# HG changeset patch
# User aph
# Date 1469203508 -3600
# Node ID 00aba4bf1a8308ac2267665fd7b0a5f50abc10ca
# Parent  40d48ddc12bcf57f6de818cc9219f8aa85472f8c
8161190: AArch64: Fix overflow in immediate cmp instruction
Summary: Use subs instead of cmp to compare BlockZeroingLowLimit. Subs can check and handle immediate out of range correctly.
Reviewed-by: aph
Contributed-by: yang.zhang@linaro.org

diff -r 40d48ddc12bc -r 00aba4bf1a83 hotspot/src/cpu/aarch64/vm/macroAssembler_aarch64.cpp
--- a/hotspot/src/cpu/aarch64/vm/macroAssembler_aarch64.cpp	Wed Jul 20 19:35:08 2016 +0300
+++ b/hotspot/src/cpu/aarch64/vm/macroAssembler_aarch64.cpp	Fri Jul 22 17:05:08 2016 +0100
@@ -4916,7 +4916,7 @@
   // alignment.
   if (!is_large || !(BlockZeroingLowLimit >= zva_length * 2)) {
     int low_limit = MAX2(zva_length * 2, (int)BlockZeroingLowLimit);
-    cmp(cnt, low_limit >> 3);
+    subs(tmp, cnt, low_limit >> 3);
     br(Assembler::LT, small);
   }
 
diff -r 40d48ddc12bc -r 00aba4bf1a83 hotspot/src/cpu/aarch64/vm/stubGenerator_aarch64.cpp
--- a/hotspot/src/cpu/aarch64/vm/stubGenerator_aarch64.cpp	Wed Jul 20 19:35:08 2016 +0300
+++ b/hotspot/src/cpu/aarch64/vm/stubGenerator_aarch64.cpp	Fri Jul 22 17:05:08 2016 +0100
@@ -2346,8 +2346,9 @@
     __ subw(count, count, cnt_words, Assembler::LSL, 3 - shift);
     if (UseBlockZeroing) {
       Label non_block_zeroing, rest;
+      Register tmp = rscratch1;
       // count >= BlockZeroingLowLimit && value == 0
-      __ cmp(cnt_words, BlockZeroingLowLimit >> 3);
+      __ subs(tmp, cnt_words, BlockZeroingLowLimit >> 3);
       __ ccmp(value, 0 /* comparing value */, 0 /* NZCV */, Assembler::GE);
       __ br(Assembler::NE, non_block_zeroing);
       __ mov(bz_base, to);