diff mbox series

[1/5] target/i386: implement special cases for fxtract

Message ID alpine.DEB.2.21.2005070042360.18350@digraph.polyomino.org.uk
State New
Headers show
Series [1/5] target/i386: implement special cases for fxtract | expand

Commit Message

Joseph Myers May 7, 2020, 12:43 a.m. UTC 
The implementation of the fxtract instruction treats all nonzero
operands as normal numbers, so yielding incorrect results for invalid
formats, infinities, NaNs and subnormal and pseudo-denormal operands.
Implement appropriate handling of all those cases.

Signed-off-by: Joseph Myers <joseph@codesourcery.com>
---
 target/i386/fpu_helper.c           |  25 +++++-
 tests/tcg/i386/test-i386-fxtract.c | 120 +++++++++++++++++++++++++++++
 2 files changed, 144 insertions(+), 1 deletion(-)
 create mode 100644 tests/tcg/i386/test-i386-fxtract.c
diff mbox series

Patch

diff --git a/target/i386/fpu_helper.c b/target/i386/fpu_helper.c
index 792a128a6d..71a696a863 100644
--- a/target/i386/fpu_helper.c
+++ b/target/i386/fpu_helper.c
@@ -767,10 +767,33 @@  void helper_fxtract(CPUX86State *env)
                            &env->fp_status);
         fpush(env);
         ST0 = temp.d;
+    } else if (floatx80_invalid_encoding(ST0)) {
+        float_raise(float_flag_invalid, &env->fp_status);
+        ST0 = floatx80_default_nan(&env->fp_status);
+        fpush(env);
+        ST0 = ST1;
+    } else if (floatx80_is_any_nan(ST0)) {
+        if (floatx80_is_signaling_nan(ST0, &env->fp_status)) {
+            float_raise(float_flag_invalid, &env->fp_status);
+            ST0 = floatx80_silence_nan(ST0, &env->fp_status);
+        }
+        fpush(env);
+        ST0 = ST1;
+    } else if (floatx80_is_infinity(ST0)) {
+        fpush(env);
+        ST0 = ST1;
+        ST1 = floatx80_infinity;
     } else {
         int expdif;
 
-        expdif = EXPD(temp) - EXPBIAS;
+        if (EXPD(temp) == 0) {
+            int shift = clz64(temp.l.lower);
+            temp.l.lower <<= shift;
+            expdif = 1 - EXPBIAS - shift;
+            float_raise(float_flag_input_denormal, &env->fp_status);
+        } else {
+            expdif = EXPD(temp) - EXPBIAS;
+        }
         /* DP exponent bias */
         ST0 = int32_to_floatx80(expdif, &env->fp_status);
         fpush(env);
diff --git a/tests/tcg/i386/test-i386-fxtract.c b/tests/tcg/i386/test-i386-fxtract.c
new file mode 100644
index 0000000000..64fd93d333
--- /dev/null
+++ b/tests/tcg/i386/test-i386-fxtract.c
@@ -0,0 +1,120 @@ 
+/* Test fxtract instruction.  */
+
+#include <stdint.h>
+#include <stdio.h>
+
+union u {
+    struct { uint64_t sig; uint16_t sign_exp; } s;
+    long double ld;
+};
+
+volatile union u ld_pseudo_m16382 = { .s = { UINT64_C(1) << 63, 0 } };
+volatile union u ld_invalid_1 = { .s = { 1, 1234 } };
+volatile union u ld_invalid_2 = { .s = { 0, 1234 } };
+volatile union u ld_invalid_3 = { .s = { 0, 0x7fff } };
+volatile union u ld_invalid_4 = { .s = { (UINT64_C(1) << 63) - 1, 0x7fff } };
+
+volatile long double ld_sig, ld_exp;
+
+int isnan_ld(long double x)
+{
+  union u tmp = { .ld = x };
+  return ((tmp.s.sign_exp & 0x7fff) == 0x7fff &&
+          (tmp.s.sig >> 63) != 0 &&
+          (tmp.s.sig << 1) != 0);
+}
+
+int issignaling_ld(long double x)
+{
+    union u tmp = { .ld = x };
+    return isnan_ld(x) && (tmp.s.sig & UINT64_C(0x4000000000000000)) == 0;
+}
+
+int main(void)
+{
+    int ret = 0;
+    __asm__ volatile ("fxtract" : "=t" (ld_sig), "=u" (ld_exp) : "0" (2.5L));
+    if (ld_sig != 1.25L || ld_exp != 1.0L) {
+        printf("FAIL: fxtract 2.5\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fxtract" : "=t" (ld_sig), "=u" (ld_exp) : "0" (0.0L));
+    if (ld_sig != 0.0L || __builtin_copysignl(1.0L, ld_sig) != 1.0L ||
+        ld_exp != -__builtin_infl()) {
+        printf("FAIL: fxtract 0.0\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fxtract" : "=t" (ld_sig), "=u" (ld_exp) : "0" (-0.0L));
+    if (ld_sig != -0.0L || __builtin_copysignl(1.0L, ld_sig) != -1.0L ||
+        ld_exp != -__builtin_infl()) {
+        printf("FAIL: fxtract -0.0\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fxtract" : "=t" (ld_sig), "=u" (ld_exp) :
+                      "0" (__builtin_infl()));
+    if (ld_sig != __builtin_infl() || ld_exp != __builtin_infl()) {
+        printf("FAIL: fxtract inf\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fxtract" : "=t" (ld_sig), "=u" (ld_exp) :
+                      "0" (-__builtin_infl()));
+    if (ld_sig != -__builtin_infl() || ld_exp != __builtin_infl()) {
+        printf("FAIL: fxtract -inf\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fxtract" : "=t" (ld_sig), "=u" (ld_exp) :
+                      "0" (__builtin_nanl("")));
+    if (!isnan_ld(ld_sig) || issignaling_ld(ld_sig) ||
+        !isnan_ld(ld_exp) || issignaling_ld(ld_exp)) {
+        printf("FAIL: fxtract qnan\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fxtract" : "=t" (ld_sig), "=u" (ld_exp) :
+                      "0" (__builtin_nansl("")));
+    if (!isnan_ld(ld_sig) || issignaling_ld(ld_sig) ||
+        !isnan_ld(ld_exp) || issignaling_ld(ld_exp)) {
+        printf("FAIL: fxtract snan\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fxtract" : "=t" (ld_sig), "=u" (ld_exp) :
+                      "0" (0x1p-16445L));
+    if (ld_sig != 1.0L || ld_exp != -16445.0L) {
+        printf("FAIL: fxtract subnormal\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fxtract" : "=t" (ld_sig), "=u" (ld_exp) :
+                      "0" (ld_pseudo_m16382.ld));
+    if (ld_sig != 1.0L || ld_exp != -16382.0L) {
+        printf("FAIL: fxtract pseudo\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fxtract" : "=t" (ld_sig), "=u" (ld_exp) :
+                      "0" (ld_invalid_1.ld));
+    if (!isnan_ld(ld_sig) || issignaling_ld(ld_sig) ||
+        !isnan_ld(ld_exp) || issignaling_ld(ld_exp)) {
+        printf("FAIL: fxtract invalid 1\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fxtract" : "=t" (ld_sig), "=u" (ld_exp) :
+                      "0" (ld_invalid_2.ld));
+    if (!isnan_ld(ld_sig) || issignaling_ld(ld_sig) ||
+        !isnan_ld(ld_exp) || issignaling_ld(ld_exp)) {
+        printf("FAIL: fxtract invalid 2\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fxtract" : "=t" (ld_sig), "=u" (ld_exp) :
+                      "0" (ld_invalid_3.ld));
+    if (!isnan_ld(ld_sig) || issignaling_ld(ld_sig) ||
+        !isnan_ld(ld_exp) || issignaling_ld(ld_exp)) {
+        printf("FAIL: fxtract invalid 3\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fxtract" : "=t" (ld_sig), "=u" (ld_exp) :
+                      "0" (ld_invalid_4.ld));
+    if (!isnan_ld(ld_sig) || issignaling_ld(ld_sig) ||
+        !isnan_ld(ld_exp) || issignaling_ld(ld_exp)) {
+        printf("FAIL: fxtract invalid 4\n");
+        ret = 1;
+    }
+    return ret;
+}