[aarch64-port-dev ] Fix overflow with large page sizes

[Andrew Haley]

With large page sizes a calculation overflows the immediate
field size.  Fixed thusly.

Andrew.



# HG changeset patch
# User aph
# Date 1374835632 -3600
# Node ID cdd6408be9aa2c1617fd48ba800b8317d28cea28
# Parent  d9453f3218eefad8a982bb928bbdfcbc727cb2b0
Fix overflow with large page sizes.

diff -r d9453f3218ee -r cdd6408be9aa src/cpu/aarch64/vm/macroAssembler_aarch64.cpp
--- a/src/cpu/aarch64/vm/macroAssembler_aarch64.cpp	Thu Jul 25 18:31:25 2013 +0100
+++ b/src/cpu/aarch64/vm/macroAssembler_aarch64.cpp	Fri Jul 26 11:47:12 2013 +0100
@@ -1517,7 +1517,7 @@
 }

 // If a constant does not fit in an immediate field, generate some
-// number of MOV instructions and then perform the operation
+// number of MOV instructions and then perform the operation.
 void MacroAssembler::wrap_add_sub_imm_insn(Register Rd, Register Rn, unsigned imm,
 					   add_sub_imm_insn insn1,
 					   add_sub_reg_insn insn2) {
@@ -1525,6 +1525,7 @@
     (this->*insn1)(Rd, Rn, imm);
   } else {
     assert_different_registers(Rd, Rn);
+    assert(Rd != zr, "overflow in immediate operand");
     mov(Rd, (uint64_t)imm);
     (this->*insn2)(Rd, Rn, Rd, LSL, 0);
   }
diff -r d9453f3218ee -r cdd6408be9aa src/cpu/aarch64/vm/templateInterpreter_aarch64.cpp
--- a/src/cpu/aarch64/vm/templateInterpreter_aarch64.cpp	Thu Jul 25 18:31:25 2013 +0100
+++ b/src/cpu/aarch64/vm/templateInterpreter_aarch64.cpp	Fri Jul 26 11:47:12 2013 +0100
@@ -474,7 +474,12 @@
   // see if the frame is greater than one page in size. If so,
   // then we need to verify there is enough stack space remaining
   // for the additional locals.
-  __ cmp(r3, (page_size - overhead_size) / Interpreter::stackElementSize);
+  //
+  // Note that we use SUBS rather than CMP here because the immediate
+  // field of this instruction may overflow.  SUBS can cope with this
+  // because it is a macro that will expand to some number of MOV
+  // instructions and a register operation.
+  __ subs(rscratch1, r3, (page_size - overhead_size) / Interpreter::stackElementSize);
   __ br(Assembler::LS, after_frame_check);

   // compute rsp as if this were going to be the last frame on