A few fixes for ARMv5TE.

runtime/vm/assembler_arm.cc

Index: runtime/vm/assembler_arm.cc
===================================================================
--- runtime/vm/assembler_arm.cc	(revision 44777)
+++ runtime/vm/assembler_arm.cc	(working copy)
@@ -435,7 +435,6 @@
 
 void Assembler::smull(Register rd_lo, Register rd_hi,
                       Register rn, Register rm, Condition cond) {
-  ASSERT(TargetCPUFeatures::arm_version() == ARMv7);
   // Assembler registers rd_lo, rd_hi, rn, rm are encoded as rd, rn, rm, rs.
   EmitMulOp(cond, B23 | B22, rd_lo, rd_hi, rn, rm);
 }
@@ -540,15 +539,27 @@
 }
 
 
-void Assembler::ldrd(Register rd, Address ad, Condition cond) {
+void Assembler::ldrd(Register rd, Register rn, int32_t offset, Condition cond) {
   ASSERT((rd % 2) == 0);
-  EmitMemOpAddressMode3(cond, B7 | B6 | B4, rd, ad);
+  if (TargetCPUFeatures::arm_version() == ARMv5TE) {
+    const Register rd2 = static_cast<Register>(static_cast<int32_t>(rd) + 1);
+    ldr(rd, Address(rn, offset), cond);
+    ldr(rd2, Address(rn, offset + kWordSize), cond);
+  } else {
+    EmitMemOpAddressMode3(cond, B7 | B6 | B4, rd, Address(rn, offset));
+  }
 }
 
 
-void Assembler::strd(Register rd, Address ad, Condition cond) {
+void Assembler::strd(Register rd, Register rn, int32_t offset, Condition cond) {
   ASSERT((rd % 2) == 0);
-  EmitMemOpAddressMode3(cond, B7 | B6 | B5 | B4, rd, ad);
+  if (TargetCPUFeatures::arm_version() == ARMv5TE) {
+    const Register rd2 = static_cast<Register>(static_cast<int32_t>(rd) + 1);
+    str(rd, Address(rn, offset), cond);
+    str(rd2, Address(rn, offset + kWordSize), cond);
+  } else {
+    EmitMemOpAddressMode3(cond, B7 | B6 | B5 | B4, rd, Address(rn, offset));
+  }
 }
 
 
@@ -556,11 +567,6 @@
                     Condition cond) {
   ASSERT(regs != 0);
   EmitMultiMemOp(cond, am, true, base, regs);
-  if (TargetCPUFeatures::arm_version() == ARMv5TE) {
-    // On ARMv5, touching a "banked" register after an ldm gives undefined
-    // behavior, so we just add a nop here to make that case easy to avoid.
-    nop();
-  }
 }
 
 
@@ -568,11 +574,6 @@
                     Condition cond) {
   ASSERT(regs != 0);
   EmitMultiMemOp(cond, am, false, base, regs);
-  if (TargetCPUFeatures::arm_version() == ARMv5TE) {
-    // On ARMv5, touching a "banked" register after an stm gives undefined
-    // behavior, so we just add a nop here to make that case easy to avoid.
-    nop();
-  }
 }
 
 
@@ -1676,10 +1677,10 @@
     ASSERT(base != value_odd);
     Operand shadow(GetVerifiedMemoryShadow());
     add(base, base, shadow, cond);
-    strd(value_even, Address(base, offset), cond);
+    strd(value_even, base, offset, cond);
     sub(base, base, shadow, cond);
   }
-  strd(value_even, Address(base, offset), cond);
+  strd(value_even, base, offset, cond);
 }
 
 
@@ -2794,7 +2795,7 @@
       ldr(reg, Address(base, offset), cond);
       break;
     case kWordPair:
-      ldrd(reg, Address(base, offset), cond);
+      ldrd(reg, base, offset, cond);
       break;
     default:
       UNREACHABLE();
@@ -2826,7 +2827,7 @@
       str(reg, Address(base, offset), cond);
       break;
     case kWordPair:
-      strd(reg, Address(base, offset), cond);
+      strd(reg, base, offset, cond);
       break;
     default:
       UNREACHABLE();
@@ -3132,60 +3133,6 @@
 }
 
 
-// If we aren't on ARMv7, there is no smull, and we have to check for overflow
-// manually.
-void Assembler::CheckMultSignedOverflow(Register left,
-                                        Register right,
-                                        Register tmp,
-                                        DRegister dtmp0, DRegister dtmp1,
-                                        Label* overflow) {
-  Label done, left_neg, left_pos_right_neg, left_neg_right_pos;
-
-  CompareImmediate(left, 0);
-  b(&left_neg, LT);
-  b(&done, EQ);
-  CompareImmediate(right, 0);
-  b(&left_pos_right_neg, LT);
-  b(&done, EQ);
-
-  // Both positive.
-  LoadImmediate(tmp, INT_MAX);
-  IntegerDivide(tmp, tmp, left, dtmp0, dtmp1);
-  cmp(tmp, Operand(right));
-  b(overflow, LT);
-  b(&done);
-
-  // left positive, right non-positive.
-  Bind(&left_pos_right_neg);
-  LoadImmediate(tmp, INT_MIN);
-  IntegerDivide(tmp, tmp, left, dtmp0, dtmp1);
-  cmp(tmp, Operand(right));
-  b(overflow, GT);
-  b(&done);
-
-  Bind(&left_neg);
-  CompareImmediate(right, 0);
-  b(&left_neg_right_pos, GT);
-  b(&done, EQ);
-
-  // both negative.
-  LoadImmediate(tmp, INT_MAX);
-  IntegerDivide(tmp, tmp, left, dtmp0, dtmp1);
-  cmp(tmp, Operand(right));
-  b(overflow, GT);
-  b(&done);
-
-  // left non-positive, right positive.
-  Bind(&left_neg_right_pos);
-  LoadImmediate(tmp, INT_MIN);
-  IntegerDivide(tmp, tmp, right, dtmp0, dtmp1);
-  cmp(tmp, Operand(left));
-  b(overflow, GT);
-
-  Bind(&done);
-}
-
-
 static int NumRegsBelowFP(RegList regs) {
   int count = 0;
   for (int i = 0; i < FP; i++) {
@@ -3323,7 +3270,11 @@
 // optimized function and there may be extra space for spill slots to
 // allocate. We must also set up the pool pointer for the function.
 void Assembler::EnterOsrFrame(intptr_t extra_size) {
-  const intptr_t offset = CodeSize();
+  // The offset for the PC marker is adjusted by the difference in PC offset
+  // between stores and other instructions. In particular, on some ARMv5's the
+  // PC offset for stores is 12 and the offset in other instructions is 8.
+  const intptr_t offset = CodeSize() -
+      (TargetCPUFeatures::store_pc_read_offset() - Instr::kPCReadOffset);

[Vyacheslav Egorov (Google), 2015/03/31 08:05:30]

I find this comment and expression really confusing because store_pc_read_offset
does not explicitly surface in any expression below (instead it affects
EnterDartFrame above).

How about rewriting this expression to 

  CodeSize() + Instr::kPCReadOffset - EntryPointToPcMarkerOffset()

I think that'd be much easier to figure out.

Then the comment can just say that mov(IP, Operand(PC)) loads PC +
Instr::kPCRead (8)

 
   Comment("EnterOsrFrame");
   mov(IP, Operand(PC));