S390: Optimize allocate sequence

Improve the S390 allocate sequence by:
- Keeping allocation limit in memory, and leverage compare RX-instr.
- Prefetching subsequent cache lines from allocation top.
- Optimizing object tagging with LA
- Optimizing increment for Fast-Allocate with ASI/AGSI

R=jyan@ca.ibm.com, michael_dawson@ca.ibm.com, bjaideep@ca.ibm.com
BUG=

Review-Url: https://codereview.chromium.org/2601563002
Cr-Commit-Position: refs/heads/master@{#41933}

src/s390/assembler-s390.cc

@@ -1337,6 +1337,7 @@ SI_FORM_EMIT(ni, NI)
 RI1_FORM_EMIT(nilh, NILH)
 RI1_FORM_EMIT(nill, NILL)
 RI1_FORM_EMIT(oill, OILL)
+RXY_FORM_EMIT(pfd, PFD)
 RXY_FORM_EMIT(slgf, SLGF)
 RXY_FORM_EMIT(strvh, STRVH)
 RXY_FORM_EMIT(strv, STRV)

src/s390/assembler-s390.h

@@ -987,6 +987,7 @@ class Assembler : public AssemblerBase {
   RI1_FORM(nilh);
   RI1_FORM(nill);
   RI1_FORM(oill);
+  RXY_FORM(pfd);
   RXE_FORM(sdb);
   RXY_FORM(slgf);
   RS1_FORM(srdl);

src/s390/disasm-s390.cc

@@ -1415,6 +1415,9 @@ bool Decoder::DecodeSixByte(Instruction* instr) {
     case SQDB:
       Format(instr, "sqdb\t'r1,'d1('r2d, 'r3)");
       break;
+    case PFD:
+      Format(instr, "pfd\t'm1,'d2('r2d,'r3)");
+      break;
     default:
       return false;
   }

src/s390/macro-assembler-s390.cc

@@ -1579,25 +1579,18 @@ void MacroAssembler::Allocate(int object_size, Register result,
 
   // Set up allocation top address register.
   Register top_address = scratch1;
-  // This code stores a temporary value in ip. This is OK, as the code below
-  // does not need ip for implicit literal generation.
-  Register alloc_limit = ip;
   Register result_end = scratch2;
   mov(top_address, Operand(allocation_top));
 
   if ((flags & RESULT_CONTAINS_TOP) == 0) {
     // Load allocation top into result and allocation limit into ip.
     LoadP(result, MemOperand(top_address));
-    LoadP(alloc_limit, MemOperand(top_address, kPointerSize));
   } else {
     if (emit_debug_code()) {
       // Assert that result actually contains top on entry.
-      LoadP(alloc_limit, MemOperand(top_address));
-      CmpP(result, alloc_limit);
+      CmpP(result, MemOperand(top_address));
       Check(eq, kUnexpectedAllocationTop);
     }
-    // Load allocation limit. Result already contains allocation top.
-    LoadP(alloc_limit, MemOperand(top_address, limit - top));
   }
 
   if ((flags & DOUBLE_ALIGNMENT) != 0) {
@@ -1611,7 +1604,7 @@ void MacroAssembler::Allocate(int object_size, Register result,
     Label aligned;
     beq(&aligned, Label::kNear);
     if ((flags & PRETENURE) != 0) {
-      CmpLogicalP(result, alloc_limit);
+      CmpLogicalP(result, MemOperand(top_address, limit - top));
       bge(gc_required);
     }
     mov(result_end, Operand(isolate()->factory()->one_pointer_filler_map()));
@@ -1621,27 +1614,24 @@ void MacroAssembler::Allocate(int object_size, Register result,
 #endif
   }
 
-  // Calculate new top and bail out if new space is exhausted. Use result
-  // to calculate the new top.
-  SubP(r0, alloc_limit, result);
-  if (is_int16(object_size)) {
-    CmpP(r0, Operand(object_size));
-    blt(gc_required);
   AddP(result_end, result, Operand(object_size));
-  } else {
-    mov(result_end, Operand(object_size));
-    CmpP(r0, result_end);
-    blt(gc_required);
-    AddP(result_end, result, result_end);
-  }
+
+  // Compare with allocation limit.
+  CmpLogicalP(result_end, MemOperand(top_address, limit - top));
+  bge(gc_required);
 
   if ((flags & ALLOCATION_FOLDING_DOMINATOR) == 0) {
     // The top pointer is not updated for allocation folding dominators.
     StoreP(result_end, MemOperand(top_address));
   }
 
+  // Prefetch the allocation_top's next cache line in advance to
+  // help alleviate potential cache misses.
+  // Mode 2 - Prefetch the data into a cache line for store access.
+  pfd(r2, MemOperand(result, 256));
+
   // Tag object.
-  AddP(result, result, Operand(kHeapObjectTag));
+  la(result, MemOperand(result, kHeapObjectTag));
 }
 
 void MacroAssembler::Allocate(Register object_size, Register result,
@@ -1676,24 +1666,17 @@ void MacroAssembler::Allocate(Register object_size, Register result,
 
   // Set up allocation top address and allocation limit registers.
   Register top_address = scratch;
-  // This code stores a temporary value in ip. This is OK, as the code below
-  // does not need ip for implicit literal generation.
-  Register alloc_limit = ip;
   mov(top_address, Operand(allocation_top));
 
   if ((flags & RESULT_CONTAINS_TOP) == 0) {
-    // Load allocation top into result and allocation limit into alloc_limit..
+    // Load allocation top into result
     LoadP(result, MemOperand(top_address));
-    LoadP(alloc_limit, MemOperand(top_address, kPointerSize));
   } else {
     if (emit_debug_code()) {
       // Assert that result actually contains top on entry.
-      LoadP(alloc_limit, MemOperand(top_address));
-      CmpP(result, alloc_limit);
+      CmpP(result, MemOperand(top_address));
       Check(eq, kUnexpectedAllocationTop);
     }
-    // Load allocation limit. Result already contains allocation top.
-    LoadP(alloc_limit, MemOperand(top_address, limit - top));
   }
 
   if ((flags & DOUBLE_ALIGNMENT) != 0) {
@@ -1707,7 +1690,7 @@ void MacroAssembler::Allocate(Register object_size, Register result,
     Label aligned;
     beq(&aligned, Label::kNear);
     if ((flags & PRETENURE) != 0) {
-      CmpLogicalP(result, alloc_limit);
+      CmpLogicalP(result, MemOperand(top_address, limit - top));
       bge(gc_required);
     }
     mov(result_end, Operand(isolate()->factory()->one_pointer_filler_map()));
@@ -1720,17 +1703,14 @@ void MacroAssembler::Allocate(Register object_size, Register result,
   // Calculate new top and bail out if new space is exhausted. Use result
   // to calculate the new top. Object size may be in words so a shift is
   // required to get the number of bytes.
-  SubP(r0, alloc_limit, result);
   if ((flags & SIZE_IN_WORDS) != 0) {
     ShiftLeftP(result_end, object_size, Operand(kPointerSizeLog2));
-    CmpP(r0, result_end);
-    blt(gc_required);
     AddP(result_end, result, result_end);
   } else {
-    CmpP(r0, object_size);
-    blt(gc_required);
     AddP(result_end, result, object_size);
   }
+  CmpLogicalP(result_end, MemOperand(top_address, limit - top));
+  bge(gc_required);
 
   // Update allocation top. result temporarily holds the new top.
   if (emit_debug_code()) {
@@ -1742,8 +1722,13 @@ void MacroAssembler::Allocate(Register object_size, Register result,
     StoreP(result_end, MemOperand(top_address));
   }
 
+  // Prefetch the allocation_top's next cache line in advance to
+  // help alleviate potential cache misses.
+  // Mode 2 - Prefetch the data into a cache line for store access.
+  pfd(r2, MemOperand(result, 256));
+
   // Tag object.
-  AddP(result, result, Operand(kHeapObjectTag));
+  la(result, MemOperand(result, kHeapObjectTag));
 }
 
 void MacroAssembler::FastAllocate(Register object_size, Register result,
@@ -1795,8 +1780,13 @@ void MacroAssembler::FastAllocate(Register object_size, Register result,
   }
   StoreP(result_end, MemOperand(top_address));
 
+  // Prefetch the allocation_top's next cache line in advance to
+  // help alleviate potential cache misses.
+  // Mode 2 - Prefetch the data into a cache line for store access.
+  pfd(r2, MemOperand(result, 256));
+
   // Tag object.
-  AddP(result, result, Operand(kHeapObjectTag));
+  la(result, MemOperand(result, kHeapObjectTag));
 }
 
 void MacroAssembler::FastAllocate(int object_size, Register result,
@@ -1837,14 +1827,24 @@ void MacroAssembler::FastAllocate(int object_size, Register result,
 #endif
   }
 
+  if (CpuFeatures::IsSupported(GENERAL_INSTR_EXT) && is_int8(object_size)) {
+    // Update allocation top.
+    AddP(MemOperand(top_address), Operand(object_size));
+  } else {
     // Calculate new top using result.
     AddP(result_end, result, Operand(object_size));
 
-  // The top pointer is not updated for allocation folding dominators.
+    // Update allocation top.
     StoreP(result_end, MemOperand(top_address));
+  }
+
+  // Prefetch the allocation_top's next cache line in advance to
+  // help alleviate potential cache misses.
+  // Mode 2 - Prefetch the data into a cache line for store access.
+  pfd(r2, MemOperand(result, 256));
 
   // Tag object.
-  AddP(result, result, Operand(kHeapObjectTag));
+  la(result, MemOperand(result, kHeapObjectTag));
 }
 
 void MacroAssembler::CompareObjectType(Register object, Register map,

src/s390/simulator-s390.cc

@@ -11152,9 +11152,9 @@ EVALUATE(CGH) {
 }
 
 EVALUATE(PFD) {
-  UNIMPLEMENTED();
+  DCHECK_OPCODE(PFD);
   USE(instr);
-  return 0;
+  return 6;
 }
 
 EVALUATE(STRV) {