* [PATCH] c++: Fix up ICE on __builtin_shufflevector constexpr evaluation [PR105871]
@ 2022-06-08 6:08 Jakub Jelinek
2022-06-09 12:49 ` Jason Merrill
0 siblings, 1 reply; 2+ messages in thread
From: Jakub Jelinek @ 2022-06-08 6:08 UTC (permalink / raw)
To: Jason Merrill; +Cc: gcc-patches
Hi!
As the following testcase shows, BIT_FIELD_REF result doesn't have to have
just integral type, it can also have vector type. And in that case
cxx_eval_bit_field_ref just ICEs on it because it is unprepared for that
case, creates the initial value with build_int_cst (sure, that one could be
easily replaced with build_zero_cst) and then expects it can through shifts,
ands and ors come up with the final value, but that doesn't work for
vectors.
We already call fold_ternary if whole is a VECTOR_CST, this patch does the
same if the result doesn't have integral type. And, there is no guarantee
fold_ternary will succeed and the callers certainly don't expect NULL
being returned, so it also diagnoses those as non-constant and returns
original t in that case.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2022-06-08 Jakub Jelinek <jakub@redhat.com>
PR c++/105871
* constexpr.cc (cxx_eval_bit_field_ref): For BIT_FIELD_REF with
non-integral result type use fold_ternary too like for BIT_FIELD_REFs
from VECTOR_CST. If fold_ternary returns NULL, diagnose non-constant
expression, set *non_constant_p and return t, instead of returning
NULL.
* g++.dg/pr105871.C: New test.
--- gcc/cp/constexpr.cc.jj 2022-06-03 11:20:13.000000000 +0200
+++ gcc/cp/constexpr.cc 2022-06-07 13:43:13.157127740 +0200
@@ -4198,9 +4198,16 @@ cxx_eval_bit_field_ref (const constexpr_
if (*non_constant_p)
return t;
- if (TREE_CODE (whole) == VECTOR_CST)
- return fold_ternary (BIT_FIELD_REF, TREE_TYPE (t), whole,
- TREE_OPERAND (t, 1), TREE_OPERAND (t, 2));
+ if (TREE_CODE (whole) == VECTOR_CST || !INTEGRAL_TYPE_P (TREE_TYPE (t)))
+ {
+ if (tree r = fold_ternary (BIT_FIELD_REF, TREE_TYPE (t), whole,
+ TREE_OPERAND (t, 1), TREE_OPERAND (t, 2)))
+ return r;
+ if (!ctx->quiet)
+ error ("%qE is not a constant expression", orig_whole);
+ *non_constant_p = true;
+ return t;
+ }
start = TREE_OPERAND (t, 2);
istart = tree_to_shwi (start);
--- gcc/testsuite/g++.dg/pr105871.C.jj 2022-06-07 13:56:02.743241969 +0200
+++ gcc/testsuite/g++.dg/pr105871.C 2022-06-07 13:56:29.042975525 +0200
@@ -0,0 +1,12 @@
+// PR c++/105871
+// { dg-do compile }
+// { dg-options "-Wno-psabi" }
+
+typedef __attribute__((__vector_size__ ( 1))) unsigned char U;
+typedef __attribute__((__vector_size__ (16))) unsigned char V;
+
+U
+foo (void)
+{
+ return __builtin_shufflevector ((U){}, (V){}, 0);
+}
Jakub
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] c++: Fix up ICE on __builtin_shufflevector constexpr evaluation [PR105871]
2022-06-08 6:08 [PATCH] c++: Fix up ICE on __builtin_shufflevector constexpr evaluation [PR105871] Jakub Jelinek
@ 2022-06-09 12:49 ` Jason Merrill
0 siblings, 0 replies; 2+ messages in thread
From: Jason Merrill @ 2022-06-09 12:49 UTC (permalink / raw)
To: Jakub Jelinek; +Cc: gcc-patches
On 6/8/22 02:08, Jakub Jelinek wrote:
> Hi!
>
> As the following testcase shows, BIT_FIELD_REF result doesn't have to have
> just integral type, it can also have vector type. And in that case
> cxx_eval_bit_field_ref just ICEs on it because it is unprepared for that
> case, creates the initial value with build_int_cst (sure, that one could be
> easily replaced with build_zero_cst) and then expects it can through shifts,
> ands and ors come up with the final value, but that doesn't work for
> vectors.
>
> We already call fold_ternary if whole is a VECTOR_CST, this patch does the
> same if the result doesn't have integral type. And, there is no guarantee
> fold_ternary will succeed and the callers certainly don't expect NULL
> being returned, so it also diagnoses those as non-constant and returns
> original t in that case.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
> 2022-06-08 Jakub Jelinek <jakub@redhat.com>
>
> PR c++/105871
> * constexpr.cc (cxx_eval_bit_field_ref): For BIT_FIELD_REF with
> non-integral result type use fold_ternary too like for BIT_FIELD_REFs
> from VECTOR_CST. If fold_ternary returns NULL, diagnose non-constant
> expression, set *non_constant_p and return t, instead of returning
> NULL.
>
> * g++.dg/pr105871.C: New test.
>
> --- gcc/cp/constexpr.cc.jj 2022-06-03 11:20:13.000000000 +0200
> +++ gcc/cp/constexpr.cc 2022-06-07 13:43:13.157127740 +0200
> @@ -4198,9 +4198,16 @@ cxx_eval_bit_field_ref (const constexpr_
> if (*non_constant_p)
> return t;
>
> - if (TREE_CODE (whole) == VECTOR_CST)
> - return fold_ternary (BIT_FIELD_REF, TREE_TYPE (t), whole,
> - TREE_OPERAND (t, 1), TREE_OPERAND (t, 2));
> + if (TREE_CODE (whole) == VECTOR_CST || !INTEGRAL_TYPE_P (TREE_TYPE (t)))
> + {
> + if (tree r = fold_ternary (BIT_FIELD_REF, TREE_TYPE (t), whole,
> + TREE_OPERAND (t, 1), TREE_OPERAND (t, 2)))
> + return r;
> + if (!ctx->quiet)
> + error ("%qE is not a constant expression", orig_whole);
> + *non_constant_p = true;
> + return t;
> + }
>
> start = TREE_OPERAND (t, 2);
> istart = tree_to_shwi (start);
> --- gcc/testsuite/g++.dg/pr105871.C.jj 2022-06-07 13:56:02.743241969 +0200
> +++ gcc/testsuite/g++.dg/pr105871.C 2022-06-07 13:56:29.042975525 +0200
> @@ -0,0 +1,12 @@
> +// PR c++/105871
> +// { dg-do compile }
> +// { dg-options "-Wno-psabi" }
> +
> +typedef __attribute__((__vector_size__ ( 1))) unsigned char U;
> +typedef __attribute__((__vector_size__ (16))) unsigned char V;
> +
> +U
> +foo (void)
> +{
> + return __builtin_shufflevector ((U){}, (V){}, 0);
> +}
>
> Jakub
>
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