From: Florian Krohm <flo2030@eich-krohm.de>
Date: Tue, 19 Aug 2025 21:11:25 +0000 (+0000)
Subject: s390: Fix code generation for Iop_MullS8/16 and Iop_MullU8/16
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7c63587b7f6a2cdbd073d92c0a45f197ed993e0a;p=thirdparty%2Fvalgrind.git

s390: Fix code generation for Iop_MullS8/16 and Iop_MullU8/16

Multiplication is performed using 4-byte values.
There were two bugs:
(1) Iop_MullS8/16 operands weren't sign-extended
(2) No shifting and OR'ing required to access the result. r11[32:63] has it.

Found by iropt-test.
---

diff --git a/VEX/priv/host_s390_isel.c b/VEX/priv/host_s390_isel.c
index 2b075c930..ecce74d78 100644
--- a/VEX/priv/host_s390_isel.c
+++ b/VEX/priv/host_s390_isel.c
@@ -1254,7 +1254,17 @@ s390_isel_int_expr_wrk(ISelEnv *env, IRExpr *expr)
          goto do_multiply;
 
       case Iop_MullS8:
+         arg1 = IRExpr_Unop(Iop_8Sto32, arg1);
+         arg2 = IRExpr_Unop(Iop_8Sto32, arg2);
+         is_signed_multiply = True;
+         goto do_multiply;
+
       case Iop_MullS16:
+         arg1 = IRExpr_Unop(Iop_16Sto32, arg1);
+         arg2 = IRExpr_Unop(Iop_16Sto32, arg2);
+         is_signed_multiply = True;
+         goto do_multiply;
+
       case Iop_MullS32:
          is_signed_multiply = True;
          goto do_multiply;
@@ -1278,9 +1288,16 @@ s390_isel_int_expr_wrk(ISelEnv *env, IRExpr *expr)
             /* Multiply */
             addInstr(env, s390_insn_mul(arg_size, r10, r11, op2, is_signed_multiply));
 
+            res  = newVRegI(env);
+            if (arg_size == 1 || arg_size == 2) {
+               /* For 8-bit and 16-bit multiplication the result is in
+                  r11[32:63] */
+               addInstr(env, s390_insn_move(size, res, r11));
+               return res;
+            }
+
             /* The result is in registers r10 and r11. Combine them into a SIZE-bit
                value into the destination register. */
-            res  = newVRegI(env);
             addInstr(env, s390_insn_move(arg_size, res, r10));
             value = s390_opnd_imm(arg_size * 8);
             addInstr(env, s390_insn_alu(size, S390_ALU_LSH, res, value));