[RFC PATCH 2/8] softfloat: Use int128.h for some operations

[Alex Bennée]

From: Richard Henderson <richard.henderson@linaro.org>

Use our Int128, which wraps the compiler's __int128_t,
instead of open-coding left shifts and arithmetic.
We'd need to extend Int128 to have unsigned operations
to replace more than these three.

Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20200925152047.709901-3-richard.henderson@linaro.org>
---
 include/fpu/softfloat-macros.h | 39 +++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 19 deletions(-)

diff --git a/include/fpu/softfloat-macros.h b/include/fpu/softfloat-macros.h
index 57845f8af0..95d88d05b8 100644
--- a/include/fpu/softfloat-macros.h
+++ b/include/fpu/softfloat-macros.h
@@ -84,6 +84,7 @@ this code that are retained.
 
 #include "fpu/softfloat-types.h"
 #include "qemu/host-utils.h"
+#include "qemu/int128.h"
 
 /*----------------------------------------------------------------------------
 | Shifts `a' right by the number of bits given in `count'.  If any nonzero
@@ -352,13 +353,11 @@ static inline void shortShift128Left(uint64_t a0, 
uint64_t a1, int count,
 static inline void shift128Left(uint64_t a0, uint64_t a1, int count,
                                 uint64_t *z0Ptr, uint64_t *z1Ptr)
 {
-    if (count < 64) {
-        *z1Ptr = a1 << count;
-        *z0Ptr = count == 0 ? a0 : (a0 << count) | (a1 >> (-count & 63));
-    } else {
-        *z1Ptr = 0;
-        *z0Ptr = a1 << (count - 64);
-    }
+    Int128 a = int128_make128(a1, a0);
+    Int128 z = int128_lshift(a, count);
+
+    *z0Ptr = int128_gethi(z);
+    *z1Ptr = int128_getlo(z);
 }
 
 /*----------------------------------------------------------------------------
@@ -405,15 +404,15 @@ static inline void
 *----------------------------------------------------------------------------*/
 
 static inline void
- add128(
-     uint64_t a0, uint64_t a1, uint64_t b0, uint64_t b1, uint64_t *z0Ptr, 
uint64_t *z1Ptr )
+add128(uint64_t a0, uint64_t a1, uint64_t b0, uint64_t b1,
+       uint64_t *z0Ptr, uint64_t *z1Ptr)
 {
-    uint64_t z1;
-
-    z1 = a1 + b1;
-    *z1Ptr = z1;
-    *z0Ptr = a0 + b0 + ( z1 < a1 );
+    Int128 a = int128_make128(a1, a0);
+    Int128 b = int128_make128(b1, b0);
+    Int128 z = int128_add(a, b);
 
+    *z0Ptr = int128_gethi(z);
+    *z1Ptr = int128_getlo(z);
 }
 
 /*----------------------------------------------------------------------------
@@ -463,13 +462,15 @@ static inline void
 *----------------------------------------------------------------------------*/
 
 static inline void
- sub128(
-     uint64_t a0, uint64_t a1, uint64_t b0, uint64_t b1, uint64_t *z0Ptr, 
uint64_t *z1Ptr )
+sub128(uint64_t a0, uint64_t a1, uint64_t b0, uint64_t b1,
+       uint64_t *z0Ptr, uint64_t *z1Ptr)
 {
+    Int128 a = int128_make128(a1, a0);
+    Int128 b = int128_make128(b1, b0);
+    Int128 z = int128_sub(a, b);
 
-    *z1Ptr = a1 - b1;
-    *z0Ptr = a0 - b0 - ( a1 < b1 );
-
+    *z0Ptr = int128_gethi(z);
+    *z1Ptr = int128_getlo(z);
 }
 
 /*----------------------------------------------------------------------------
-- 
2.20.1