commit 416cfb9f55c84fa3e6df573e891b8098bcaab886
author Nicolas Capens <capn@google.com> Mon Oct 02 17:41:13 2017 -0400
committer Nicolas Capens <nicolascapens@google.com> Tue Oct 03 15:55:32 2017 +0000
tree 42cca96f8f9011a47e3a1b5a6bc0bb59cc69986a
parent 355a5dc1b228bc57a5ffe932b0b9b69d8726b63a

Fix vector packing pseudo-instruction.

When the first source register is different from the destination
register, but equal to the second source, we need to first narrow
the second source to prevent overwriting data we still need. Similar
when the destination is equal to the first source.

Bug b/37496082

Change-Id: I908a8e125a77ec4bf1eb5eab9e48c6112ee4ca13
Reviewed-on: https://chromium-review.googlesource.com/696032
Reviewed-by: Jim Stichnoth <stichnot@chromium.org>
Reviewed-on: https://swiftshader-review.googlesource.com/12949
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>

third_party/subzero/src/IceAssemblerARM32.cpp

diff --git a/third_party/subzero/src/IceAssemblerARM32.cpp b/third_party/subzero/src/IceAssemblerARM32.cpp
index a8e9021..502668c 100644
--- a/third_party/subzero/src/IceAssemblerARM32.cpp
+++ b/third_party/subzero/src/IceAssemblerARM32.cpp
@@ -3731,16 +3731,15 @@
   VqmovnOpcode |= (encodeElmtType(DestElmtTy) << ElmtShift);
 
   if (Qm != Qd) {
-    // Narrow first source operand to lower half of destination.
-    emitSIMDBase(VqmovnOpcode, Dd + 0, 0, Dm, UseQRegs, IsFloatTy);
     // Narrow second source operand to upper half of destination.
     emitSIMDBase(VqmovnOpcode, Dd + 1, 0, Dn, UseQRegs, IsFloatTy);
+    // Narrow first source operand to lower half of destination.
+    emitSIMDBase(VqmovnOpcode, Dd + 0, 0, Dm, UseQRegs, IsFloatTy);
   } else if (Qn != Qd) {
-    // Narrow second source operand to upper half of destination.
-    emitSIMDBase(VqmovnOpcode, Dd + 1, 0, Dn, UseQRegs, IsFloatTy);
     // Narrow first source operand to lower half of destination.
     emitSIMDBase(VqmovnOpcode, Dd + 0, 0, Dm, UseQRegs, IsFloatTy);
-
+    // Narrow second source operand to upper half of destination.
+    emitSIMDBase(VqmovnOpcode, Dd + 1, 0, Dn, UseQRegs, IsFloatTy);
   } else {
     // Narrow first source operand to lower half of destination.
     emitSIMDBase(VqmovnOpcode, Dd, 0, Dm, UseQRegs, IsFloatTy);