fix(modexp): add debuged failing ref test

arithmetization/src/main/java/net/consensys/linea/zktracer/module/hub/precompiles/ModexpMetadata.java

@@ -122,7 +122,7 @@ public EWord rawLeadingWord() {
   }
 
   public boolean extractModulus() {
-    return (callData.size() > MBS_MIN_OFFSET + bbsInt() + ebsInt()) && !mbs().isZero();
+    return (callData.size() > BASE_MIN_OFFSET + bbsInt() + ebsInt()) && !mbs().isZero();
   }
 
   public boolean extractBase() {

arithmetization/src/main/java/net/consensys/linea/zktracer/module/mmu/instructions/ModexpData.java

@@ -20,6 +20,7 @@
 import static net.consensys.linea.zktracer.module.constants.GlobalConstants.MMIO_INST_RAM_TO_LIMB_ONE_SOURCE;
 import static net.consensys.linea.zktracer.module.constants.GlobalConstants.MMIO_INST_RAM_TO_LIMB_TRANSPLANT;
 import static net.consensys.linea.zktracer.module.constants.GlobalConstants.MMIO_INST_RAM_TO_LIMB_TWO_SOURCE;
+import static net.consensys.linea.zktracer.module.mmu.Trace.NB_MICRO_ROWS_TOT_MODEXP_DATA;
 import static net.consensys.linea.zktracer.types.Conversions.longToBytes;
 
 import java.util.ArrayList;
@@ -138,10 +139,10 @@ private void row2() {
     wcpCallRecords.add(
         MmuWcpCallRecord.instLtBuilder().arg1Lo(wcpArg1).arg2Lo(wcpArg2).result(wcpResult).build());
 
-    EucOperation eucOp = euc.callEUC(longToBytes(numberRightPaddingBytes), Bytes.of(LLARGE));
+    final EucOperation eucOp = euc.callEUC(longToBytes(numberRightPaddingBytes), Bytes.of(LLARGE));
     initialTotalRightZeroes = eucOp.quotient().toInt();
     initialTotalNonTrivial =
-        Trace.NB_MICRO_ROWS_TOT_MODEXP_DATA - initialTotalLeftZeroes - initialTotalRightZeroes;
+        NB_MICRO_ROWS_TOT_MODEXP_DATA - initialTotalLeftZeroes - initialTotalRightZeroes;
     rightPaddingRemainder = eucOp.remainder().toInt();
     eucCallRecords.add(
         MmuEucCallRecord.builder()
@@ -156,9 +157,13 @@ private void row3() {
     // row n°3
     final Bytes wcpArg1 = longToBytes(initialTotalNonTrivial);
     final Bytes wcpArg2 = Bytes.of(1);
-    final boolean wcpResult = wcp.callEQ(wcpArg1, wcpArg2);
+    final boolean singleNonTrivialMmioOperation = wcp.callEQ(wcpArg1, wcpArg2);
     wcpCallRecords.add(
-        MmuWcpCallRecord.instEqBuilder().arg1Lo(wcpArg1).arg2Lo(wcpArg2).result(wcpResult).build());
+        MmuWcpCallRecord.instEqBuilder()
+            .arg1Lo(wcpArg1)
+            .arg2Lo(wcpArg2)
+            .result(singleNonTrivialMmioOperation)
+            .build());
 
     final long dividend = parameterOffset;
     final EucOperation eucOp = euc.callEUC(longToBytes(dividend), Bytes.of(LLARGE));
@@ -171,7 +176,7 @@ private void row3() {
             .quotient(eucOp.quotient().toLong())
             .remainder((short) eucOp.remainder().toInt())
             .build());
-    if (wcpResult) {
+    if (singleNonTrivialMmioOperation) {
       firstLimbByteSize = (short) (dataRunsOut ? leftoverDataSize : parameterByteSize);
     } else {
       firstLimbByteSize = (short) (LLARGE - initialTargetByteOffset);

arithmetization/src/main/java/net/consensys/linea/zktracer/module/oob/OobOperation.java

@@ -32,6 +32,7 @@
 import static net.consensys.linea.zktracer.module.constants.GlobalConstants.GAS_CONST_G_CALL_STIPEND;
 import static net.consensys.linea.zktracer.module.constants.GlobalConstants.MAX_CODE_SIZE;
 import static net.consensys.linea.zktracer.module.hub.fragment.imc.oob.OobInstruction.*;
+import static net.consensys.linea.zktracer.module.hub.precompiles.ModexpMetadata.BASE_MIN_OFFSET;
 import static net.consensys.linea.zktracer.module.oob.Trace.CT_MAX_BLAKE2F_CDS;
 import static net.consensys.linea.zktracer.module.oob.Trace.CT_MAX_BLAKE2F_PARAMS;
 import static net.consensys.linea.zktracer.module.oob.Trace.CT_MAX_CALL;
@@ -1138,7 +1139,7 @@ private void setModexpExtract(ModexpExtractOobCall prcModexpExtractOobCall) {
         callToLT(
             3,
             BigInteger.ZERO,
-            BigInteger.valueOf(96)
+            BigInteger.valueOf(BASE_MIN_OFFSET)
                 .add(prcModexpExtractOobCall.getBbs().add(prcModexpExtractOobCall.getEbs())),
             BigInteger.ZERO,
             prcModexpExtractOobCall.getCds());

arithmetization/src/test/java/net/consensys/linea/zktracer/precompiles/ModexpTests.java

@@ -26,6 +26,7 @@
 import net.consensys.linea.testing.BytecodeRunner;
 import net.consensys.linea.zktracer.opcode.OpCode;
 import org.apache.tuweni.bytes.Bytes;
+import org.apache.tuweni.bytes.Bytes32;
 import org.hyperledger.besu.datatypes.Address;
 import org.junit.jupiter.api.Test;
 
@@ -236,4 +237,39 @@ void appendAllZeroCallDataModexpCalls(BytecodeCompiler program, int callDataSize
         .op(OpCode.STATICCALL)
         .op(OpCode.POP);
   }
+
+  @Test
+  // We trigger a ModexpData MMU Call where the sourceOffset = referenceSize for the MmuCall
+  void referenceSizeEqualsSourceOffset() {
+    final Bytes bytecode =
+        BytecodeCompiler.newProgram()
+            // bbs = 2
+            .push(Bytes32.leftPad(Bytes.of(2)))
+            .push(0) // offset
+            .op(OpCode.MSTORE)
+            // ebs = 3
+            .push(Bytes32.leftPad(Bytes.of(3)))
+            .push(32) // offset
+            .op(OpCode.MSTORE)
+            // mbs = 4
+            .push(Bytes32.leftPad(Bytes.of(4)))
+            .push(64) // offset
+            .op(OpCode.MSTORE)
+            // MSTORE ebm
+            .push(Bytes32.rightPad(Bytes.fromHexString("0xba7e000ec70000080d")))
+            .push(96)
+            .op(OpCode.MSTORE)
+            // Call Modexp
+            .push(0) // returnSize
+            .push(0) // returnOffset
+            .push(98) // cds = 96 + bbs => trigger a MMU Call where the sourceOffset = referenceSize
+            .push(0) // cdo
+            .push(0) // value
+            .push(Address.MODEXP) // address
+            .push(0xffff) // gas
+            .op(OpCode.CALL)
+            .op(OpCode.POP)
+            .compile();
+    BytecodeRunner.of(bytecode).run();
+  }
 }