[PPC64LE] Implement little-endian semantics for vec_sums
The PowerPC vsumsws instruction, accessed via vec_sums, is defined
architecturally with a big-endian bias, in that the second input vector
and the result always reference big-endian element 3 (little-endian
element 0). For ease of porting, the programmer wants elements 3 in
both cases.
To provide this semantics, for little endian we generate a permute for
the second input vector prior to the vsumsws instruction, and generate
a permute for the result vector following the vsumsws instruction.
The correctness of this code is tested by the new sums.c test added in
a previous patch, as well as the modifications to
builtins-ppc-altivec.c in the present patch.
llvm-svn: 210449
diff --git a/clang/lib/Headers/altivec.h b/clang/lib/Headers/altivec.h
index 65990e0..bda5a0e 100644
--- a/clang/lib/Headers/altivec.h
+++ b/clang/lib/Headers/altivec.h
@@ -8398,10 +8398,26 @@
/* vec_sums */
+/* The vsumsws instruction has a big-endian bias, so that the second
+ input vector and the result always reference big-endian element 3
+ (little-endian element 0). For ease of porting the programmer
+ wants element 3 in both cases, so for little endian we must perform
+ some permutes. */
+
static vector signed int __attribute__((__always_inline__))
vec_sums(vector signed int __a, vector signed int __b)
{
+#ifdef __LITTLE_ENDIAN__
+ __b = (vector signed int)
+ vec_perm(__b, __b, (vector unsigned char)
+ (12,13,14,15,0,1,2,3,4,5,6,7,8,9,10,11));
+ __b = __builtin_altivec_vsumsws(__a, __b);
+ return (vector signed int)
+ vec_perm(__b, __b, (vector unsigned char)
+ (4,5,6,7,8,9,10,11,12,13,14,15,0,1,2,3));
+#else
return __builtin_altivec_vsumsws(__a, __b);
+#endif
}
/* vec_vsumsws */
@@ -8409,7 +8425,17 @@
static vector signed int __attribute__((__always_inline__))
vec_vsumsws(vector signed int __a, vector signed int __b)
{
+#ifdef __LITTLE_ENDIAN__
+ __b = (vector signed int)
+ vec_perm(__b, __b, (vector unsigned char)
+ (12,13,14,15,0,1,2,3,4,5,6,7,8,9,10,11));
+ __b = __builtin_altivec_vsumsws(__a, __b);
+ return (vector signed int)
+ vec_perm(__b, __b, (vector unsigned char)
+ (4,5,6,7,8,9,10,11,12,13,14,15,0,1,2,3));
+#else
return __builtin_altivec_vsumsws(__a, __b);
+#endif
}
/* vec_trunc */