GPR00: 401ccccc 401ccccc 401ccccc 401ccccc 401ccccc 401ccccc
GPR01: c0000000 c0000000 c0000000 c0000000 c0000000 c0000000
GPR02: 401ccccc 401ccccc 401ccccc 401ccccc 401ccccc 401ccccc
GPR03: cccccccd cccccccd cccccccd cccccccd cccccccd cccccccd
GPR04: e002c000 e002c000 e002c000 e002c000 e002c000 e002c000
GPR05: 7ffffd24 7ffffd24 7ffffd24 7ffffd24 7ffffd24 7ffffd24
GPR06: 40000128 40000128 40000128 40000128 40000128 40000128
GPR07: 00000000 00000000 00000000 00000000 00000000 00000000
GPR08: 08000800 cbeb48f7 08000800 08000800 08000800 08000800
GPR09: 08000800 6f68fdad 08000800 08000800 08000800 08000800
GPR10: 08000800 a0700340 08000800 08000800 08000800 08000800
GPR11: 4000ee30 4000fec8 4000ee30 4000ee30 4000ee30 4000ee30
GPR12: 4000ee34 4000fecc 4000ee34 4000ee34 4000ee34 4000ee34
GPR13: eb20475f 4000ff00 4000ee24 f0aef6f0 4000f700 40001800
GPR14: 7700403b 00004bb8 0000700c 0000007c 00000090 7fffe258
PC   : 00000368
CPSR : 20000013
SPSR :          00000010 00000010 00000010 80000013 00000010

Looking at the code dump r0 and r2 has the arguments for the compare 
function (am I correct?),
which are both 0x401CCCCC. I then set the breakpoint again on 36C and 
here's the register dump

          User     FIQ     Superv   Abort     IRQ      Undef
GPR00: ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff
GPR01: 00000000 00000000 00000000 00000000 00000000 00000000
GPR02: 1ccccccc 1ccccccc 1ccccccc 1ccccccc 1ccccccc 1ccccccc
GPR03: 1cccccc0 1cccccc0 1cccccc0 1cccccc0 1cccccc0 1cccccc0
GPR04: e002c000 e002c000 e002c000 e002c000 e002c000 e002c000
GPR05: 7ffffd24 7ffffd24 7ffffd24 7ffffd24 7ffffd24 7ffffd24
GPR06: 40000128 40000128 40000128 40000128 40000128 40000128
GPR07: 00000000 00000000 00000000 00000000 00000000 00000000
GPR08: 08000800 cbeb48f7 08000800 08000800 08000800 08000800
GPR09: 08000800 6f68fdad 08000800 08000800 08000800 08000800
GPR10: 08000800 a0700340 08000800 08000800 08000800 08000800
GPR11: 4000ee30 4000fec8 4000ee30 4000ee30 4000ee30 4000ee30
GPR12: 4000edf8 4000fecc 4000edf8 4000edf8 4000edf8 4000edf8
GPR13: eb20475f 4000ff00 4000ee24 f0aef6f0 4000f700 40001800
GPR14: 7700403b 00004bb8 0000e2b0 0000007c 00000090 7fffe258
PC   : 0000036c
CPSR : 60000013
SPSR :          00000010 00000010 00000010 20000013 00000010

r0 contains 0xFFFFFFFF indicating false. To make this work properly,
I just changed the code to (cast on the constant):

	void App::Initialize()
	{
		float test = 7.2;
		if(test >= (float)7.2) asm("mov r1, #0");
		else asm("mov r1, #1");	
	}

Now do I have to cast all my constant floats? Is this a bug? Thanks.

-John G-







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