fail with GraalError if jmpb used with offset that cannot be encoded …

…into a byte
jonezineworks · Apr 12, 2019 · 8eb34f4 · 8eb34f4
1 parent 1fa8eff
commit 8eb34f4
Showing 1 changed file with 5 additions and 8 deletions.
diff --git a/...src/org.graalvm.compiler.asm.amd64/src/org/graalvm/compiler/asm/amd64/AMD64Assembler.java b/...src/org.graalvm.compiler.asm.amd64/src/org/graalvm/compiler/asm/amd64/AMD64Assembler.java
@@ -75,7 +75,6 @@
 import org.graalvm.compiler.asm.Label;
 import org.graalvm.compiler.asm.amd64.AMD64Address.Scale;
 import org.graalvm.compiler.asm.amd64.AVXKind.AVXSize;
-import org.graalvm.compiler.core.common.NumUtil;
 import org.graalvm.compiler.core.common.calc.Condition;
 import org.graalvm.compiler.debug.GraalError;
 
@@ -1950,11 +1949,11 @@ public final void jmp(AMD64Address adr) {
     public final void jmpb(Label l) {
         if (l.isBound()) {
             int shortSize = 2;
-            int entry = l.position();
-            assert isByte((entry - position()) + shortSize) : "Dispacement too large for a short jmp";
-            long offs = entry - position();
+            // Displacement is relative to byte just after jmpb instruction
+            int displacement = l.position() - position() - shortSize;
+            GraalError.guarantee(isByte(displacement), "Displacement too large to be encoded as a byte: %d", displacement);
             emitByte(0xEB);
-            emitByte((int) ((offs - shortSize) & 0xFF));
+            emitByte(displacement & 0xFF);
         } else {
             l.addPatchAt(position(), this);
             emitByte(0xEB);
@@ -3396,9 +3395,7 @@ protected final void patchJumpTarget(int branch, int branchTarget) {
              * 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("Displacement too large to be encoded as a byte: " + imm8);
-            }
+            GraalError.guarantee(isByte(imm8), "Displacement too large to be encoded as a byte: %d", imm8);
             emitByte(imm8, branch + 1);
 
         } else {