[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

1 files changed, 4 insertions, 0 deletions

diff --git a/clang/test/CodeGen/builtins-ppc-altivec.c b/clang/test/CodeGen/builtins-ppc-altivec.c
index 8277f5dda7d..c94656e6b5e 100644
--- a/clang/test/CodeGen/builtins-ppc-altivec.c
+++ b/clang/test/CodeGen/builtins-ppc-altivec.c
@@ -5155,11 +5155,15 @@ void test6() {
   /* vec_sums */
   res_vi = vec_sums(vi, vi);
 // CHECK: @llvm.ppc.altivec.vsumsws
+// CHECK-LE: @llvm.ppc.altivec.vperm
 // CHECK-LE: @llvm.ppc.altivec.vsumsws
+// CHECK-LE: @llvm.ppc.altivec.vperm
 
   res_vi = vec_vsumsws(vi, vi);
 // CHECK: @llvm.ppc.altivec.vsumsws
+// CHECK-LE: @llvm.ppc.altivec.vperm
 // CHECK-LE: @llvm.ppc.altivec.vsumsws
+// CHECK-LE: @llvm.ppc.altivec.vperm
 
   /* vec_trunc */
   res_vf = vec_trunc(vf);