PPC: [was-simd] Fix Vector pack behaviour.

Due to the lane numbering difference between Intel and IBM machines,
we need to switch the input registers when doing a vector pack.

Change-Id: Id01d6292cb2a65b78dccdf3bab1d5ff010e1d018
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2569996Reviewed-by: Junliang Yan <junyan@redhat.com>
Reviewed-by: Milad Fa <mfarazma@redhat.com>
Commit-Queue: Milad Fa <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/master@{#71575}

src/compiler/backend/ppc/code-generator-ppc.cc

@@ -3164,23 +3164,23 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       break;
     }
     case kPPC_I16x8SConvertI32x4: {
-      __ vpkswss(i.OutputSimd128Register(), i.InputSimd128Register(0),
-                 i.InputSimd128Register(1));
+      __ vpkswss(i.OutputSimd128Register(), i.InputSimd128Register(1),
+                 i.InputSimd128Register(0));
       break;
     }
     case kPPC_I16x8UConvertI32x4: {
-      __ vpkswus(i.OutputSimd128Register(), i.InputSimd128Register(0),
-                 i.InputSimd128Register(1));
+      __ vpkswus(i.OutputSimd128Register(), i.InputSimd128Register(1),
+                 i.InputSimd128Register(0));
       break;
     }
     case kPPC_I8x16SConvertI16x8: {
-      __ vpkshss(i.OutputSimd128Register(), i.InputSimd128Register(0),
-                 i.InputSimd128Register(1));
+      __ vpkshss(i.OutputSimd128Register(), i.InputSimd128Register(1),
+                 i.InputSimd128Register(0));
       break;
     }
     case kPPC_I8x16UConvertI16x8: {
-      __ vpkshus(i.OutputSimd128Register(), i.InputSimd128Register(0),
-                 i.InputSimd128Register(1));
+      __ vpkshus(i.OutputSimd128Register(), i.InputSimd128Register(1),
+                 i.InputSimd128Register(0));
       break;
     }
     case kPPC_I8x16Shuffle: {