diff -r f95d63e2154a -r ac637b7220d1 src/cpu/x86/vm/c1_LinearScan_x86.hpp
--- a/src/cpu/x86/vm/c1_LinearScan_x86.hpp	Tue Nov 23 13:22:55 2010 -0800
+++ b/src/cpu/x86/vm/c1_LinearScan_x86.hpp	Tue Nov 30 23:23:40 2010 -0800
@@ -31,18 +31,17 @@
   assert(FrameMap::rsp_opr->cpu_regnr() == 6, "wrong assumption below");
   assert(FrameMap::rbp_opr->cpu_regnr() == 7, "wrong assumption below");
   assert(reg_num >= 0, "invalid reg_num");
-
-  return reg_num < 6 || reg_num > 7;
 #else
-  // rsp and rbp, r10, r15 (numbers 6 ancd 7) are ignored
+  // rsp and rbp, r10, r15 (numbers [12,15]) are ignored
+  // r12 (number 11) is conditional on compressed oops.
+  assert(FrameMap::r12_opr->cpu_regnr() == 11, "wrong assumption below");
   assert(FrameMap::r10_opr->cpu_regnr() == 12, "wrong assumption below");
   assert(FrameMap::r15_opr->cpu_regnr() == 13, "wrong assumption below");
   assert(FrameMap::rsp_opr->cpu_regnrLo() == 14, "wrong assumption below");
   assert(FrameMap::rbp_opr->cpu_regnrLo() == 15, "wrong assumption below");
   assert(reg_num >= 0, "invalid reg_num");
-
-  return reg_num < 12 || reg_num > 15;
 #endif // _LP64
+  return reg_num <= FrameMap::last_cpu_reg() || reg_num >= pd_nof_cpu_regs_frame_map;
 }
 
 inline int LinearScan::num_physical_regs(BasicType type) {
@@ -104,7 +103,7 @@
   if (allocator()->gen()->is_vreg_flag_set(cur->reg_num(), LIRGenerator::byte_reg)) {
     assert(cur->type() != T_FLOAT && cur->type() != T_DOUBLE, "cpu regs only");
     _first_reg = pd_first_byte_reg;
-    _last_reg = pd_last_byte_reg;
+    _last_reg = FrameMap::last_byte_reg();
     return true;
   } else if ((UseSSE >= 1 && cur->type() == T_FLOAT) || (UseSSE >= 2 && cur->type() == T_DOUBLE)) {
     _first_reg = pd_first_xmm_reg;