target/arm: Honour FPCR.FZ in FRECPX

The FRECPX instructions should (like most other floating point operations)
honour the FPCR.FZ bit which specifies whether input denormals should
be flushed to zero (or FZ16 for the half-precision version).
We forgot to implement this, which doesn't affect the results (since
the calculation doesn't actually care about the mantissa bits) but did
mean we were failing to set the FPSR.IDC bit.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180521172712.19930-1-peter.maydell@linaro.org

diff --git a/target/arm/helper-a64.c b/target/arm/helper-a64.c
index f92bdea732f405faf9401f4abea8fa51277c0db0..c4d2a048278335bf44315150b432ebfab5bec020 100644 (file)
--- a/target/arm/helper-a64.c
+++ b/target/arm/helper-a64.c
@@ -384,6 +384,8 @@ float16 HELPER(frecpx_f16)(float16 a, void *fpstp)
         return nan;
     }
 
+    a = float16_squash_input_denormal(a, fpst);
+
     val16 = float16_val(a);
     sbit = 0x8000 & val16;
     exp = extract32(val16, 10, 5);
@@ -413,6 +415,8 @@ float32 HELPER(frecpx_f32)(float32 a, void *fpstp)
         return nan;
     }
 
+    a = float32_squash_input_denormal(a, fpst);
+
     val32 = float32_val(a);
     sbit = 0x80000000ULL & val32;
     exp = extract32(val32, 23, 8);
@@ -442,6 +446,8 @@ float64 HELPER(frecpx_f64)(float64 a, void *fpstp)
         return nan;
     }
 
+    a = float64_squash_input_denormal(a, fpst);
+
     val64 = float64_val(a);
     sbit = 0x8000000000000000ULL & val64;
     exp = extract64(float64_val(a), 52, 11);