From: Florian Krohm <flo2030@eich-krohm.de>
Date: Tue, 12 Aug 2025 21:52:18 +0000 (+0000)
Subject: New command line flag --vex-iropt-fold-expr
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=679e7bced9;p=thirdparty%2Fvalgrind.git

New command line flag --vex-iropt-fold-expr

Defaults to "yes".
Add VexControl::iropt_fold_expr and observe it in fold_Expr_WRK.

This flag will be used shortly in the iropt-test program.
Users are not expected to use it which is why I'm not announcing
it in NEWS.
---

diff --git a/VEX/priv/ir_opt.c b/VEX/priv/ir_opt.c
index ebea8ba0e..fa2877f6b 100644
--- a/VEX/priv/ir_opt.c
+++ b/VEX/priv/ir_opt.c
@@ -1462,6 +1462,8 @@ static IRExpr* chase1 ( IRExpr** env, IRExpr* e )
 __attribute__((noinline))
 static IRExpr* fold_Expr_WRK ( IRExpr** env, IRExpr* e )
 {
+   if (UNLIKELY(vex_control.iropt_fold_expr == False)) return e;
+
    Int     shift;
    IRExpr* e2 = e; /* e2 is the result of folding e, if possible */
 
diff --git a/VEX/priv/main_globals.c b/VEX/priv/main_globals.c
index 9167e8131..c0536bea7 100644
--- a/VEX/priv/main_globals.c
+++ b/VEX/priv/main_globals.c
@@ -57,7 +57,7 @@ Int vex_debuglevel = 0;
 Int vex_traceflags = 0;
 
 /* Max # guest insns per bb */
-VexControl vex_control = { 0,0,VexRegUpd_INVALID,0,0,False,0 };
+VexControl vex_control = { 0,0,VexRegUpd_INVALID,0,0,False,0,False };
 
 
 
diff --git a/VEX/priv/main_main.c b/VEX/priv/main_main.c
index 619cace2e..3e64ad7de 100644
--- a/VEX/priv/main_main.c
+++ b/VEX/priv/main_main.c
@@ -204,6 +204,7 @@ void LibVEX_default_VexControl ( /*OUT*/ VexControl* vcon )
    vcon->guest_max_insns                = 60;
    vcon->guest_chase                    = True;
    vcon->regalloc_version               = 3;
+   vcon->iropt_fold_expr                = True;
 }
 
 void LibVEX_set_VexControl ( VexControl vcon )
diff --git a/VEX/pub/libvex.h b/VEX/pub/libvex.h
index 177969978..da295f85f 100644
--- a/VEX/pub/libvex.h
+++ b/VEX/pub/libvex.h
@@ -572,6 +572,9 @@ typedef
          - '3': current, faster implementation; perhaps producing slightly worse
                 spilling decisions. */
       UInt regalloc_version;
+      /* When false constant folding and algebric simplification is disabled.
+         This is used in the iropt tester. */
+      Bool iropt_fold_expr;
    }
    VexControl;
 
diff --git a/coregrind/m_main.c b/coregrind/m_main.c
index c94e5e053..87c75d2ac 100644
--- a/coregrind/m_main.c
+++ b/coregrind/m_main.c
@@ -294,6 +294,7 @@ static void usage_NORETURN ( int need_help )
 "    --vex-iropt-verbosity=<0..9>           [0]\n"
 "    --vex-iropt-level=<0..2>               [2]\n"
 "    --vex-iropt-unroll-thresh=<0..400>     [120]\n"
+"    --vex-iropt-fold-expr=no|yes           [yes]\n"
 "    --vex-guest-max-insns=<1..100>         [50]\n"
 "    --vex-guest-chase=no|yes               [yes]\n"
 "    Precise exception control.  Possible values for 'mode' are as follows\n"
@@ -761,6 +762,8 @@ static void process_option (Clo_Mode mode,
                        VG_(clo_vex_control).iropt_level, 0, 2) {}
    else if VG_BINT_CLO(arg, "--vex-regalloc-version",
                        VG_(clo_vex_control).regalloc_version, 2, 3) {}
+   else if VG_BOOL_CLOM(cloPD, arg, "--vex-iropt-fold-expr",
+                        VG_(clo_vex_control).iropt_fold_expr) {}
 
    else if (VG_STRINDEX_CLO(arg, "--vex-iropt-register-updates",
                            pxStrings, ix)