[PATCH v2] gdb/testsuite: fix gdb.reverse/i386-avx-reverse.exp with clang

[Guinevere Larsen]

The test gdb.reverse/i386-avx-reverse.exp was changed by the recent
commit:

    commit 5bf288d5a88ab6d3fa9bd7bd070e624afd264dc6
    Author: Guinevere Larsen <guinevere@redhat.com>
    Date:   Fri Jul 26 17:31:14 2024 -0300

    gdb/record: support AVX instructions VMOVDQ(U|A) when recording

In that commit I added a few calls to the instruction vmovdqa to and
from memory addresses. Because my local gcc testing always had aligned
pointers, I thought this would always work, but clang (and maybe other
compilers) might not do the same, which will cause vmovdqa to segfault,
and the test to fail spectacularly.

This commit fixes that by using the pre-existing precise-aligned-alloc
to allocate the dynamic buffers, forcing them to be aligned to the
required boundary for vmovdqa instruction to work. The code was then
re-shuffled to keep the current clustering of instructions.
---

Changelog for v2:
* Used the pre-existing precise-aligned-alloc file to allocate dynamic
  buffers, which guarantees we can use vmovdqa with them.

---
 gdb/testsuite/gdb.reverse/i386-avx-reverse.c  | 21 ++++++++++++-------
 .../gdb.reverse/i386-avx-reverse.exp          | 18 +++++++++-------
 2 files changed, 23 insertions(+), 16 deletions(-)

diff --git a/gdb/testsuite/gdb.reverse/i386-avx-reverse.c b/gdb/testsuite/gdb.reverse/i386-avx-reverse.c
index b36de10ec6f..edd931b9f8c 100644
--- a/gdb/testsuite/gdb.reverse/i386-avx-reverse.c
+++ b/gdb/testsuite/gdb.reverse/i386-avx-reverse.c
@@ -82,23 +82,23 @@ vmov_test ()
   asm volatile ("vmovq %0, %%xmm15": "=m" (buf1));
 
   /* Test vmovdq style instructions.  */
-  /* For local and dynamic buffers, we can't guarantee they will be aligned.
+  /* For local and global buffers, we can't guarantee they will be aligned.
      However, the aligned and unaligned versions seem to be encoded the same,
-     so testing one is enough to validate both.  */
+     so testing one is enough to validate both.  For safety, though, the
+     dynamic buffers are forced to be 32-bit aligned so vmovdqa can be
+     explicitly tested at least once.  */
 
   /* Operations based on local buffers.  */
   asm volatile ("vmovdqu %0, %%ymm0": : "m"(buf0));
   asm volatile ("vmovdqu %%ymm0, %0": "=m"(buf1));
 
   /* Operations based on global buffers.  */
-  /* Global buffers seem to always be aligned, lets sanity check vmovdqa.  */
-  asm volatile ("vmovdqa %0, %%ymm15": : "m"(global_buf0));
-  asm volatile ("vmovdqa %%ymm15, %0": "=m"(global_buf1));
   asm volatile ("vmovdqu %0, %%ymm0": : "m"(global_buf0));
   asm volatile ("vmovdqu %%ymm0, %0": "=m"(global_buf1));
 
   /* Operations based on dynamic buffers.  */
-  /* The dynamic buffers are not aligned, so we skip vmovdqa.  */
+  asm volatile ("vmovdqa %0, %%ymm15": : "m"(*dyn_buf0));
+  asm volatile ("vmovdqa %%ymm15, %0": "=m"(*dyn_buf1));
   asm volatile ("vmovdqu %0, %%ymm0": : "m"(*dyn_buf0));
   asm volatile ("vmovdqu %%ymm0, %0": "=m"(*dyn_buf1));
 
@@ -210,11 +210,16 @@ vzeroupper_test ()
   return 0; /* end vzeroupper_test  */
 }
 
+/* This include is used to allocate the dynamic buffer and have
+   the pointers aligned to a 32-bit boundary, so we can test instructions
+   that require aligned memory.  */
+#include "precise-aligned-alloc.c"
+
 int
 main ()
 {
-  dyn_buf0 = (char *) malloc(sizeof(char) * 32);
-  dyn_buf1 = (char *) malloc(sizeof(char) * 32);
+  dyn_buf0 = (char *) precise_aligned_alloc(32, sizeof(char) * 32, NULL);
+  dyn_buf1 = (char *) precise_aligned_alloc(32, sizeof(char) * 32, NULL);
   for (int i =0; i < 32; i++)
     {
       dyn_buf0[i] = 0x20 + (i % 16);
diff --git a/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp b/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp
index 4aefbcdbab3..7ed12937391 100644
--- a/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp
+++ b/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp
@@ -39,9 +39,10 @@ standard_testfile
 
 # some targets have leading underscores on assembly symbols.
 set additional_flags [gdb_target_symbol_prefix_flags]
+lappend_include_file alloc_lib $srcdir/lib/precise-aligned-alloc.c
 
 if {[prepare_for_testing "failed to prepare" $testfile $srcfile \
-	 [list debug $additional_flags]]} {
+	 [list debug $additional_flags $alloc_lib]]} {
     return -1
 }
 
@@ -135,30 +136,31 @@ global decimal
 if {[record_full_function "vmov"] == true} {
     # Now execute backwards, checking all instructions.
     test_one_register "vmovdqa" "ymm0" \
-	"0x1f1e1d1c1b1a19181716151413121110, 0x1f1e1d1c1b1a19181716151413121110" \
+	"0x2f2e2d2c2b2a29282726252423222120, 0x2f2e2d2c2b2a29282726252423222120" \
 	"from register: "
     test_one_register "vmovdqu" "ymm15" \
-	"0x1f1e1d1c1b1a19181716151413121110, 0x1f1e1d1c1b1a19181716151413121110" \
+	"0x2f2e2d2c2b2a29282726252423222120, 0x2f2e2d2c2b2a29282726252423222120" \
 	"from register: "
     test_one_register "vmovdqu" "ymm0" \
 	"0x2f2e2d2c2b2a29282726252423222120, 0x2f2e2d2c2b2a29282726252423222120" \
 	"from register: "
 
-    test_one_memory "vmovdqu" "dyn_buf1" "0x0 .repeats 32 times" \
+    test_one_memory "vmovdqu" "dyn_buf1" \
+	    "0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29" \
 	true "dynamic buffer: "
     test_one_register "vmovdqu" "ymm0" \
 	"0x1f1e1d1c1b1a19181716151413121110, 0x1f1e1d1c1b1a19181716151413121110" \
 	"dynamic buffer: "
+    test_one_memory "vmovdqa" "dyn_buf1" "0x0 .repeats 32 times" true
+    test_one_register "vmovdqa" "ymm15" "0x0, 0x0"
 
     # Don't check the full buffer because that'd be too long
     test_one_memory "vmovdqu" "global_buf1" \
-	"0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19" \
-	"global buffer: "
+	"0x0 .repeats 32 times" \
+	false "global buffer: "
     test_one_register "vmovdqu" "ymm0" \
 	"0x3f3e3d3c3b3a39383736353433323130, 0x3f3e3d3c3b3a39383736353433323130" \
 	"global buffer: "
-    test_one_memory "vmovdqa" "global_buf1" "0x0 .repeats 32 times"
-    test_one_register "vmovdqa" "ymm15" "0x0, 0x0"
 
     test_one_memory "vmovdqu" "buf1" "0x0 .repeats 32 times"
     test_one_register "vmovdqu" "ymm0" "0x2726252423222120, 0x0" "local buffer: "
-- 
2.47.0