# HG changeset patch
# User fyang
# Date 1527117610 -28800
# Node ID 9a87afc491488c9a3a1b74d36124d769808bd8a4
# Parent  b4bfc263cdc625f1dd509cf1423fb3b56a184e18
8203041: AArch64: fix overflow in immediate cmp/cmn instruction
Summary: fix overflow in immediate cmp/cmn instruction for AArch64
Reviewed-by: aph, dpochepk, drwhite
Contributed-by: joshua.zhu@arm.com

diff -r b4bfc263cdc6 -r 9a87afc49148 src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp
--- a/src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp	Wed May 23 21:08:33 2018 +0200
+++ b/src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp	Thu May 24 07:20:10 2018 +0800
@@ -3851,7 +3851,9 @@
     __ sub(cnt1, cnt1, 8 * wordSize);
     __ eor(tmp7, tmp7, tmp8);
     __ ldp(tmp2, tmp4, Address(__ post(a2, 2 * wordSize)));
-    __ cmp(cnt1, loopThreshold);
+    // tmp6 is not used. MacroAssembler::subs is used here (rather than
+    // cmp) because subs allows an unlimited range of immediate operand.
+    __ subs(tmp6, cnt1, loopThreshold);
     __ orr(tmp5, tmp5, tmp7);
     __ cbnz(tmp5, NOT_EQUAL);
     __ br(__ GE, LOOP);
@@ -3877,7 +3879,7 @@
     __ ld1(v0, v1, v2, v3, __ T2D, Address(__ post(a1, 4 * 2 * wordSize)));
     __ sub(cnt1, cnt1, 8 * wordSize);
     __ ld1(v4, v5, v6, v7, __ T2D, Address(__ post(a2, 4 * 2 * wordSize)));
-    __ cmp(cnt1, loopThreshold);
+    __ subs(tmp1, cnt1, loopThreshold);
     __ eor(v0, __ T16B, v0, v4);
     __ eor(v1, __ T16B, v1, v5);
     __ eor(v2, __ T16B, v2, v6);
@@ -3936,7 +3938,7 @@
     }
     if (UseSIMDForArrayEquals) {
       if (SoftwarePrefetchHintDistance >= 0) {
-        __ cmp(cnt1, prefetchLoopThreshold);
+        __ subs(tmp1, cnt1, prefetchLoopThreshold);
         __ br(__ LE, NO_PREFETCH_LARGE_LOOP);
         generate_large_array_equals_loop_simd(prefetchLoopThreshold,
             /* prfm = */ true, NOT_EQUAL);
@@ -3949,7 +3951,7 @@
     } else {
       __ push(spilled_regs, sp);
       if (SoftwarePrefetchHintDistance >= 0) {
-        __ cmp(cnt1, prefetchLoopThreshold);
+        __ subs(tmp1, cnt1, prefetchLoopThreshold);
         __ br(__ LE, NO_PREFETCH_LARGE_LOOP);
         generate_large_array_equals_loop_nonsimd(prefetchLoopThreshold,
             /* prfm = */ true, NOT_EQUAL);