From 4c74f704644c2f843cb304aba0c901723097ff14 Mon Sep 17 00:00:00 2001
From: Mike Pall <mike>
Date: Sun, 6 Feb 2011 00:45:39 +0100
Subject: Strength-reduce 32 to 64 bit widening for XLOAD U8/U16 inputs.

---
 src/lj_opt_fold.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/lj_opt_fold.c b/src/lj_opt_fold.c
index 1172f4fc..f4872046 100644
--- a/src/lj_opt_fold.c
+++ b/src/lj_opt_fold.c
@@ -917,6 +917,8 @@ LJFOLDF(simplify_conv_sext)
   if (!(fins->op2 & IRCONV_SEXT))
     return NEXTFOLD;
   PHIBARRIER(fleft);
+  if (fleft->o == IR_XLOAD && (irt_isu8(fleft->t) || irt_isu16(fleft->t)))
+    goto ok_reduce;
   if (fleft->o == IR_ADD && irref_isk(fleft->op2)) {
     ofs = (int64_t)IR(fleft->op2)->i;
     ref = fleft->op1;
@@ -926,6 +928,7 @@ LJFOLDF(simplify_conv_sext)
     IRRef lo = J->scev.dir ? J->scev.start : J->scev.stop;
     lua_assert(irt_isint(J->scev.t));
     if (lo && IR(lo)->i + ofs >= 0) {
+    ok_reduce:
 #if LJ_TARGET_X64
       /* Eliminate widening. All 32 bit ops do an implicit zero-extension. */
       return LEFTFOLD;
-- 
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