From: Ivo Raisr <ivosh@ivosh.net>
Date: Sat, 16 Sep 2017 16:48:36 +0000 (+0200)
Subject: Fix a typo bug in VEX register allocator v3.
X-Git-Tag: VALGRIND_3_14_0~258
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b9df4c8dec4d3154257818eb81111df43f2a7bf2;p=thirdparty%2Fvalgrind.git

Fix a typo bug in VEX register allocator v3.

Also scanning a few more instructions ahead helps producing
better code.
---

diff --git a/VEX/priv/host_generic_reg_alloc3.c b/VEX/priv/host_generic_reg_alloc3.c
index 8ee4e482b8..5b2a9f2fa0 100644
--- a/VEX/priv/host_generic_reg_alloc3.c
+++ b/VEX/priv/host_generic_reg_alloc3.c
@@ -323,7 +323,7 @@ static inline HReg find_vreg_to_spill(
       - reg_usage[scan_forward_from]
       - reg_usage[scan_forward_end], where scan_forward_end
            = MIN(scan_forward_max, scan_forward_from + FEW_INSTRUCTIONS). */
-#  define FEW_INSTRUCTIONS 5
+#  define FEW_INSTRUCTIONS 20
    UInt scan_forward_end
       = (scan_forward_max <= scan_forward_from + FEW_INSTRUCTIONS) ?
         scan_forward_max : scan_forward_from + FEW_INSTRUCTIONS;
@@ -344,10 +344,10 @@ static inline HReg find_vreg_to_spill(
                }
             }
 
-            if (ii - scan_forward_from > distance_so_far) {
-               distance_so_far = ii = scan_forward_from;
+            if (ii >= distance_so_far) {
+               distance_so_far = ii;
                vreg_found = vreg;
-               if (ii + distance_so_far == scan_forward_end) {
+               if (distance_so_far == scan_forward_end) {
                   break; /* We are at the end. Nothing could be better. */
                }
             }