[PULL 053/115] target/i386: fix fscale handling of invalid exponent encodings

[Paolo Bonzini]

From: Joseph Myers <joseph@codesourcery.com>

The fscale implementation does not check for invalid encodings in the
exponent operand, thus treating them like INT_MIN (the value returned
for invalid encodings by floatx80_to_int32_round_to_zero).  Fix it to
treat them similarly to signaling NaN exponents, thus generating a
quiet NaN result.

Signed-off-by: Joseph Myers <joseph@codesourcery.com>
Message-Id: <alpine.DEB.2.21.2005070044190.18350@digraph.polyomino.org.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 target/i386/fpu_helper.c          |  5 ++++-
 tests/tcg/i386/test-i386-fscale.c | 29 +++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/target/i386/fpu_helper.c b/target/i386/fpu_helper.c
index 0671de6952..10ff90370e 100644
--- a/target/i386/fpu_helper.c
+++ b/target/i386/fpu_helper.c
@@ -968,7 +968,10 @@ void helper_frndint(CPUX86State *env)
 
 void helper_fscale(CPUX86State *env)
 {
-    if (floatx80_is_any_nan(ST1)) {
+    if (floatx80_invalid_encoding(ST1)) {
+        float_raise(float_flag_invalid, &env->fp_status);
+        ST0 = floatx80_default_nan(&env->fp_status);
+    } else if (floatx80_is_any_nan(ST1)) {
         ST0 = ST1;
         if (floatx80_is_signaling_nan(ST0, &env->fp_status)) {
             float_raise(float_flag_invalid, &env->fp_status);
diff --git a/tests/tcg/i386/test-i386-fscale.c 
b/tests/tcg/i386/test-i386-fscale.c
index aecac5125f..b65a055d0a 100644
--- a/tests/tcg/i386/test-i386-fscale.c
+++ b/tests/tcg/i386/test-i386-fscale.c
@@ -8,6 +8,11 @@ union u {
     long double ld;
 };
 
+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_res;
 
 int isnan_ld(long double x)
@@ -33,5 +38,29 @@ int main(void)
         printf("FAIL: fscale snan\n");
         ret = 1;
     }
+    __asm__ volatile ("fscale" : "=t" (ld_res) :
+                      "0" (2.5L), "u" (ld_invalid_1.ld));
+    if (!isnan_ld(ld_res) || issignaling_ld(ld_res)) {
+        printf("FAIL: fscale invalid 1\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fscale" : "=t" (ld_res) :
+                      "0" (2.5L), "u" (ld_invalid_2.ld));
+    if (!isnan_ld(ld_res) || issignaling_ld(ld_res)) {
+        printf("FAIL: fscale invalid 2\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fscale" : "=t" (ld_res) :
+                      "0" (2.5L), "u" (ld_invalid_3.ld));
+    if (!isnan_ld(ld_res) || issignaling_ld(ld_res)) {
+        printf("FAIL: fscale invalid 3\n");
+        ret = 1;
+    }
+    __asm__ volatile ("fscale" : "=t" (ld_res) :
+                      "0" (2.5L), "u" (ld_invalid_4.ld));
+    if (!isnan_ld(ld_res) || issignaling_ld(ld_res)) {
+        printf("FAIL: fscale invalid 4\n");
+        ret = 1;
+    }
     return ret;
 }
-- 
2.26.2