From 6e988c5976635aaacdf4a717b9489eb208f60c16 Mon Sep 17 00:00:00 2001
From: James Molloy <james.molloy@arm.com>
Date: Tue, 7 Jun 2016 13:10:14 +0000
Subject: [PATCH] [Thumb-1] Add optimized constant materialization for integers
 [256..512)

We can materialize these integers using a MOV; ADDi8 pair.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272007 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM/ARMISelDAGToDAG.cpp |  1 +
 lib/Target/ARM/ARMInstrThumb.td    | 12 ++++++++++++
 test/CodeGen/Thumb/constants.ll    | 11 +++++++++++
 3 files changed, 24 insertions(+)
 create mode 100644 test/CodeGen/Thumb/constants.ll

diff --git a/lib/Target/ARM/ARMISelDAGToDAG.cpp b/lib/Target/ARM/ARMISelDAGToDAG.cpp
index 0aacd674d62..cc835df15b3 100644
--- a/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -485,6 +485,7 @@ unsigned ARMDAGToDAGISel::ConstantMaterializationCost(unsigned Val) const {
   if (Subtarget->isThumb()) {
     if (Val <= 255) return 1;                               // MOV
     if (Subtarget->hasV6T2Ops() && Val <= 0xffff) return 1; // MOVW
+    if (Val <= 511) return 2;                               // MOV + ADDi8
     if (~Val <= 255) return 2;                              // MOV + MVN
     if (ARM_AM::isThumbImmShiftedVal(Val)) return 2;        // MOV + LSL
   } else {
diff --git a/lib/Target/ARM/ARMInstrThumb.td b/lib/Target/ARM/ARMInstrThumb.td
index 52a376cd8b6..e9b49f90ecb 100644
--- a/lib/Target/ARM/ARMInstrThumb.td
+++ b/lib/Target/ARM/ARMInstrThumb.td
@@ -66,6 +66,14 @@ def thumb_immshifted_shamt : SDNodeXForm<imm, [{
   return CurDAG->getTargetConstant(V, SDLoc(N), MVT::i32);
 }]>;
 
+def imm256_511 : ImmLeaf<i32, [{
+  return Imm >= 256 && Imm < 512;
+}]>;
+
+def thumb_imm256_511_addend : SDNodeXForm<imm, [{
+  return CurDAG->getTargetConstant(N->getZExtValue() - 255, SDLoc(N), MVT::i32);
+}]>;
+
 // Scaled 4 immediate.
 def t_imm0_1020s4_asmoperand: AsmOperandClass { let Name = "Imm0_1020s4"; }
 def t_imm0_1020s4 : Operand<i32> {
@@ -1489,6 +1497,10 @@ def : T1Pat<(i32 thumb_immshifted:$src),
 def : T1Pat<(i32 imm0_255_comp:$src),
             (tMVN (tMOVi8 (imm_comp_XFORM imm:$src)))>;
 
+def : T1Pat<(i32 imm256_511:$src),
+            (tADDi8 (tMOVi8 255),
+                    (thumb_imm256_511_addend imm:$src))>;
+
 // Pseudo instruction that combines ldr from constpool and add pc. This should
 // be expanded into two instructions late to allow if-conversion and
 // scheduling.
diff --git a/test/CodeGen/Thumb/constants.ll b/test/CodeGen/Thumb/constants.ll
new file mode 100644
index 00000000000..34c08139602
--- /dev/null
+++ b/test/CodeGen/Thumb/constants.ll
@@ -0,0 +1,11 @@
+; RUN: llc < %s -mtriple=thumbv7-linux-gnueabi -mcpu=cortex-m0 -verify-machineinstrs | FileCheck --check-prefix CHECK-T1 %s
+; RUN: llc < %s -mtriple=thumbv7-linux-gnueabi -mcpu=cortex-m3 -verify-machineinstrs | FileCheck --check-prefix CHECK-T2 %s
+
+; CHECK-T1-LABEL: @mov_and_add
+; CHECK-T2-LABEL: @mov_and_add
+; CHECK-T1: movs r0, #255
+; CHECK-T1: adds r0, #12
+; CHECK-T2: movw r0, #267
+define i32 @mov_and_add() {
+  ret i32 267
+}