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linux_dsm_epyc7002/arch/x86/math-emu/reg_compare.c
Arnd Bergmann 75e2f0a6b1 x86/fpu/math-emu: Fix possible uninitialized variable use 
When building the kernel with "make EXTRA_CFLAGS=...", this overrides
the "PARANOID" preprocessor macro defined in arch/x86/math-emu/Makefile,
and we run into a build warning:

  arch/x86/math-emu/reg_compare.c: In function ‘compare_i_st_st’:
  arch/x86/math-emu/reg_compare.c:254:6: error: ‘f’ may be used uninitialized in this function [-Werror=maybe-uninitialized]

This fixes the implementation to work correctly even without the PARANOID
flag, and also fixes the Makefile to not use the EXTRA_CFLAGS variable
but instead use the ccflags-y variable in the Makefile that is meant
for this purpose.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Bill Metzenthen <billm@melbpc.org.au>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170719125310.2487451-3-arnd@arndb.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-07-20 10:46:24 +02:00

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/*---------------------------------------------------------------------------+
| reg_compare.c |
| |
| Compare two floating point registers |
| |
| Copyright (C) 1992,1993,1994,1997 |
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
| E-mail billm@suburbia.net |
| |
| |
+---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------+
| compare() is the core FPU_REG comparison function |
+---------------------------------------------------------------------------*/
#include "fpu_system.h"
#include "exception.h"
#include "fpu_emu.h"
#include "control_w.h"
#include "status_w.h"
static int compare(FPU_REG const *b, int tagb)
{
int diff, exp0, expb;
u_char st0_tag;
FPU_REG *st0_ptr;
FPU_REG x, y;
u_char st0_sign, signb = getsign(b);
st0_ptr = &st(0);
st0_tag = FPU_gettag0();
st0_sign = getsign(st0_ptr);
if (tagb == TAG_Special)
tagb = FPU_Special(b);
if (st0_tag == TAG_Special)
st0_tag = FPU_Special(st0_ptr);
if (((st0_tag != TAG_Valid) && (st0_tag != TW_Denormal))
|| ((tagb != TAG_Valid) && (tagb != TW_Denormal))) {
if (st0_tag == TAG_Zero) {
if (tagb == TAG_Zero)
return COMP_A_eq_B;
if (tagb == TAG_Valid)
return ((signb ==
SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
if (tagb == TW_Denormal)
return ((signb ==
SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
| COMP_Denormal;
} else if (tagb == TAG_Zero) {
if (st0_tag == TAG_Valid)
return ((st0_sign ==
SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
if (st0_tag == TW_Denormal)
return ((st0_sign ==
SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
| COMP_Denormal;
}
if (st0_tag == TW_Infinity) {
if ((tagb == TAG_Valid) || (tagb == TAG_Zero))
return ((st0_sign ==
SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
else if (tagb == TW_Denormal)
return ((st0_sign ==
SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
| COMP_Denormal;
else if (tagb == TW_Infinity) {
/* The 80486 book says that infinities can be equal! */
return (st0_sign == signb) ? COMP_A_eq_B :
((st0_sign ==
SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
}
/* Fall through to the NaN code */
} else if (tagb == TW_Infinity) {
if ((st0_tag == TAG_Valid) || (st0_tag == TAG_Zero))
return ((signb ==
SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
if (st0_tag == TW_Denormal)
return ((signb ==
SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
| COMP_Denormal;
/* Fall through to the NaN code */
}
/* The only possibility now should be that one of the arguments
is a NaN */
if ((st0_tag == TW_NaN) || (tagb == TW_NaN)) {
int signalling = 0, unsupported = 0;
if (st0_tag == TW_NaN) {
signalling =
(st0_ptr->sigh & 0xc0000000) == 0x80000000;
unsupported = !((exponent(st0_ptr) == EXP_OVER)
&& (st0_ptr->
sigh & 0x80000000));
}
if (tagb == TW_NaN) {
signalling |=
(b->sigh & 0xc0000000) == 0x80000000;
unsupported |= !((exponent(b) == EXP_OVER)
&& (b->sigh & 0x80000000));
}
if (signalling || unsupported)
return COMP_No_Comp | COMP_SNaN | COMP_NaN;
else
/* Neither is a signaling NaN */
return COMP_No_Comp | COMP_NaN;
}
EXCEPTION(EX_Invalid);
}
if (st0_sign != signb) {
return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
| (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
COMP_Denormal : 0);
}
if ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) {
FPU_to_exp16(st0_ptr, &x);
FPU_to_exp16(b, &y);
st0_ptr = &x;
b = &y;
exp0 = exponent16(st0_ptr);
expb = exponent16(b);
} else {
exp0 = exponent(st0_ptr);
expb = exponent(b);
}
#ifdef PARANOID
if (!(st0_ptr->sigh & 0x80000000))
EXCEPTION(EX_Invalid);
if (!(b->sigh & 0x80000000))
EXCEPTION(EX_Invalid);
#endif /* PARANOID */
diff = exp0 - expb;
if (diff == 0) {
diff = st0_ptr->sigh - b->sigh; /* Works only if ms bits are
identical */
if (diff == 0) {
diff = st0_ptr->sigl > b->sigl;
if (diff == 0)
diff = -(st0_ptr->sigl < b->sigl);
}
}
if (diff > 0) {
return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
| (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
COMP_Denormal : 0);
}
if (diff < 0) {
return ((st0_sign == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
| (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
COMP_Denormal : 0);
}
return COMP_A_eq_B
| (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
COMP_Denormal : 0);
}
/* This function requires that st(0) is not empty */
int FPU_compare_st_data(FPU_REG const *loaded_data, u_char loaded_tag)
{
int f, c;
c = compare(loaded_data, loaded_tag);
if (c & COMP_NaN) {
EXCEPTION(EX_Invalid);
f = SW_C3 | SW_C2 | SW_C0;
} else
switch (c & 7) {
case COMP_A_lt_B:
f = SW_C0;
break;
case COMP_A_eq_B:
f = SW_C3;
break;
case COMP_A_gt_B:
f = 0;
break;
case COMP_No_Comp:
f = SW_C3 | SW_C2 | SW_C0;
break;
default:
#ifdef PARANOID
EXCEPTION(EX_INTERNAL | 0x121);
#endif /* PARANOID */
f = SW_C3 | SW_C2 | SW_C0;
break;
}
setcc(f);
if (c & COMP_Denormal) {
return denormal_operand() < 0;
}
return 0;
}
static int compare_st_st(int nr)
{
int f, c;
FPU_REG *st_ptr;
if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
setcc(SW_C3 | SW_C2 | SW_C0);
/* Stack fault */
EXCEPTION(EX_StackUnder);
return !(control_word & CW_Invalid);
}
st_ptr = &st(nr);
c = compare(st_ptr, FPU_gettagi(nr));
if (c & COMP_NaN) {
setcc(SW_C3 | SW_C2 | SW_C0);
EXCEPTION(EX_Invalid);
return !(control_word & CW_Invalid);
} else
switch (c & 7) {
case COMP_A_lt_B:
f = SW_C0;
break;
case COMP_A_eq_B:
f = SW_C3;
break;
case COMP_A_gt_B:
f = 0;
break;
case COMP_No_Comp:
f = SW_C3 | SW_C2 | SW_C0;
break;
default:
#ifdef PARANOID
EXCEPTION(EX_INTERNAL | 0x122);
#endif /* PARANOID */
f = SW_C3 | SW_C2 | SW_C0;
break;
}
setcc(f);
if (c & COMP_Denormal) {
return denormal_operand() < 0;
}
return 0;
}
static int compare_i_st_st(int nr)
{
int f, c;
FPU_REG *st_ptr;
if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
FPU_EFLAGS |= (X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF);
/* Stack fault */
EXCEPTION(EX_StackUnder);
return !(control_word & CW_Invalid);
}
partial_status &= ~SW_C0;
st_ptr = &st(nr);
c = compare(st_ptr, FPU_gettagi(nr));
if (c & COMP_NaN) {
FPU_EFLAGS |= (X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF);
EXCEPTION(EX_Invalid);
return !(control_word & CW_Invalid);
}
switch (c & 7) {
case COMP_A_lt_B:
f = X86_EFLAGS_CF;
break;
case COMP_A_eq_B:
f = X86_EFLAGS_ZF;
break;
case COMP_A_gt_B:
f = 0;
break;
case COMP_No_Comp:
f = X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF;
break;
default:
#ifdef PARANOID
EXCEPTION(EX_INTERNAL | 0x122);
#endif /* PARANOID */
f = 0;
break;
}
FPU_EFLAGS = (FPU_EFLAGS & ~(X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF)) | f;
if (c & COMP_Denormal) {
return denormal_operand() < 0;
}
return 0;
}
static int compare_u_st_st(int nr)
{
int f = 0, c;
FPU_REG *st_ptr;
if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
setcc(SW_C3 | SW_C2 | SW_C0);
/* Stack fault */
EXCEPTION(EX_StackUnder);
return !(control_word & CW_Invalid);
}
st_ptr = &st(nr);
c = compare(st_ptr, FPU_gettagi(nr));
if (c & COMP_NaN) {
setcc(SW_C3 | SW_C2 | SW_C0);
if (c & COMP_SNaN) { /* This is the only difference between
un-ordered and ordinary comparisons */
EXCEPTION(EX_Invalid);
return !(control_word & CW_Invalid);
}
return 0;
} else
switch (c & 7) {
case COMP_A_lt_B:
f = SW_C0;
break;
case COMP_A_eq_B:
f = SW_C3;
break;
case COMP_A_gt_B:
f = 0;
break;
case COMP_No_Comp:
f = SW_C3 | SW_C2 | SW_C0;
break;
#ifdef PARANOID
default:
EXCEPTION(EX_INTERNAL | 0x123);
f = SW_C3 | SW_C2 | SW_C0;
break;
#endif /* PARANOID */
}
setcc(f);
if (c & COMP_Denormal) {
return denormal_operand() < 0;
}
return 0;
}
static int compare_ui_st_st(int nr)
{
int f = 0, c;
FPU_REG *st_ptr;
if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
FPU_EFLAGS |= (X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF);
/* Stack fault */
EXCEPTION(EX_StackUnder);
return !(control_word & CW_Invalid);
}
partial_status &= ~SW_C0;
st_ptr = &st(nr);
c = compare(st_ptr, FPU_gettagi(nr));
if (c & COMP_NaN) {
FPU_EFLAGS |= (X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF);
if (c & COMP_SNaN) { /* This is the only difference between
un-ordered and ordinary comparisons */
EXCEPTION(EX_Invalid);
return !(control_word & CW_Invalid);
}
return 0;
}
switch (c & 7) {
case COMP_A_lt_B:
f = X86_EFLAGS_CF;
break;
case COMP_A_eq_B:
f = X86_EFLAGS_ZF;
break;
case COMP_A_gt_B:
f = 0;
break;
case COMP_No_Comp:
f = X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF;
break;
#ifdef PARANOID
default:
EXCEPTION(EX_INTERNAL | 0x123);
f = 0;
break;
#endif /* PARANOID */
}
FPU_EFLAGS = (FPU_EFLAGS & ~(X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF)) | f;
if (c & COMP_Denormal) {
return denormal_operand() < 0;
}
return 0;
}
/*---------------------------------------------------------------------------*/
void fcom_st(void)
{
/* fcom st(i) */
compare_st_st(FPU_rm);
}
void fcompst(void)
{
/* fcomp st(i) */
if (!compare_st_st(FPU_rm))
FPU_pop();
}
void fcompp(void)
{
/* fcompp */
if (FPU_rm != 1) {
FPU_illegal();
return;
}
if (!compare_st_st(1))
poppop();
}
void fucom_(void)
{
/* fucom st(i) */
compare_u_st_st(FPU_rm);
}
void fucomp(void)
{
/* fucomp st(i) */
if (!compare_u_st_st(FPU_rm))
FPU_pop();
}
void fucompp(void)
{
/* fucompp */
if (FPU_rm == 1) {
if (!compare_u_st_st(1))
poppop();
} else
FPU_illegal();
}
/* P6+ compare-to-EFLAGS ops */
void fcomi_(void)
{
/* fcomi st(i) */
compare_i_st_st(FPU_rm);
}
void fcomip(void)
{
/* fcomip st(i) */
if (!compare_i_st_st(FPU_rm))
FPU_pop();
}
void fucomi_(void)
{
/* fucomi st(i) */
compare_ui_st_st(FPU_rm);
}
void fucomip(void)
{
/* fucomip st(i) */
if (!compare_ui_st_st(FPU_rm))
FPU_pop();
}
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