On 12/14/2009 04:31 PM, Richard Henderson wrote:
On 12/14/2009 12:11 PM, Laurent Desnogues wrote:
I'll take a closer look at your patch tomorrow.
For the record, I believe this finishes what I had in mind for the
exception handling there in op_handler.c.
Hmph. One more patch for correctness. With this 183.equake runs
correctly. I couldn't remember all the hoops to get runspec.pl to work,
to do the whole testsuite, but I did run this one by hand.
./quake-amd64: Done. Terminating the simulation.
real 0m34.943s
user 0m34.913s
sys 0m0.024s
./quake-axp: Done. Terminating the simulation.
real 33m24.105s
user 33m23.674s
sys 0m0.116s
with identical output.
r~
commit daf11ad5cd50c56d44e36e4ea334c660f8fe4c16
Author: Richard Henderson <r...@twiddle.net>
Date: Mon Dec 14 19:46:57 2009 -0800
target-alpha: Don't ever saturate cvttq.
The previous patch tried allowing saturation if /S;
that doesn't match what the kernels generate.
diff --git a/target-alpha/op_helper.c b/target-alpha/op_helper.c
index d031f56..2d1c3d5 100644
--- a/target-alpha/op_helper.c
+++ b/target-alpha/op_helper.c
@@ -1220,120 +1220,106 @@ uint64_t helper_cvtqs (uint64_t a, uint32_t quals)
is used by the compiler to get unsigned conversion for free with
the same instruction. */
-static uint64_t cvttq_noqual_internal(uint64_t a, uint32_t rounding_mode)
+static uint64_t cvttq_internal(uint64_t a)
{
uint64_t frac, ret = 0;
- uint32_t exp, sign;
+ uint32_t exp, sign, exc = 0;
int shift;
sign = (a >> 63);
exp = (uint32_t)(a >> 52) & 0x7ff;
frac = a & 0xfffffffffffffull;
- /* We already handled denormals in remap_ieee_input; infinities and
- nans are defined to return zero as per truncation. */
- if (exp == 0 || exp == 0x7ff)
- return 0;
-
- /* Restore implicit bit. */
- frac |= 0x10000000000000ull;
-
- /* Note that neither overflow exceptions nor inexact exceptions
- are desired. This lets us streamline the checks quite a bit. */
- shift = exp - 1023 - 52;
- if (shift >= 0) {
- /* In this case the number is so large that we must shift
- the fraction left. There is no rounding to do. */
- if (shift < 63) {
- ret = frac << shift;
- }
+ if (exp == 0) {
+ if (unlikely(frac != 0))
+ goto do_underflow;
+ } else if (exp == 0x7ff) {
+ if (frac == 0)
+ exc = float_flag_overflow;
+ else
+ exc = float_flag_invalid;
} else {
- uint64_t round;
-
- /* In this case the number is smaller than the fraction as
- represented by the 52 bit number. Here we must think
- about rounding the result. Handle this by shifting the
- fractional part of the number into the high bits of ROUND.
- This will let us efficiently handle round-to-nearest. */
- shift = -shift;
- if (shift < 63) {
- ret = frac >> shift;
- round = frac << (64 - shift);
+ /* Restore implicit bit. */
+ frac |= 0x10000000000000ull;
+
+ /* Note that neither overflow exceptions nor inexact exceptions
+ are desired. This lets us streamline the checks quite a bit. */
+ shift = exp - 1023 - 52;
+ if (shift >= 0) {
+ /* In this case the number is so large that we must shift
+ the fraction left. There is no rounding to do. */
+ if (shift < 63) {
+ ret = frac << shift;
+ if ((ret >> shift) != frac)
+ exc = float_flag_overflow;
+ }
} else {
- /* The exponent is so small we shift out everything.
- Leave a sticky bit for proper rounding below. */
- round = 1;
- }
+ uint64_t round;
+
+ /* In this case the number is smaller than the fraction as
+ represented by the 52 bit number. Here we must think
+ about rounding the result. Handle this by shifting the
+ fractional part of the number into the high bits of ROUND.
+ This will let us efficiently handle round-to-nearest. */
+ shift = -shift;
+ if (shift < 63) {
+ ret = frac >> shift;
+ round = frac << (64 - shift);
+ } else {
+ /* The exponent is so small we shift out everything.
+ Leave a sticky bit for proper rounding below. */
+ do_underflow:
+ round = 1;
+ }
- if (round) {
- switch (rounding_mode) {
- case float_round_nearest_even:
- if (round == (1ull << 63)) {
- /* Remaining fraction is exactly 0.5; round to even. */
- ret += (ret & 1);
- } else if (round > (1ull << 63)) {
- ret += 1;
+ if (round) {
+ exc = float_flag_inexact;
+ switch (FP_STATUS.float_rounding_mode) {
+ case float_round_nearest_even:
+ if (round == (1ull << 63)) {
+ /* Fraction is exactly 0.5; round to even. */
+ ret += (ret & 1);
+ } else if (round > (1ull << 63)) {
+ ret += 1;
+ }
+ break;
+ case float_round_to_zero:
+ break;
+ case float_round_up:
+ if (!sign)
+ ret += 1;
+ break;
+ case float_round_down:
+ if (sign)
+ ret += 1;
+ break;
}
- break;
- case float_round_to_zero:
- break;
- case float_round_up:
- if (!sign)
- ret += 1;
- break;
- case float_round_down:
- if (sign)
- ret += 1;
- break;
}
}
+ if (sign)
+ ret = -ret;
}
+ if (unlikely(exc))
+ float_raise(exc, &FP_STATUS);
- if (sign)
- ret = -ret;
return ret;
}
uint64_t helper_cvttq (uint64_t a, uint32_t quals)
{
uint64_t ret;
+ uint32_t token;
- a = remap_ieee_input(quals, a);
-
- if (quals & QUAL_V) {
- float64 fa = t_to_float64(a);
- uint32_t token;
-
- token = begin_fp_exception();
- if ((quals & QUAL_RM_MASK) == QUAL_RM_C) {
- ret = float64_to_int64_round_to_zero(fa, &FP_STATUS);
- } else {
- token |= begin_fp_roundmode(quals);
- ret = float64_to_int64(fa, &FP_STATUS);
- end_fp_roundmode(token);
- }
- end_fp_exception(quals, token);
- } else {
- uint32_t round_mode;
-
- switch (quals & QUAL_RM_MASK) {
- case QUAL_RM_N:
- round_mode = float_round_nearest_even;
- break;
- case QUAL_RM_C:
- default:
- round_mode = float_round_to_zero;
- break;
- case QUAL_RM_M:
- round_mode = float_round_down;
- break;
- case QUAL_RM_D:
- round_mode = FP_STATUS.float_rounding_mode;
- break;
- }
+ /* ??? There's an arugument to be made that when /S is enabled, we
+ should provide the standard IEEE saturated result, instead of
+ the truncated result that we *must* provide when /V is disabled.
+ However, that's not how either the Tru64 or Linux completion
+ handlers actually work, and GCC knows it. */
- ret = cvttq_noqual_internal(a, round_mode);
- }
+ token = begin_fp(quals);
+ a = remap_ieee_input(quals, a);
+ ret = cvttq_internal(a);
+ end_fp(quals, token);
return ret;
}
