4 files changed, 31 insertions, 2 deletions

diff --git a/src/lj_asm.c b/src/lj_asm.c
index c7365404..038f4d1c 100644
--- a/src/lj_asm.c
+++ b/src/lj_asm.c
@@ -30,6 +30,10 @@
 #include "lj_vm.h"
 #include "lj_target.h"
 
+#ifdef LUA_USE_ASSERT
+#include <stdio.h>
+#endif
+
 /* -- Assembler state and common macros ----------------------------------- */
 
 /* Assembler state. */
@@ -38,6 +42,9 @@ typedef struct ASMState {
 
   MCode *mcp;           /* Current MCode pointer (grows down). */
   MCode *mclim;         /* Lower limit for MCode memory + red zone. */
+#ifdef LUA_USE_ASSERT
+  MCode *mcp_prev;      /* Red zone overflow check. */
+#endif
 
   IRIns *ir;            /* Copy of pointer to IR instructions/constants. */
   jit_State *J;         /* JIT compiler state. */
@@ -110,14 +117,28 @@ typedef struct ASMState {
 
 /* Sparse limit checks using a red zone before the actual limit. */
 #define MCLIM_REDZONE   64
-#define checkmclim(as) \
-  if (LJ_UNLIKELY(as->mcp < as->mclim)) asm_mclimit(as)
 
 static LJ_NORET LJ_NOINLINE void asm_mclimit(ASMState *as)
 {
   lj_mcode_limiterr(as->J, (size_t)(as->mctop - as->mcp + 4*MCLIM_REDZONE));
 }
 
+static LJ_AINLINE void checkmclim(ASMState *as)
+{
+#ifdef LUA_USE_ASSERT
+  if (as->mcp + MCLIM_REDZONE < as->mcp_prev) {
+    IRIns *ir = IR(as->curins+1);
+    fprintf(stderr, "RED ZONE OVERFLOW: %p IR %04d  %02d %04d %04d\n", as->mcp,
+            as->curins+1-REF_BIAS, ir->o, ir->op1-REF_BIAS, ir->op2-REF_BIAS);
+    lua_assert(0);
+  }
+#endif
+  if (LJ_UNLIKELY(as->mcp < as->mclim)) asm_mclimit(as);
+#ifdef LUA_USE_ASSERT
+  as->mcp_prev = as->mcp;
+#endif
+}
+
 #ifdef RID_NUM_KREF
 #define ra_iskref(ref)          ((ref) < RID_NUM_KREF)
 #define ra_krefreg(ref)         ((Reg)(RID_MIN_KREF + (Reg)(ref)))
@@ -1181,6 +1202,7 @@ static void asm_phi_copyspill(ASMState *as)
         if (ra_hasspill(irl->s) && !irt_isfp(ir->t)) {
           emit_spstore(as, irl, r, sps_scale(irl->s));
           emit_spload(as, ir, r, sps_scale(ir->s));
+          checkmclim(as);
         }
       }
     }
@@ -1206,6 +1228,7 @@ static void asm_phi_copyspill(ASMState *as)
         if (ra_hasspill(irl->s) && irt_isfp(ir->t)) {
           emit_spstore(as, irl, r, sps_scale(irl->s));
           emit_spload(as, ir, r, sps_scale(ir->s));
+          checkmclim(as);
         }
       }
     }
@@ -1822,6 +1845,9 @@ void lj_asm_trace(jit_State *J, GCtrace *T)
 
   do {
     as->mcp = as->mctop;
+#ifdef LUA_USE_ASSERT
+    as->mcp_prev = as->mcp;
+#endif
     as->curins = T->nins;
     RA_DBG_START();
     RA_DBGX((as, "===== STOP ====="));
diff --git a/src/lj_asm_mips.h b/src/lj_asm_mips.h
index e80f7582..7d1a8c68 100644
--- a/src/lj_asm_mips.h
+++ b/src/lj_asm_mips.h
@@ -283,6 +283,7 @@ static void asm_gencall(ASMState *as, const CCallInfo *ci, IRRef *args)
       else
         ofs += 4;
     }
+    checkmclim(as);
   }
 }
 
diff --git a/src/lj_asm_ppc.h b/src/lj_asm_ppc.h
index 7637f6a6..34bd721f 100644
--- a/src/lj_asm_ppc.h
+++ b/src/lj_asm_ppc.h
@@ -286,6 +286,7 @@ static void asm_gencall(ASMState *as, const CCallInfo *ci, IRRef *args)
       else
         ofs += 4;
     }
+    checkmclim(as);
   }
   if ((ci->flags & CCI_VARARG))  /* Vararg calls need to know about FPR use. */
     emit_tab(as, fpr == REGARG_FIRSTFPR ? PPCI_CRXOR : PPCI_CREQV, 6, 6, 6);
diff --git a/src/lj_asm_x86.h b/src/lj_asm_x86.h
index 28aa2791..8bae1789 100644
--- a/src/lj_asm_x86.h
+++ b/src/lj_asm_x86.h
@@ -512,6 +512,7 @@ static void asm_gencall(ASMState *as, const CCallInfo *ci, IRRef *args)
       }
       ofs += sizeof(intptr_t);
     }
+    checkmclim(as);
   }
 #if LJ_64 && !LJ_ABI_WIN
   if (patchnfpr) *patchnfpr = fpr - REGARG_FIRSTFPR;