tests/tcg/x86_64/fma: add test for exact-denormal output

Add some fma test cases that check for correct handling of FTZ and
for the flag that indicates that the input denormal was consumed.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250519145114.2786534-5-peter.maydell@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/tests/tcg/x86_64/fma.c b/tests/tcg/x86_64/fma.c
index 46f863005ed549f0879dbf5c525e3c07f68605e4..34219614c0ae36b2ed62b926a5b25871c991d4e3 100644 (file)
--- a/tests/tcg/x86_64/fma.c
+++ b/tests/tcg/x86_64/fma.c
@@ -82,6 +82,18 @@ static testdata tests[] = {
      */
     { 0x3fdfffffffffffff, 0x001fffffffffffff, 0x801fffffffffffff, true,
       0x8010000000000000, 0x20 }, /* Enabling FTZ shouldn't change flags */
+    /*
+     * normal * 0 + a denormal. With FTZ disabled this gives an exact
+     * result (equal to the input denormal) that has consumed the denormal.
+     */
+    { 0x3cc8000000000000, 0x0000000000000000, 0x8008000000000000, false,
+      0x8008000000000000, 0x2 }, /* Denormal */
+    /*
+     * With FTZ enabled, this consumes the denormal, returns zero (because
+     * flushed) and indicates also Underflow and Precision.
+     */
+    { 0x3cc8000000000000, 0x0000000000000000, 0x8008000000000000, true,
+      0x8000000000000000, 0x32 }, /* Precision, Underflow, Denormal */
 };
 
 int main(void)