# HG changeset patch
# User twisti
# Date 1389326695 28800
# Node ID 7737fbb055b0923288a47e8bfe0cc4f9c908fd2e
# Parent  f4f0a8a01ce0b4e8bcb4fa2c3fa7618af0a9fcc7
check branch displacement when patching short branches

diff -r f4f0a8a01ce0 -r 7737fbb055b0 graal/com.oracle.graal.asm.amd64/src/com/oracle/graal/asm/amd64/AMD64Assembler.java
--- a/graal/com.oracle.graal.asm.amd64/src/com/oracle/graal/asm/amd64/AMD64Assembler.java	Thu Jan 09 16:18:29 2014 +0100
+++ b/graal/com.oracle.graal.asm.amd64/src/com/oracle/graal/asm/amd64/AMD64Assembler.java	Thu Jan 09 20:04:55 2014 -0800
@@ -2437,7 +2437,14 @@
         } else if (op == 0xEB || (op & 0xF0) == 0x70) {
 
             // short offset operators (jmp and jcc)
-            int imm8 = branchTarget - (branch + 2);
+            final int imm8 = branchTarget - (branch + 2);
+            /*
+             * Since a wrongly patched short branch can potentially lead to working but really bad
+             * behaving code we should always fail with an exception instead of having an assert.
+             */
+            if (!NumUtil.isByte(imm8)) {
+                throw new InternalError("branch displacement out of range: " + imm8);
+            }
             codeBuffer.emitByte(imm8, branch + 1);
 
         } else {