Reland - Arm64: Ensure that csp is always aligned to 16 byte values even if jssp is not.

src/arm64/macro-assembler-arm64-inl.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_ARM64_MACRO_ASSEMBLER_ARM64_INL_H_
 #define V8_ARM64_MACRO_ASSEMBLER_ARM64_INL_H_
 
 #include <ctype.h>
 
 #include "v8globals.h"
@@ skipping 1228 matching lines @@
 
 void MacroAssembler::Uxtw(const Register& rd, const Register& rn) {
   ASSERT(allow_macro_instructions_);
   ASSERT(!rd.IsZero());
   uxtw(rd, rn);
 }
 
 
 void MacroAssembler::BumpSystemStackPointer(const Operand& space) {
   ASSERT(!csp.Is(sp_));
-  // TODO(jbramley): Several callers rely on this not using scratch registers,
-  // so we use the assembler directly here. However, this means that large
-  // immediate values of 'space' cannot be handled cleanly. (Only 24-bits
-  // immediates or values of 'space' that can be encoded in one instruction are
-  // accepted.) Once we implement our flexible scratch register idea, we could
-  // greatly simplify this function.
-  InstructionAccurateScope scope(this);
-  if ((space.IsImmediate()) && !is_uint12(space.immediate())) {
-    // The subtract instruction supports a 12-bit immediate, shifted left by
-    // zero or 12 bits. So, in two instructions, we can subtract any immediate
-    // between zero and (1 << 24) - 1.
-    int64_t imm = space.immediate();
+  if (!TmpList()->IsEmpty()) {
+    if (CpuFeatures::IsSupported(ALWAYS_ALIGN_CSP)) {
+      UseScratchRegisterScope temps(this);
+      Register temp = temps.AcquireX();
+      Sub(temp, StackPointer(), space);
+      Bic(csp, temp, 0xf);
+    } else {
+      Sub(csp, StackPointer(), space);
+    }
+  } else {
+    // TODO(jbramley): Several callers rely on this not using scratch
+    // registers, so we use the assembler directly here. However, this means
+    // that large immediate values of 'space' cannot be handled cleanly. (Only
+    // 24-bits immediates or values of 'space' that can be encoded in one
+    // instruction are accepted.) Once we implement our flexible scratch
+    // register idea, we could greatly simplify this function.
+    InstructionAccurateScope scope(this);
+    ASSERT(space.IsImmediate());
+    // Align to 16 bytes.
+    uint64_t imm = RoundUp(space.immediate(), 0x10);
     ASSERT(is_uint24(imm));
 
-    int64_t imm_top_12_bits = imm >> 12;
-    sub(csp, StackPointer(), imm_top_12_bits << 12);
-    imm -= imm_top_12_bits << 12;
+    Register source = StackPointer();
+    if (CpuFeatures::IsSupported(ALWAYS_ALIGN_CSP)) {
+      bic(csp, source, 0xf);
+      source = csp;
+    }
+    if (!is_uint12(imm)) {
+      int64_t imm_top_12_bits = imm >> 12;
+      sub(csp, source, imm_top_12_bits << 12);
+      source = csp;
+      imm -= imm_top_12_bits << 12;
+    }
     if (imm > 0) {
-      sub(csp, csp, imm);
+      sub(csp, source, imm);
     }
-  } else {
-    sub(csp, StackPointer(), space);
   }
+  // TODO(rmcilroy): Uncomment when Debug::PrepareForBreakPoints issue is
+  //                 resolved.
+  // AssertStackConsistency(true);

[rmcilroy, 2014/05/07 18:08:21]

If I enable this I get the following assert in debug-multiple-breakpoints.js on
a nosnapshot build.  I've replaced this with an equivalent number of nop()
instructions and still got the same result, so this looks like an unrelated
failure which I am tickling by changing the amount of code generated.  Any ideas
Ulan?
 

./out/arm64.debug/d8 --test --random-seed=1269372994 --stress-opt --always-opt
--nohard-abort --nodead-code-elimination --nofold-constants
--enable-slow-asserts --debug-code --verify-heap --expose-debug-as debug
test/mjsunit/mjsunit.js test/mjsunit/debug-multiple-breakpoints.js
============ Stress 1/2 ============
============ Stress 2/2 ============


#
# Fatal error in ../src/debug.cc, line 2041
# CHECK_EQ(Code::FUNCTION, function->code()->kind()) failed
#   Expected: 0
#   Found: 4
#

==== C stack trace ===============================

 1: V8_Fatal
 2: CheckEqualsHelper(char const*, int, char const*, int, char const*, int)
 3:
v8::internal::Debug::MaybeRecompileFunctionForDebugging(v8::internal::Handle<v8::internal::JSFunction>)
 4: v8::internal::Debug::PrepareForBreakPoints()
 5:
v8::internal::Debug::SetBreakPointForScript(v8::internal::Handle<v8::internal::Script>,
v8::internal::Handle<v8::internal::Object>, int*,
v8::internal::BreakPositionAlignment)
 6: ??
 7: v8::internal::Runtime_SetScriptBreakPoint(int, v8::internal::Object**,
v8::internal::Isolate*)
 8: v8::internal::Simulator::DoRuntimeCall(v8::internal::Instruction*)
 9: v8::internal::Simulator::VisitException(v8::internal::Instruction*)
10:
v8::internal::Decoder<v8::internal::Simulator>::DecodeBranchSystemException(v8::internal::Instruction*)
11:
v8::internal::Decoder<v8::internal::Simulator>::Decode(v8::internal::Instruction*)
12: v8::internal::Simulator::ExecuteInstruction()
13: v8::internal::Simulator::Run()
14: v8::internal::Simulator::CheckPCSComplianceAndRun()
15: v8::internal::Simulator::CallVoid(unsigned char*,
v8::internal::Simulator::CallArgument*)
16: v8::internal::Simulator::CallInt64(unsigned char*,
v8::internal::Simulator::CallArgument*)
17: v8::internal::Simulator::CallJS(unsigned char*, unsigned char*,
v8::internal::JSFunction*, v8::internal::Object*, long, v8::internal::Object***)
18: ??
19: v8::internal::Execution::Call(v8::internal::Isolate*,
v8::internal::Handle<v8::internal::Object>,
v8::internal::Handle<v8::internal::Object>, int,
v8::internal::Handle<v8::internal::Object>*, bool)
20: v8::Script::Run()
21: v8::Shell::ExecuteString(v8::Isolate*, v8::Handle<v8::String>,
v8::Handle<v8::Value>, bool, bool)
22: v8::SourceGroup::Execute(v8::Isolate*)
23: v8::Shell::RunMain(v8::Isolate*, int, char**)
24: v8::Shell::Main(int, char**)
25: main
26: __libc_start_main
27: ??
Aborted (core dumped)

 }
 
 
+void MacroAssembler::SyncSystemStackPointer() {
+  ASSERT(emit_debug_code());
+  ASSERT(!csp.Is(sp_));
+  { InstructionAccurateScope scope(this);
+    if (CpuFeatures::IsSupported(ALWAYS_ALIGN_CSP)) {
+      bic(csp, StackPointer(), 0xf);
+    } else {
+      mov(csp, StackPointer());
+    }
+  }
+  AssertStackConsistency(true);
+}
+
+
 void MacroAssembler::InitializeRootRegister() {
   ExternalReference roots_array_start =
       ExternalReference::roots_array_start(isolate());
   Mov(root, Operand(roots_array_start));
 }
 
 
 void MacroAssembler::SmiTag(Register dst, Register src) {
   ASSERT(dst.Is64Bits() && src.Is64Bits());
   Lsl(dst, src, kSmiShift);
@@ skipping 248 matching lines @@
   }
 
   Add(StackPointer(), StackPointer(), size);
 
   if (csp.Is(StackPointer())) {
     ASSERT(size % 16 == 0);
   } else if (emit_debug_code()) {
     // It is safe to leave csp where it is when unwinding the JavaScript stack,
     // but if we keep it matching StackPointer, the simulator can detect memory
     // accesses in the now-free part of the stack.
-    Mov(csp, StackPointer());
+    SyncSystemStackPointer();
   }
 }
 
 
 void MacroAssembler::Drop(const Register& count, uint64_t unit_size) {
   if (unit_size == 0) return;
   ASSERT(IsPowerOf2(unit_size));
 
   const int shift = CountTrailingZeros(unit_size, kXRegSizeInBits);
   const Operand size(count, LSL, shift);
 
   if (size.IsZero()) {
     return;
   }
 
   Add(StackPointer(), StackPointer(), size);
 
   if (!csp.Is(StackPointer()) && emit_debug_code()) {
     // It is safe to leave csp where it is when unwinding the JavaScript stack,
     // but if we keep it matching StackPointer, the simulator can detect memory
     // accesses in the now-free part of the stack.
-    Mov(csp, StackPointer());
+    SyncSystemStackPointer();
   }
 }
 
 
 void MacroAssembler::DropBySMI(const Register& count_smi, uint64_t unit_size) {
   ASSERT(unit_size == 0 || IsPowerOf2(unit_size));
   const int shift = CountTrailingZeros(unit_size, kXRegSizeInBits) - kSmiShift;
   const Operand size(count_smi,
                      (shift >= 0) ? (LSL) : (LSR),
                      (shift >= 0) ? (shift) : (-shift));
 
   if (size.IsZero()) {
     return;
   }
 
   Add(StackPointer(), StackPointer(), size);
 
   if (!csp.Is(StackPointer()) && emit_debug_code()) {
     // It is safe to leave csp where it is when unwinding the JavaScript stack,
     // but if we keep it matching StackPointer, the simulator can detect memory
     // accesses in the now-free part of the stack.
-    Mov(csp, StackPointer());
+    SyncSystemStackPointer();
   }
 }
 
 
 void MacroAssembler::CompareAndBranch(const Register& lhs,
                                       const Operand& rhs,
                                       Condition cond,
                                       Label* label) {
   if (rhs.IsImmediate() && (rhs.immediate() == 0) &&
       ((cond == eq) || (cond == ne))) {
@@ skipping 63 matching lines @@
   // characters are reserved for controlling features of the instrumentation.
   ASSERT(isprint(marker_name[0]) && isprint(marker_name[1]));
 
   InstructionAccurateScope scope(this, 1);
   movn(xzr, (marker_name[1] << 8) | marker_name[0]);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM64_MACRO_ASSEMBLER_ARM64_INL_H_