[PATCH] libgccjit: Handle truncation and extension for casts [PR 95498]

Antoni Boucher bouanto@zoho.com
Mon Jul 13 00:30:02 GMT 2020


Hello.

As mentioned in bug 95498, some conversions do not work. After 
investigation, it turns out that it's caused by multiple casts on an 
expression where it should do a truncation/extension.

I added a testcase, but for some reasons, the tests only pass when ran 
via `./testsuite/jit/test-cast.c.exe`, not when ran via `make check-jit 
RUNTESTFLAGS="-v -v -v  jit.exp=test-cast.c"`.
Furthermore, some other tests failed, but they also fail on master.

Also, I was under the impression that adding `STRIP_TYPE_NOPS (t_expr);` 
in `playback::context::build_cast` would be a better fix for this, but 
that doesn't fix the issue.
Am I missing something?

It's my first contribution to gcc, so I'd need help for fixing the tests 
and also a confirmation that this is the best way to fix this issue.

Thanks.
-------------- next part --------------
>From 140333077a4c5f8ce80f7e5716eecc90781594fa Mon Sep 17 00:00:00 2001
From: Antoni Boucher <bouanto@zoho.com>
Date: Sun, 5 Jul 2020 19:07:30 -0400
Subject: [PATCH] This patch handles truncation and extension for casts in jit.

2020-07-12  Antoni Boucher  <bouanto@zoho.com>

gcc/jit/
	PR target/95498
	* jit-playback.c: Add support to handle truncation and extension
	in the convert function.

gcc/testsuite/
	PR target/95498
	* jit.dg/all-non-failing-tests.h: New test.
	* jit.dg/test-cast.c: New test.
---
 gcc/jit/jit-playback.c                       | 39 ++++++++----
 gcc/testsuite/jit.dg/all-non-failing-tests.h | 10 +++
 gcc/testsuite/jit.dg/test-cast.c             | 66 ++++++++++++++++++++
 3 files changed, 104 insertions(+), 11 deletions(-)
 create mode 100644 gcc/testsuite/jit.dg/test-cast.c

diff --git a/gcc/jit/jit-playback.c b/gcc/jit/jit-playback.c
index 0fddf04da87..4f4a1080c36 100644
--- a/gcc/jit/jit-playback.c
+++ b/gcc/jit/jit-playback.c
@@ -61,22 +61,39 @@ along with GCC; see the file COPYING3.  If not see
 
 /* gcc::jit::playback::context::build_cast uses the convert.h API,
    which in turn requires the frontend to provide a "convert"
-   function, apparently as a fallback.
-
-   Hence we provide this dummy one, with the requirement that any casts
-   are handled before reaching this.  */
+   function, apparently as a fallback for casts that can be simplified
+   (truncation, extension). */
 extern tree convert (tree type, tree expr);
 
 tree
 convert (tree dst_type, tree expr)
 {
-  gcc_assert (gcc::jit::active_playback_ctxt);
-  gcc::jit::active_playback_ctxt->add_error (NULL, "unhandled conversion");
-  fprintf (stderr, "input expression:\n");
-  debug_tree (expr);
-  fprintf (stderr, "requested type:\n");
-  debug_tree (dst_type);
-  return error_mark_node;
+  tree t_ret = NULL;
+  t_ret = targetm.convert_to_type (dst_type, expr);
+  if (t_ret)
+      return t_ret;
+  enum tree_code dst_code = TREE_CODE (dst_type);
+  switch (dst_code)
+    {
+    case INTEGER_TYPE:
+    case ENUMERAL_TYPE:
+      t_ret = convert_to_integer (dst_type, expr);
+      goto maybe_fold;
+
+    default:
+      gcc_assert (gcc::jit::active_playback_ctxt);
+      gcc::jit::active_playback_ctxt->add_error (NULL, "unhandled conversion");
+      fprintf (stderr, "input expression:\n");
+      debug_tree (expr);
+      fprintf (stderr, "requested type:\n");
+      debug_tree (dst_type);
+      return error_mark_node;
+
+    maybe_fold:
+      if (TREE_CODE (t_ret) != C_MAYBE_CONST_EXPR)
+	t_ret = fold (t_ret);
+      return t_ret;
+    }
 }
 
 namespace gcc {
diff --git a/gcc/testsuite/jit.dg/all-non-failing-tests.h b/gcc/testsuite/jit.dg/all-non-failing-tests.h
index 632ab8cfb2e..a1481699b16 100644
--- a/gcc/testsuite/jit.dg/all-non-failing-tests.h
+++ b/gcc/testsuite/jit.dg/all-non-failing-tests.h
@@ -98,6 +98,13 @@
 #undef create_code
 #undef verify_code
 
+/* test-cast.c */
+#define create_code create_code_cast
+#define verify_code verify_code_cast
+#include "test-cast.c"
+#undef create_code
+#undef verify_code
+
 /* test-compound-assignment.c */
 #define create_code create_code_compound_assignment
 #define verify_code verify_code_compound_assignment
@@ -354,6 +361,9 @@ const struct testcase testcases[] = {
   {"calling_internal_function",
    create_code_calling_internal_function,
    verify_code_calling_internal_function},
+  {"cast",
+   create_code_cast,
+   verify_code_cast},
   {"compound_assignment",
    create_code_compound_assignment,
    verify_code_compound_assignment},
diff --git a/gcc/testsuite/jit.dg/test-cast.c b/gcc/testsuite/jit.dg/test-cast.c
new file mode 100644
index 00000000000..2b1e385ae40
--- /dev/null
+++ b/gcc/testsuite/jit.dg/test-cast.c
@@ -0,0 +1,66 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "libgccjit.h"
+
+#include "harness.h"
+
+void
+create_code (gcc_jit_context *ctxt, void *user_data)
+{
+  /* Let's try to inject the equivalent of:
+char
+my_casts (int x)
+{
+   return (char)(long) x;
+}
+   */
+  gcc_jit_type *int_type =
+    gcc_jit_context_get_type (ctxt, GCC_JIT_TYPE_INT);
+  gcc_jit_type *long_type =
+    gcc_jit_context_get_type (ctxt, GCC_JIT_TYPE_LONG);
+  gcc_jit_type *return_type =
+    gcc_jit_context_get_type (ctxt, GCC_JIT_TYPE_CHAR);
+
+  gcc_jit_param *x =
+    gcc_jit_context_new_param (
+      ctxt,
+      NULL,
+      int_type, "x");
+  gcc_jit_param *params[1] = {x};
+  gcc_jit_function *func =
+    gcc_jit_context_new_function (ctxt,
+				  NULL,
+				  GCC_JIT_FUNCTION_EXPORTED,
+				  return_type,
+				  "my_casts",
+				  1, params, 0);
+
+  gcc_jit_block *initial =
+    gcc_jit_function_new_block (func, "initial");
+
+  gcc_jit_block_end_with_return(initial, NULL,
+    gcc_jit_context_new_cast(ctxt,
+        NULL,
+        gcc_jit_context_new_cast(ctxt,
+            NULL,
+            gcc_jit_param_as_rvalue(x),
+            long_type
+        ),
+        return_type
+    ));
+}
+
+void
+verify_code (gcc_jit_context *ctxt, gcc_jit_result *result)
+{
+  typedef int (*my_casts_fn_type) (int);
+  CHECK_NON_NULL (result);
+  my_casts_fn_type my_casts =
+    (my_casts_fn_type)gcc_jit_result_get_code (result, "my_casts");
+  CHECK_NON_NULL (my_casts);
+  char val = my_casts (10);
+  note ("my_casts returned: %d", val);
+  CHECK_VALUE (val, 10);
+}
-- 
2.27.0



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