From: Aleksey Demakov <ademakov@gmail.com>
Date: Thu, 6 Jul 2006 12:04:07 +0000 (+0000)
Subject: fix division by power of two
X-Git-Tag: before.move.to.git~224
X-Git-Url: https://git.unchartedbackwaters.co.uk/w/?a=commitdiff_plain;h=5a5513281fe61003415c09a56df13c37b16cfc6e;p=francis%2Flibjit.git

fix division by power of two
---

diff --git a/ChangeLog b/ChangeLog
index 78bcf61..0792140 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2006-07-06  Aleksey Demakov  <ademakov@gmail.com>
+
+	* jit/jit-rules-x86.ins: fix division by power of two.
+
 2006-07-05  Aleksey Demakov  <ademakov@gmail.com>
 
 	* configure.in: make new register allocator the default.
diff --git a/jit/jit-rules-x86.ins b/jit/jit-rules-x86.ins
index d6d73cb..81838be 100644
--- a/jit/jit-rules-x86.ins
+++ b/jit/jit-rules-x86.ins
@@ -554,8 +554,8 @@ JIT_OP_IDIV: more_space
 	}
 	[reg, imm, if("(((jit_nuint)$2) & (((jit_nuint)$2) - 1)) == 0")] -> {
 		/* x & (x - 1) is equal to zero if x is a power of 2  */
-		jit_nuint shift, value;
-		for(shift = 0, value = $2; value; value >>= 1)
+		jit_nuint shift, value = $2 >> 1;
+		for(shift = 0; value; value >>= 1)
 		{
 		    ++shift;
 		}
@@ -594,12 +594,12 @@ JIT_OP_IDIV_UN: more_space
 	}
 	[reg, imm, if("(((jit_nuint)$2) & (((jit_nuint)$2) - 1)) == 0")] -> {
 		/* x & (x - 1) is equal to zero if x is a power of 2  */
-		jit_nuint shift, value;
-		for(shift = 0, value = $2; value; value >>= 1)
+		jit_nuint shift, value = $2 >> 1;
+		for(shift = 0; value; value >>= 1)
 		{
 		    ++shift;
 		}
-		x86_shift_reg_imm(inst, X86_SAR, $1, shift);
+		x86_shift_reg_imm(inst, X86_SHR, $1, shift);
 	}
 	[reg("eax"), imm, scratch("?", "edx")] -> {
 		x86_mov_reg_imm(inst, $3, $2);