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target/i386: fix floating-point load-constant rounding

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The implementations of the fldl2t, fldl2e, fldpi, fldlg2 and fldln2
instructions load fixed constants independent of the rounding mode.
Fix them to load a value correctly rounded for the current rounding
mode (but always rounded to 64-bit precision independent of the
precision control, and without setting "inexact") as specified.

Backports commit 80b4008c805ebcfd4c0d302ac31c1689e34571e0 from qemu
This commit is contained in:
Joseph Myers 2020-06-15 13:07:04 -04:00 committed by Lioncash
parent 95368d250b
commit 5a01ea31eb
1 changed files with 49 additions and 5 deletions
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54
qemu/target/i386/fpu_helper.c
View file

@ -55,8 +55,13 @@
#define FPUC_EM 0x3f
#define floatx80_lg2 make_floatx80(0x3ffd, 0x9a209a84fbcff799LL)
#define floatx80_lg2_d make_floatx80(0x3ffd, 0x9a209a84fbcff798LL)
#define floatx80_l2e make_floatx80(0x3fff, 0xb8aa3b295c17f0bcLL)
#define floatx80_l2e_d make_floatx80(0x3fff, 0xb8aa3b295c17f0bbLL)
#define floatx80_l2t make_floatx80(0x4000, 0xd49a784bcd1b8afeLL)
#define floatx80_l2t_u make_floatx80(0x4000, 0xd49a784bcd1b8affLL)
#define floatx80_ln2_d make_floatx80(0x3ffe, 0xb17217f7d1cf79abLL)
#define floatx80_pi_d make_floatx80(0x4000, 0xc90fdaa22168c234LL)
static inline void fpush(CPUX86State *env)
{
@ -510,27 +515,66 @@ void helper_fld1_ST0(CPUX86State *env)
void helper_fldl2t_ST0(CPUX86State *env)
{
ST0 = floatx80_l2t;
switch (env->fpuc & FPU_RC_MASK) {
case FPU_RC_UP:
ST0 = floatx80_l2t_u;
break;
default:
ST0 = floatx80_l2t;
break;
}
}
void helper_fldl2e_ST0(CPUX86State *env)
{
ST0 = floatx80_l2e;
switch (env->fpuc & FPU_RC_MASK) {
case FPU_RC_DOWN:
case FPU_RC_CHOP:
ST0 = floatx80_l2e_d;
break;
default:
ST0 = floatx80_l2e;
break;
}
}
void helper_fldpi_ST0(CPUX86State *env)
{
ST0 = floatx80_pi;
switch (env->fpuc & FPU_RC_MASK) {
case FPU_RC_DOWN:
case FPU_RC_CHOP:
ST0 = floatx80_pi_d;
break;
default:
ST0 = floatx80_pi;
break;
}
}
void helper_fldlg2_ST0(CPUX86State *env)
{
ST0 = floatx80_lg2;
switch (env->fpuc & FPU_RC_MASK) {
case FPU_RC_DOWN:
case FPU_RC_CHOP:
ST0 = floatx80_lg2_d;
break;
default:
ST0 = floatx80_lg2;
break;
}
}
void helper_fldln2_ST0(CPUX86State *env)
{
ST0 = floatx80_ln2;
switch (env->fpuc & FPU_RC_MASK) {
case FPU_RC_DOWN:
case FPU_RC_CHOP:
ST0 = floatx80_ln2_d;
break;
default:
ST0 = floatx80_ln2;
break;
}
}
void helper_fldz_ST0(CPUX86State *env)