tcg/optimize: Fix TCG_COND_TST* simplification of setcond2

Argument ordering for setcond2 is:

  output, a_low, a_high, b_low, b_high, cond

The test is supposed to be against b_low, not a_high.

Cc: qemu-stable@nongnu.org
Fixes: ceb9ee06b7 ("tcg/optimize: Handle TCG_COND_TST{EQ,NE}")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2413
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240701024623.1265028-1-richard.henderson@linaro.org>
(cherry picked from commit a71d9dfbf6)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

tcg/optimize.c

@@ -2274,7 +2274,7 @@ static bool fold_setcond2(OptContext *ctx, TCGOp *op)
 
     case TCG_COND_TSTEQ:
     case TCG_COND_TSTNE:
-        if (arg_is_const_val(op->args[2], 0)) {
+        if (arg_is_const_val(op->args[3], 0)) {
             goto do_setcond_high;
         }
         if (arg_is_const_val(op->args[4], 0)) {

tests/tcg/x86_64/Makefile.target

@@ -8,6 +8,8 @@
 
 include $(SRC_PATH)/tests/tcg/i386/Makefile.target
 
+X86_64_TESTS += test-2413
+
 ifeq ($(filter %-linux-user, $(TARGET)),$(TARGET))
 X86_64_TESTS += vsyscall
 X86_64_TESTS += noexec

tests/tcg/x86_64/test-2413.c

@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright 2024 Linaro, Ltd. */
+/* See https://gitlab.com/qemu-project/qemu/-/issues/2413 */
+
+#include <assert.h>
+
+void test(unsigned long *a, unsigned long *d, unsigned long c)
+{
+    asm("xorl %%eax, %%eax\n\t"
+        "xorl %%edx, %%edx\n\t"
+        "testb $0x20, %%cl\n\t"
+        "sete %%al\n\t"
+        "setne %%dl\n\t"
+        "shll %%cl, %%eax\n\t"
+        "shll %%cl, %%edx\n\t"
+        : "=a"(*a), "=d"(*d)
+        : "c"(c));
+}
+
+int main(void)
+{
+    unsigned long a, c, d;
+
+    for (c = 0; c < 64; c++) {
+        test(&a, &d, c);
+        assert(a == (c & 0x20 ? 0 : 1u << (c & 0x1f)));
+        assert(d == (c & 0x20 ? 1u << (c & 0x1f) : 0));
+    }
+    return 0;
+}