MIPS: Fix for Ins macro-assembler instruction for non-mips32r2 platforms.

BUG=
TEST=

Review URL: http://codereview.chromium.org/8520023
Patch from Gergely Kis <gergely@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10015 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/macro-assembler-mips.cc

@@ -910,34 +910,21 @@ void MacroAssembler::Ins(Register rt,
                          uint16_t pos,
                          uint16_t size) {
   ASSERT(pos < 32);
-  ASSERT(pos + size < 32);
+  ASSERT(pos + size <= 32);
+  ASSERT(size != 0);
 
   if (mips32r2) {
     ins_(rt, rs, pos, size);
   } else {
     ASSERT(!rt.is(t8) && !rs.is(t8));
-
-    srl(t8, rt, pos + size);
-    // The left chunk from rt that needs to
-    // be saved is on the right side of t8.
-    sll(at, t8, pos + size);
-    // The 'at' register now contains the left chunk on
-    // the left (proper position) and zeroes.
-    sll(t8, rt, 32 - pos);
-    // t8 now contains the right chunk on the left and zeroes.
-    srl(t8, t8, 32 - pos);
-    // t8 now contains the right chunk on
-    // the right (proper position) and zeroes.
-    or_(rt, at, t8);
-    // rt now contains the left and right chunks from the original rt
-    // in their proper position and zeroes in the middle.
-    sll(t8, rs, 32 - size);
-    // t8 now contains the chunk from rs on the left and zeroes.
-    srl(t8, t8, 32 - size - pos);
-    // t8 now contains the original chunk from rs in
-    // the middle (proper position).
-    or_(rt, rt, t8);
-    // rt now contains the result of the ins instruction in R2 mode.
+    Subu(at, zero_reg, Operand(1));
+    srl(at, at, 32 - size);
+    and_(t8, rs, at);
+    sll(t8, t8, pos);
+    sll(at, at, pos);
+    nor(at, at, zero_reg);
+    and_(at, rt, at);
+    or_(rt, t8, at);
   }
 }