[AArch64] Prefer "mov" over "orr" to materialize constants.

This is generally more readable due to the way the assembler aliases
work.

(This causes a lot of test changes, but it's not really as scary as it
looks at first glance; it's just mechanically changing a bunch of checks
for orr to check for mov instead.)

Differential Revision: https://reviews.llvm.org/D59720

llvm-svn: 356954

1 files changed, 5 insertions, 2 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64ExpandImm.cpp b/llvm/lib/Target/AArch64/AArch64ExpandImm.cpp
index c8602dabcd5..c764af80eb8 100644
--- a/llvm/lib/Target/AArch64/AArch64ExpandImm.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ExpandImm.cpp
@@ -318,8 +318,11 @@ void expandMOVImm(uint64_t Imm, unsigned BitSize,
       ZeroChunks++;
   }
 
-  // FIXME: Prefer MOVZ/MOVN over ORR because of the rules for the "mov"
-  // alias.
+  // Prefer MOVZ/MOVN over ORR because of the rules for the "mov" alias.
+  if ((BitSize / 16) - OneChunks <= 1 || (BitSize / 16) - ZeroChunks <= 1) {
+    expandMOVImmSimple(Imm, BitSize, OneChunks, ZeroChunks, Insn);
+    return;
+  }
 
   // Try a single ORR.
   uint64_t UImm = Imm << (64 - BitSize) >> (64 - BitSize);