8372701: Randomized profile counters

src/hotspot/cpu/aarch64/assembler_aarch64.hpp

@@ -148,6 +148,9 @@ constexpr Register rdispatch     = r21; // dispatch table base
 constexpr Register esp           = r20; // Java expression stack pointer
 constexpr Register r19_sender_sp = r19; // sender's SP while in interpreter
 
+// State for randomized profile counters. Used by C1.
+extern Register r_profile_rng;
+
 // Preserved predicate register with all elements set TRUE.
 constexpr PRegister ptrue = p7;
 
@@ -3227,11 +3230,11 @@ template<typename R, typename... Rx>
 #undef INSN
 
   // CRC32 instructions
-#define INSN(NAME, c, sf, sz)                                             \
-  void NAME(Register Rd, Register Rn, Register Rm) {                      \
-    starti;                                                               \
-    f(sf, 31), f(0b0011010110, 30, 21), f(0b010, 15, 13), f(c, 12);       \
-    f(sz, 11, 10), rf(Rm, 16), rf(Rn, 5), rf(Rd, 0);                      \
+#define INSN(NAME, c, sf, sz)                                           \
+  void NAME(Register Rd, Register Rn, Register Rm) {                    \
+    starti;                                                             \
+    f(sf, 31), f(0b0011010110, 30, 21), f(0b010, 15, 13), f(c, 12);     \
+    f(sz, 11, 10), zrf(Rm, 16), rf(Rn, 5), rf(Rd, 0);                   \
   }
 
   INSN(crc32b,  0, 0, 0b00);

src/hotspot/cpu/aarch64/c1_FrameMap_aarch64.cpp

@@ -191,24 +191,33 @@ void FrameMap::initialize() {
   map_register(i, r23); r23_opr = LIR_OprFact::single_cpu(i); i++;
   map_register(i, r24); r24_opr = LIR_OprFact::single_cpu(i); i++;
   map_register(i, r25); r25_opr = LIR_OprFact::single_cpu(i); i++;
-  map_register(i, r26); r26_opr = LIR_OprFact::single_cpu(i); i++;
 
-  // r27 is allocated conditionally. With compressed oops it holds
-  // the heapbase value and is not visible to the allocator.
-  bool preserve_rheapbase = i >= nof_caller_save_cpu_regs();
-  if (!preserve_rheapbase) {
-    map_register(i, r27); r27_opr = LIR_OprFact::single_cpu(i); i++; // rheapbase
+  auto remaining = RegSet::of(r26, r27);
+
+  if (UseCompressedOops && (CompressedOops::base() != nullptr)) {
+    // r27 is allocated conditionally. With compressed oops it holds
+    // the heapbase value and is not visible to the allocator.
+    remaining -= r27;
+  }
+
+  if (ProfileCaptureRatio > 1) {
+    // Use the highest remaining register for r_profile_rng.
+    r_profile_rng = *remaining.rbegin();
+    remaining -= r_profile_rng;
+  }
+
+  if (remaining.contains(r26)) {
+    map_register(i, r26); r26_opr = LIR_OprFact::single_cpu(i); i++;
+  }
+  if (remaining.contains(r27)) {
+    map_register(i, r27); r27_opr = LIR_OprFact::single_cpu(i); i++;
   }
 
   if(!PreserveFramePointer) {
     map_register(i, r29); r29_opr = LIR_OprFact::single_cpu(i); i++;
   }
 
   // The unallocatable registers are at the end
-
-  if (preserve_rheapbase) {
-    map_register(i, r27); r27_opr = LIR_OprFact::single_cpu(i); i++; // rheapbase
-  }
   map_register(i, r28); r28_opr = LIR_OprFact::single_cpu(i); i++; // rthread
   if(PreserveFramePointer) {
     map_register(i, r29); r29_opr = LIR_OprFact::single_cpu(i); i++; // rfp

src/hotspot/cpu/aarch64/c1_FrameMap_aarch64.hpp

@@ -147,6 +147,11 @@
       range -= 1;
     }
 
+    // Use r26 for randomized profile captures.
+    if (ProfileCaptureRatio > 1) {
+      range -= 1;
+    }
+
     // r29 is not allocatable when PreserveFramePointer is on,
     // but fp saving is handled in MacroAssembler::build_frame()/remove_frame()
     if (exclude_fp) {