From: Mike Pall <mike>
Date: Wed, 22 Jun 2011 18:38:07 +0000 (+0200)
Subject: x86/x64: Fix register allocation for variable shifts.
X-Git-Tag: v2.0.0-beta8~5
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d4da9ff55ef01019c55246cd41ccd7510505cfe1;p=thirdparty%2FLuaJIT.git

x86/x64: Fix register allocation for variable shifts.
---

diff --git a/src/lj_asm_x86.h b/src/lj_asm_x86.h
index ba28792d..da818c68 100644
--- a/src/lj_asm_x86.h
+++ b/src/lj_asm_x86.h
@@ -1878,15 +1878,17 @@ static void asm_bitshift(ASMState *as, IRIns *ir, x86Shift xs)
     default: emit_shifti(as, REX_64IR(ir, xs), dest, shift); break;
     }
   } else {  /* Variable shifts implicitly use register cl (i.e. ecx). */
-    RegSet allow = rset_exclude(RSET_GPR, RID_ECX);
-    Reg right = irr->r;
-    if (ra_noreg(right)) {
+    Reg right;
+    dest = ra_dest(as, ir, rset_exclude(RSET_GPR, RID_ECX));
+    if (dest == RID_ECX) {
+      dest = ra_scratch(as, rset_exclude(RSET_GPR, RID_ECX));
+      emit_rr(as, XO_MOV, RID_ECX, dest);
+    }
+    right = irr->r;
+    if (ra_noreg(right))
       right = ra_allocref(as, rref, RID2RSET(RID_ECX));
-    } else if (right != RID_ECX) {
-      rset_clear(allow, right);
+    else if (right != RID_ECX)
       ra_scratch(as, RID2RSET(RID_ECX));
-    }
-    dest = ra_dest(as, ir, allow);
     emit_rr(as, XO_SHIFTcl, REX_64IR(ir, xs), dest);
     if (right != RID_ECX) {
       ra_noweak(as, right);