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

[Antoni Boucher <bouanto@zoho.com>]

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Here's the patch with the condition removed.
I believe everything is now fixed.
Thanks!

Le jeudi 27 mai 2021 à 18:21 -0400, David Malcolm a écrit :
> On Tue, 2021-05-25 at 20:16 -0400, Antoni Boucher wrote:
> > I updated the patch according to the comments by Tom Tromey.
> > 
> > There's one question left about your question regarding
> > C_MAYBE_CONST_EXPR, David:
> > 
> > I am not sure if we can get a C_MAYBE_CONST_EXPR from libgccjit,
> > and
> > it
> > indeed seems like it's only created in c-family.
> > However, we do use it in libgccjit here:
> > https://github.com/gcc-mirror/gcc/blob/master/gcc/jit/jit-playback.c#L1180
> > 
> > I tried removing the condition `if (TREE_CODE (t_ret) !=
> > C_MAYBE_CONST_EXPR)` and all the tests of libgccjit still pass.
> > 
> > That code was copied from here:
> > https://github.com/gcc-mirror/gcc/blob/master/gcc/c/c-convert.c#L175
> > and might not be needed in libgccjit.
> > 
> > Should I just remove the condition, then?
> 
> I think so.
> 
> Thanks
> Dave
> 
> > 
> > Le jeudi 13 mai 2021 à 19:58 -0400, David Malcolm a écrit :
> > > On Thu, 2021-05-13 at 19:31 -0400, Antoni Boucher wrote:
> > > > Thanks for your answer.
> > > > 
> > > > See my answers below:
> > > > 
> > > > Le jeudi 13 mai 2021 à 18:13 -0400, David Malcolm a écrit :
> > > > > On Sat, 2021-02-20 at 17:17 -0500, Antoni Boucher via Gcc-
> > > > > patches
> > > > > wrote:
> > > > > > Hi.
> > > > > > Thanks for your feedback!
> > > > > > 
> > > > > 
> > > > > Sorry about the delay in responding.
> > > > > 
> > > > > In the past I was hesitant about adding more cast support to
> > > > > libgccjit
> > > > > since I felt that the user could always just create a union
> > > > > to
> > > > > do
> > > > > the
> > > > > cast.  Then I tried actually using the libgccjit API to do
> > > > > this,
> > > > > and
> > > > > realized how much work it adds, so I now think we do want to
> > > > > support
> > > > > casting more types.
> > > > > 
> > > > > 
> > > > > > See answers below:
> > > > > > 
> > > > > > On Sat, Feb 20, 2021 at 11:20:35AM -0700, Tom Tromey wrote:
> > > > > > > > > > > > "Antoni" == Antoni Boucher via Gcc-patches <   
> > > > > > > > > > > > gcc-patches@gcc.gnu.org> writes:
> > > > > > > 
> > > > > > > Antoni> gcc/jit/
> > > > > > > Antoni>         PR target/95498
> > > > > > > Antoni>         * jit-playback.c: Add support to handle
> > > > > > > truncation
> > > > > > > and extension
> > > > > > > Antoni>         in the convert function.
> > > > > > > 
> > > > > > > Antoni> +  switch (dst_code)
> > > > > > > Antoni> +    {
> > > > > > > Antoni> +    case INTEGER_TYPE:
> > > > > > > Antoni> +    case ENUMERAL_TYPE:
> > > > > > > Antoni> +      t_ret = convert_to_integer (dst_type,
> > > > > > > expr);
> > > > > > > Antoni> +      goto maybe_fold;
> > > > > > > Antoni> +
> > > > > > > Antoni> +    default:
> > > > > > > Antoni> +      gcc_assert
> > > > > > > (gcc::jit::active_playback_ctxt);
> > > > > > > Antoni> +      gcc::jit::active_playback_ctxt->add_error
> > > > > > > (NULL,
> > > > > > > "unhandled conversion");
> > > > > > > Antoni> +      fprintf (stderr, "input expression:\n");
> > > > > > > Antoni> +      debug_tree (expr);
> > > > > > > Antoni> +      fprintf (stderr, "requested type:\n");
> > > > > > > Antoni> +      debug_tree (dst_type);
> > > > > > > Antoni> +      return error_mark_node;
> > > > > > > Antoni> +
> > > > > > > Antoni> +    maybe_fold:
> > > > > > > Antoni> +      if (TREE_CODE (t_ret) !=
> > > > > > > C_MAYBE_CONST_EXPR)
> > > > > 
> > > > > Do we even get C_MAYBE_CONST_EXPR in libgccjit?  That tree
> > > > > code
> > > > > is
> > > > > defined in c-family/c-common.def; how can nodes of that kind
> > > > > be
> > > > > created
> > > > > outside of the c-family?
> > > > 
> > > > I am not sure, but that seems like it's only created in c-
> > > > family
> > > > indeed.
> > > > However, we do use it in libgccjit here:
> > > > 
> > > > https://github.com/gcc-mirror/gcc/blob/master/gcc/jit/jit-playback.c#L1180
> > > > 
> > > > > 
> > > > > > > Antoni> +       t_ret = fold (t_ret);
> > > > > > > Antoni> +      return t_ret;
> > > > > > > 
> > > > > > > It seems weird to have a single 'goto' to maybe_fold,
> > > > > > > especially
> > > > > > > inside
> > > > > > > a switch like this.
> > > > > > > 
> > > > > > > If you think the maybe_fold code won't be reused, then it
> > > > > > > should
> > > > > > > just
> > > > > > > be
> > > > > > > hoisted up and the 'goto' removed.
> > > > > > 
> > > > > > This actually depends on how the support for cast between
> > > > > > integers
> > > > > > and 
> > > > > > pointers will be implemented (see below).
> > > > > > If we will support truncating pointers (does that even make
> > > > > > sense?
> > > > > > and
> > > > > > I 
> > > > > > guess we cannot extend a pointer unless we add the support
> > > > > > for 
> > > > > > uint128_t), that label will be reused for that case.
> > > > > > Otherwise, it might not be reused.
> > > > > > 
> > > > > > So, please tell me which option to choose and I'll update
> > > > > > my
> > > > > > patch.
> > > > > 
> > > > > FWIW I don't think we'll want to support truncating or
> > > > > extending
> > > > > pointers.
> > > > 
> > > > Ok, but do you think we'll want to support casts between
> > > > integers
> > > > and
> > > > pointers?
> > > 
> > > Yes, though we probably want to reject truncating a pointer into
> > > a
> > > smaller integer type.
> > > 
> > > > I opened an issue about this
> > > > (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95438) and would
> > > > be
> > > > willing to do a patch for it eventually.
> > > > 
> > > > > > 
> > > > > > > On the other hand, if the maybe_fold code might be reused
> > > > > > > for
> > > > > > > some
> > > > > > > other
> > > > > > > case, then I suppose I would have the case end with
> > > > > > > 'break'
> > > > > > > and
> > > > > > > then
> > > > > > > have this code outside the switch.
> > > > > > > 
> > > > > > > 
> > > > > > > In another message, you wrote:
> > > > > > > 
> > > > > > > Antoni> For your question, the current code already works
> > > > > > > with
> > > > > > > boolean and
> > > > > > > Antoni> reals and casts between integers and pointers is
> > > > > > > currently
> > > > > > > not
> > > > > > > Antoni> supported.
> > > > > > > 
> > > > > > > I am curious why this wasn't supported.  It seems like
> > > > > > > something
> > > > > > > that
> > > > > > > one might want to do.
> > > > > > 
> > > > > > I have no idea as this is my first contribution to gcc.
> > > > > > But this would be indeed very useful and I opened an issue
> > > > > > about
> > > > > > this: 
> > > > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95438
> > > > > > 
> > > > > > > thanks,
> > > > > > > Tom
> > > > > > 
> > > > > > Thanks!
> > > > > > 
> > > > > 
> > > > > 
> > > > 
> > > > 
> > > 
> > > 
> > 
> 
> 


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From 18b9b05268c53368631937e9bdf3086aab8883dd 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 (convert): 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.

Signed-off-by: Antoni Boucher <bouanto@zoho.com>
---
 gcc/jit/jit-playback.c                       | 33 ++++++----
 gcc/testsuite/jit.dg/all-non-failing-tests.h | 10 +++
 gcc/testsuite/jit.dg/test-cast.c             | 66 ++++++++++++++++++++
 3 files changed, 98 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 c6136301243..d26f08bfc1b 100644
--- a/gcc/jit/jit-playback.c
+++ b/gcc/jit/jit-playback.c
@@ -62,22 +62,33 @@ 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:
+      return fold (convert_to_integer (dst_type, expr));
+
+    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;
+    }
 }
 
 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 4202eb7798b..84ef54a0386 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
@@ -361,6 +368,9 @@ 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);
+}
-- 
2.31.1