Port count-based profiler to ARM

src/arm/deoptimizer-arm.cc

Index: src/arm/deoptimizer-arm.cc
diff --git a/src/arm/deoptimizer-arm.cc b/src/arm/deoptimizer-arm.cc
index d9a4d4b0f41e3083a39f4c3a10486ae3cd5f2528..a9fa061815eb1ebb9a701d7275624b490e4da0c0 100644
--- a/src/arm/deoptimizer-arm.cc
+++ b/src/arm/deoptimizer-arm.cc
@@ -108,6 +108,10 @@ void Deoptimizer::DeoptimizeFunction(JSFunction* function) {
 }
 
 
+static const int32_t kBranchBeforeStackCheck = 0x2a000001;
+static const int32_t kBranchBeforeInterrupt =  0x5a000004;

[Erik Corry, 2012/03/23 09:55:53]

There is a bunch of these in assembler-arm.h eg kMovLrPc.  I think these should
go there too.

[Jakob Kummerow, 2012/03/23 12:07:32]

I disagree. They contain condition codes and jump offsets, and are therefore
strictly tied to this usage site. I don't think they can ever be shared, so IMHO
pulling them up to a more global place reduces readability/understandability of
this code here.

I could split the definitions:
/*assembler-arm.{h|cc}*/
const Instr kBcs = 0x2a000000;
const Instr kBpl = 0x5a000000;
/*here/*
static const int32_t kBranchBeforeStackCheck = kBce | 1;
static const int32_t kBranchBeforeInterrupt = kBpl | 4;

Would you like that better?

+
+
 void Deoptimizer::PatchStackCheckCodeAt(Code* unoptimized_code,
                                         Address pc_after,
                                         Code* check_code,
@@ -122,6 +126,13 @@ void Deoptimizer::PatchStackCheckCodeAt(Code* unoptimized_code,
       (al | B24 | B21 | 15*B16 | 15*B12 | 15*B8 | BLX | ip.code()));
   ASSERT(Assembler::IsLdrPcImmediateOffset(
       Assembler::instr_at(pc_after - 2 * kInstrSize)));
+  if (FLAG_count_based_interrupts) {
+    ASSERT_EQ(kBranchBeforeInterrupt,
+              Memory::int32_at(pc_after - 3 * kInstrSize));
+  } else {
+    ASSERT_EQ(kBranchBeforeStackCheck,
+              Memory::int32_at(pc_after - 3 * kInstrSize));
+  }
 
   // We patch the code to the following form:
   //  e1 5d 00 0c       cmp sp, <limit>
@@ -155,13 +166,22 @@ void Deoptimizer::RevertStackCheckCodeAt(Code* unoptimized_code,
                                          Code* check_code,
                                          Code* replacement_code) {
   const int kInstrSize = Assembler::kInstrSize;
-  ASSERT(Memory::uint32_at(pc_after - kInstrSize) == 0xe12fff3c);
-  ASSERT(Memory::uint8_at(pc_after - kInstrSize - 1) == 0xe5);
-  ASSERT(Memory::uint8_at(pc_after - kInstrSize - 2) == 0x9f);
+  ASSERT(Memory::int32_at(pc_after - kInstrSize) ==
+      (al | B24 | B21 | 15*B16 | 15*B12 | 15*B8 | BLX | ip.code()));

[Erik Corry, 2012/03/23 09:55:53]

What is this instruction?

[Jakob Kummerow, 2012/03/23 12:07:32]

"blx ip", copied from above in the interest of unification, see also the
comments in PatchStackCheckCodeAt listing the relevant machine code.
Since this instruction is not specific to this site, I've moved it to
assembler-arm.h.

+  ASSERT(Assembler::IsLdrPcImmediateOffset(
+      Assembler::instr_at(pc_after - 2 * kInstrSize)));
 
   // Replace NOP with conditional jump.
   CodePatcher patcher(pc_after - 3 * kInstrSize, 1);
-  patcher.masm()->b(+4, cs);
+  if (FLAG_count_based_interrupts) {
+    patcher.masm()->b(+16, pl);
+    ASSERT_EQ(kBranchBeforeInterrupt,
+              Memory::int32_at(pc_after - 3 * kInstrSize));
+  } else {
+    patcher.masm()->b(+4, cs);
+    ASSERT_EQ(kBranchBeforeStackCheck,
+              Memory::int32_at(pc_after - 3 * kInstrSize));
+  }
 
   // Replace the stack check address in the constant pool
   // with the entry address of the replacement code.