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[PULL,10/29] softfloat: Reduce FloatFmt

Message ID 20210603214131.629841-11-richard.henderson@linaro.org
State New
Headers show
Series softfloat patch queue | expand

Commit Message

Richard Henderson June 3, 2021, 9:41 p.m. UTC 
Remove frac_lsb, frac_lsbm1, roundeven_mask.  Compute
these from round_mask in parts$N_uncanon_normal.

With floatx80, round_mask will not be tied to frac_shift.
Everything else is easily computable.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

---
 fpu/softfloat.c           | 29 ++++++++++++-----------------
 fpu/softfloat-parts.c.inc |  6 +++---
 2 files changed, 15 insertions(+), 20 deletions(-)

-- 
2.25.1
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Patch

diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index ea7ee13201..741480c568 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -563,9 +563,7 @@  typedef struct {
  *   frac_size: the size of the fraction field
  *   frac_shift: shift to normalise the fraction with DECOMPOSED_BINARY_POINT
  * The following are computed based the size of fraction
- *   frac_lsb: least significant bit of fraction
- *   frac_lsbm1: the bit below the least significant bit (for rounding)
- *   round_mask/roundeven_mask: masks used for rounding
+ *   round_mask: bits below lsb which must be rounded
  * The following optional modifiers are available:
  *   arm_althp: handle ARM Alternative Half Precision
  */
@@ -575,24 +573,21 @@  typedef struct {
     int exp_max;
     int frac_size;
     int frac_shift;
-    uint64_t frac_lsb;
-    uint64_t frac_lsbm1;
-    uint64_t round_mask;
-    uint64_t roundeven_mask;
     bool arm_althp;
+    uint64_t round_mask;
 } FloatFmt;
 
 /* Expand fields based on the size of exponent and fraction */
-#define FLOAT_PARAMS(E, F)                                           \
-    .exp_size       = E,                                             \
-    .exp_bias       = ((1 << E) - 1) >> 1,                           \
-    .exp_max        = (1 << E) - 1,                                  \
-    .frac_size      = F,                                             \
-    .frac_shift     = (-F - 1) & 63,                                 \
-    .frac_lsb       = 1ull << ((-F - 1) & 63),                       \
-    .frac_lsbm1     = 1ull << ((-F - 2) & 63),                       \
-    .round_mask     = (1ull << ((-F - 1) & 63)) - 1,                 \
-    .roundeven_mask = (2ull << ((-F - 1) & 63)) - 1
+#define FLOAT_PARAMS_(E, F)                             \
+    .exp_size       = E,                                \
+    .exp_bias       = ((1 << E) - 1) >> 1,              \
+    .exp_max        = (1 << E) - 1,                     \
+    .frac_size      = F
+
+#define FLOAT_PARAMS(E, F)                              \
+    FLOAT_PARAMS_(E, F),                                \
+    .frac_shift     = (-F - 1) & 63,                    \
+    .round_mask     = (1ull << ((-F - 1) & 63)) - 1
 
 static const FloatFmt float16_params = {
     FLOAT_PARAMS(5, 10)
diff --git a/fpu/softfloat-parts.c.inc b/fpu/softfloat-parts.c.inc
index e05909db8c..a026581c33 100644
--- a/fpu/softfloat-parts.c.inc
+++ b/fpu/softfloat-parts.c.inc
@@ -145,10 +145,10 @@  static void partsN(uncanon_normal)(FloatPartsN *p, float_status *s,
 {
     const int exp_max = fmt->exp_max;
     const int frac_shift = fmt->frac_shift;
-    const uint64_t frac_lsb = fmt->frac_lsb;
-    const uint64_t frac_lsbm1 = fmt->frac_lsbm1;
     const uint64_t round_mask = fmt->round_mask;
-    const uint64_t roundeven_mask = fmt->roundeven_mask;
+    const uint64_t frac_lsb = round_mask + 1;
+    const uint64_t frac_lsbm1 = round_mask ^ (round_mask >> 1);
+    const uint64_t roundeven_mask = round_mask | frac_lsb;
     uint64_t inc;
     bool overflow_norm = false;
     int exp, flags = 0;