tcg: Fix helper function vs host abi for float16

Depending on the host abi, float16, aka uint16_t, values are
passed and returned either zero-extended in the host register
or with garbage at the top of the host register.

The tcg code generator has so far been assuming garbage, as that
matches the x86 abi, but this is incorrect for other host abis.
Further, target/arm has so far been assuming zero-extended results,
so that it may store the 16-bit value into a 32-bit slot with the
high 16-bits already clear.

Rectify both problems by mapping "f16" in the helper definition
to uint32_t instead of (a typedef for) uint16_t.  This forces
the host compiler to assume garbage in the upper 16 bits on input
and to zero-extend the result on output.

Cc: qemu-stable@nongnu.org
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Message-id: 20180522175629.24932-1-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 18 insertions, 17 deletions

diff --git a/target/arm/helper-a64.c b/target/arm/helper-a64.c
index c4d2a04827..7f6ad3000b 100644
--- a/target/arm/helper-a64.c
+++ b/target/arm/helper-a64.c
@@ -85,12 +85,12 @@ static inline uint32_t float_rel_to_flags(int res)
     return flags;
 }
 
-uint64_t HELPER(vfp_cmph_a64)(float16 x, float16 y, void *fp_status)
+uint64_t HELPER(vfp_cmph_a64)(uint32_t x, uint32_t y, void *fp_status)
 {
     return float_rel_to_flags(float16_compare_quiet(x, y, fp_status));
 }
 
-uint64_t HELPER(vfp_cmpeh_a64)(float16 x, float16 y, void *fp_status)
+uint64_t HELPER(vfp_cmpeh_a64)(uint32_t x, uint32_t y, void *fp_status)
 {
     return float_rel_to_flags(float16_compare(x, y, fp_status));
 }
@@ -214,7 +214,7 @@ uint64_t HELPER(neon_cgt_f64)(float64 a, float64 b, void *fpstp)
 #define float64_three make_float64(0x4008000000000000ULL)
 #define float64_one_point_five make_float64(0x3FF8000000000000ULL)
 
-float16 HELPER(recpsf_f16)(float16 a, float16 b, void *fpstp)
+uint32_t HELPER(recpsf_f16)(uint32_t a, uint32_t b, void *fpstp)
 {
     float_status *fpst = fpstp;
 
@@ -259,7 +259,7 @@ float64 HELPER(recpsf_f64)(float64 a, float64 b, void *fpstp)
     return float64_muladd(a, b, float64_two, 0, fpst);
 }
 
-float16 HELPER(rsqrtsf_f16)(float16 a, float16 b, void *fpstp)
+uint32_t HELPER(rsqrtsf_f16)(uint32_t a, uint32_t b, void *fpstp)
 {
     float_status *fpst = fpstp;
 
@@ -366,7 +366,7 @@ uint64_t HELPER(neon_addlp_u16)(uint64_t a)
 }
 
 /* Floating-point reciprocal exponent - see FPRecpX in ARM ARM */
-float16 HELPER(frecpx_f16)(float16 a, void *fpstp)
+uint32_t HELPER(frecpx_f16)(uint32_t a, void *fpstp)
 {
     float_status *fpst = fpstp;
     uint16_t val16, sbit;
@@ -701,7 +701,7 @@ void HELPER(casp_be_parallel)(CPUARMState *env, uint32_t rs, uint64_t addr,
 #define ADVSIMD_HELPER(name, suffix) HELPER(glue(glue(advsimd_, name), suffix))
 
 #define ADVSIMD_HALFOP(name) \
-float16 ADVSIMD_HELPER(name, h)(float16 a, float16 b, void *fpstp) \
+uint32_t ADVSIMD_HELPER(name, h)(uint32_t a, uint32_t b, void *fpstp) \
 { \
     float_status *fpst = fpstp; \
     return float16_ ## name(a, b, fpst);    \
@@ -761,7 +761,8 @@ ADVSIMD_HALFOP(mulx)
 ADVSIMD_TWOHALFOP(mulx)
 
 /* fused multiply-accumulate */
-float16 HELPER(advsimd_muladdh)(float16 a, float16 b, float16 c, void *fpstp)
+uint32_t HELPER(advsimd_muladdh)(uint32_t a, uint32_t b, uint32_t c,
+                                 void *fpstp)
 {
     float_status *fpst = fpstp;
     return float16_muladd(a, b, c, 0, fpst);
@@ -792,14 +793,14 @@ uint32_t HELPER(advsimd_muladd2h)(uint32_t two_a, uint32_t two_b,
 
 #define ADVSIMD_CMPRES(test) (test) ? 0xffff : 0
 
-uint32_t HELPER(advsimd_ceq_f16)(float16 a, float16 b, void *fpstp)
+uint32_t HELPER(advsimd_ceq_f16)(uint32_t a, uint32_t b, void *fpstp)
 {
     float_status *fpst = fpstp;
     int compare = float16_compare_quiet(a, b, fpst);
     return ADVSIMD_CMPRES(compare == float_relation_equal);
 }
 
-uint32_t HELPER(advsimd_cge_f16)(float16 a, float16 b, void *fpstp)
+uint32_t HELPER(advsimd_cge_f16)(uint32_t a, uint32_t b, void *fpstp)
 {
     float_status *fpst = fpstp;
     int compare = float16_compare(a, b, fpst);
@@ -807,14 +808,14 @@ uint32_t HELPER(advsimd_cge_f16)(float16 a, float16 b, void *fpstp)
                           compare == float_relation_equal);
 }
 
-uint32_t HELPER(advsimd_cgt_f16)(float16 a, float16 b, void *fpstp)
+uint32_t HELPER(advsimd_cgt_f16)(uint32_t a, uint32_t b, void *fpstp)
 {
     float_status *fpst = fpstp;
     int compare = float16_compare(a, b, fpst);
     return ADVSIMD_CMPRES(compare == float_relation_greater);
 }
 
-uint32_t HELPER(advsimd_acge_f16)(float16 a, float16 b, void *fpstp)
+uint32_t HELPER(advsimd_acge_f16)(uint32_t a, uint32_t b, void *fpstp)
 {
     float_status *fpst = fpstp;
     float16 f0 = float16_abs(a);
@@ -824,7 +825,7 @@ uint32_t HELPER(advsimd_acge_f16)(float16 a, float16 b, void *fpstp)
                           compare == float_relation_equal);
 }
 
-uint32_t HELPER(advsimd_acgt_f16)(float16 a, float16 b, void *fpstp)
+uint32_t HELPER(advsimd_acgt_f16)(uint32_t a, uint32_t b, void *fpstp)
 {
     float_status *fpst = fpstp;
     float16 f0 = float16_abs(a);
@@ -834,12 +835,12 @@ uint32_t HELPER(advsimd_acgt_f16)(float16 a, float16 b, void *fpstp)
 }
 
 /* round to integral */
-float16 HELPER(advsimd_rinth_exact)(float16 x, void *fp_status)
+uint32_t HELPER(advsimd_rinth_exact)(uint32_t x, void *fp_status)
 {
     return float16_round_to_int(x, fp_status);
 }
 
-float16 HELPER(advsimd_rinth)(float16 x, void *fp_status)
+uint32_t HELPER(advsimd_rinth)(uint32_t x, void *fp_status)
 {
     int old_flags = get_float_exception_flags(fp_status), new_flags;
     float16 ret;
@@ -863,7 +864,7 @@ float16 HELPER(advsimd_rinth)(float16 x, void *fp_status)
  * setting the mode appropriately before calling the helper.
  */
 
-uint32_t HELPER(advsimd_f16tosinth)(float16 a, void *fpstp)
+uint32_t HELPER(advsimd_f16tosinth)(uint32_t a, void *fpstp)
 {
     float_status *fpst = fpstp;
 
@@ -875,7 +876,7 @@ uint32_t HELPER(advsimd_f16tosinth)(float16 a, void *fpstp)
     return float16_to_int16(a, fpst);
 }
 
-uint32_t HELPER(advsimd_f16touinth)(float16 a, void *fpstp)
+uint32_t HELPER(advsimd_f16touinth)(uint32_t a, void *fpstp)
 {
     float_status *fpst = fpstp;
 
@@ -891,7 +892,7 @@ uint32_t HELPER(advsimd_f16touinth)(float16 a, void *fpstp)
  * Square Root and Reciprocal square root
  */
 
-float16 HELPER(sqrt_f16)(float16 a, void *fpstp)
+uint32_t HELPER(sqrt_f16)(uint32_t a, void *fpstp)
 {
     float_status *s = fpstp;