Clean up ARM mov 32bit immediate code in preparation for out of line constant pool.

R=rodolph.perfetta@arm.com, ulan@chromium.org

Review URL: https://codereview.chromium.org/138503002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19823 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/assembler-arm.cc

@@ -1059,14 +1059,19 @@ bool Operand::must_output_reloc_info(const Assembler* assembler) const {
 }
 
 
-static bool use_movw_movt(const Operand& x, const Assembler* assembler) {
-  if (Assembler::use_immediate_embedded_pointer_loads(assembler)) {
+static bool use_mov_immediate_load(const Operand& x,
+                                   const Assembler* assembler) {
+  if (CpuFeatures::IsSupported(MOVW_MOVT_IMMEDIATE_LOADS) &&
+             (assembler == NULL || !assembler->predictable_code_size())) {
+    // Prefer movw / movt to constant pool if it is more efficient on the CPU.
     return true;
-  }
-  if (x.must_output_reloc_info(assembler)) {
+  } else if (x.must_output_reloc_info(assembler)) {
+    // Prefer constant pool if data is likely to be patched.
     return false;
+  } else {
+    // Otherwise, use immediate load if movw / movt is available.
+    return CpuFeatures::IsSupported(ARMv7);
   }
-  return CpuFeatures::IsSupported(ARMv7);
 }
 
 
@@ -1080,7 +1085,7 @@ bool Operand::is_single_instruction(const Assembler* assembler,
     // constant pool is required. For a mov instruction not setting the
     // condition code additional instruction conventions can be used.
     if ((instr & ~kCondMask) == 13*B21) {  // mov, S not set
-      return !use_movw_movt(*this, assembler);
+      return !use_mov_immediate_load(*this, assembler);
     } else {
       // If this is not a mov or mvn instruction there will always an additional
       // instructions - either mov or ldr. The mov might actually be two
@@ -1096,12 +1101,11 @@ bool Operand::is_single_instruction(const Assembler* assembler,
 }
 
 
-void Assembler::move_32_bit_immediate(Condition cond,
-                                      Register rd,
-                                      SBit s,
-                                      const Operand& x) {
-  if (rd.code() != pc.code() && s == LeaveCC) {
-    if (use_movw_movt(x, this)) {
+void Assembler::move_32_bit_immediate(Register rd,
+                                      const Operand& x,
+                                      Condition cond) {
+  if (rd.code() != pc.code()) {
+    if (use_mov_immediate_load(x, this)) {
       if (x.must_output_reloc_info(this)) {
         RecordRelocInfo(x.rmode_, x.imm32_, DONT_USE_CONSTANT_POOL);
         // Make sure the movw/movt doesn't get separated.
@@ -1138,20 +1142,9 @@ void Assembler::addrmod1(Instr instr,
       CHECK(!rn.is(ip));  // rn should never be ip, or will be trashed
       Condition cond = Instruction::ConditionField(instr);
       if ((instr & ~kCondMask) == 13*B21) {  // mov, S not set
-        move_32_bit_immediate(cond, rd, LeaveCC, x);
+        move_32_bit_immediate(rd, x, cond);
       } else {
-        if ((instr & kMovMvnMask) == kMovMvnPattern) {
-          // Moves need to use a constant pool entry.
-          RecordRelocInfo(x.rmode_, x.imm32_, USE_CONSTANT_POOL);
-          ldr(ip, MemOperand(pc, 0), cond);
-        } else if (x.must_output_reloc_info(this)) {
-          // Otherwise, use most efficient form of fetching from constant pool.
-          move_32_bit_immediate(cond, ip, LeaveCC, x);
-        } else {
-          // If this is not a mov or mvn instruction we may still be able to
-          // avoid a constant pool entry by using mvn or movw.
-          mov(ip, x, LeaveCC, cond);
-        }
+        mov(ip, x, LeaveCC, cond);
         addrmod1(instr, rn, rd, Operand(ip));
       }
       return;
@@ -1819,8 +1812,7 @@ void Assembler::msr(SRegisterFieldMask fields, const Operand& src,
     if (src.must_output_reloc_info(this) ||
         !fits_shifter(src.imm32_, &rotate_imm, &immed_8, NULL)) {
       // Immediate operand cannot be encoded, load it first to register ip.
-      RecordRelocInfo(src.rmode_, src.imm32_);
-      ldr(ip, MemOperand(pc, 0), cond);
+      move_32_bit_immediate(ip, src);
       msr(fields, Operand(ip), cond);
       return;
     }

src/arm/assembler-arm.h

@@ -1292,12 +1292,6 @@ class Assembler : public AssemblerBase {
   // Jump unconditionally to given label.
   void jmp(Label* L) { b(L, al); }
 
-  static bool use_immediate_embedded_pointer_loads(
-      const Assembler* assembler) {
-    return CpuFeatures::IsSupported(MOVW_MOVT_IMMEDIATE_LOADS) &&
-        (assembler == NULL || !assembler->predictable_code_size());
-  }
-
   // Check the code size generated from label to here.
   int SizeOfCodeGeneratedSince(Label* label) {
     return pc_offset() - label->pos();
@@ -1565,10 +1559,9 @@ class Assembler : public AssemblerBase {
   inline void emit(Instr x);
 
   // 32-bit immediate values
-  void move_32_bit_immediate(Condition cond,
-                             Register rd,
-                             SBit s,
-                             const Operand& x);
+  void move_32_bit_immediate(Register rd,
+                             const Operand& x,
+                             Condition cond = al);
 
   // Instruction generation
   void addrmod1(Instr instr, Register rn, Register rd, const Operand& x);

test/cctest/test-disasm-arm.cc

@@ -272,10 +272,10 @@ TEST(Type0) {
     // We only disassemble one instruction so the eor instruction is not here.
     COMPARE(eor(r5, r4, Operand(0x1234), LeaveCC, ne),
             "1301c234       movwne ip, #4660");
-    // Movw can't do setcc so we don't get that here.  Mov immediate with setcc
-    // is pretty strange anyway.
+    // Movw can't do setcc, so first move to ip, then the following instruction
+    // moves to r5.  Mov immediate with setcc is pretty strange anyway.
     COMPARE(mov(r5, Operand(0x01234), SetCC, ne),
-            "159fc000       ldrne ip, [pc, #+0]");
+            "1301c234       movwne ip, #4660");
     // Emit a literal pool now, otherwise this could be dumped later, in the
     // middle of a different test.
     EMIT_PENDING_LITERALS();