[PATCH] store-merging: Fix up >= 64 bit insertion [PR111015]

[PATCH] store-merging: Fix up >= 64 bit insertion [PR111015]

[Jakub Jelinek]

Hi!

The following testcase shows that we mishandle bit insertion for
info->bitsize >= 64.  The problem is in using unsigned HOST_WIDE_INT
shift + subtraction + build_int_cst to compute mask, the shift invokes
UB at compile time for info->bitsize 64 and larger and e.g. on the testcase
with info->bitsize happens to compute mask of 0x3f rather than
0x3f'ffffffff'ffffffff.

The patch fixes that by using wide_int wi::mask + wide_int_to_tree, so it
handles masks in any precision (up to WIDE_INT_MAX_PRECISION ;) ).

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk and
backports?

2023-08-30  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/111015
	* gimple-ssa-store-merging.cc
	(imm_store_chain_info::output_merged_store): Use wi::mask and
	wide_int_to_tree instead of unsigned HOST_WIDE_INT shift and
	build_int_cst to build BIT_AND_EXPR mask.

	* gcc.dg/pr111015.c: New test.

--- gcc/gimple-ssa-store-merging.cc.jj	2023-07-11 13:40:39.049448058 +0200
+++ gcc/gimple-ssa-store-merging.cc	2023-08-29 16:13:12.808434272 +0200
@@ -4687,12 +4687,13 @@ imm_store_chain_info::output_merged_stor
 		    }
 		  else if ((BYTES_BIG_ENDIAN ? start_gap : end_gap) > 0)
 		    {
-		      const unsigned HOST_WIDE_INT imask
-			= (HOST_WIDE_INT_1U << info->bitsize) - 1;
+		      wide_int imask
+			= wi::mask (info->bitsize, false,
+				    TYPE_PRECISION (TREE_TYPE (tem)));
 		      tem = gimple_build (&seq, loc,
 					  BIT_AND_EXPR, TREE_TYPE (tem), tem,
-					  build_int_cst (TREE_TYPE (tem),
-							 imask));
+					  wide_int_to_tree (TREE_TYPE (tem),
+							    imask));
 		    }
 		  const HOST_WIDE_INT shift
 		    = (BYTES_BIG_ENDIAN ? end_gap : start_gap);
--- gcc/testsuite/gcc.dg/pr111015.c.jj	2023-08-29 16:06:38.526938204 +0200
+++ gcc/testsuite/gcc.dg/pr111015.c	2023-08-29 16:19:03.702536015 +0200
@@ -0,0 +1,28 @@
+/* PR tree-optimization/111015 */
+/* { dg-do run { target int128 } } */
+/* { dg-options "-O2" } */
+
+struct S { unsigned a : 4, b : 4; unsigned __int128 c : 70; } d;
+
+__attribute__((noipa)) void
+foo (unsigned __int128 x, unsigned char y, unsigned char z)
+{
+  d.a = y;
+  d.b = z;
+  d.c = x;
+}
+
+int
+main ()
+{
+  foo (-1, 12, 5);
+  if (d.a != 12
+      || d.b != 5
+      || d.c != (-1ULL | (((unsigned __int128) 0x3f) << 64)))
+    __builtin_abort ();
+  foo (0x123456789abcdef0ULL | (((unsigned __int128) 26) << 64), 7, 11);
+  if (d.a != 7
+      || d.b != 11
+      || d.c != (0x123456789abcdef0ULL | (((unsigned __int128) 26) << 64)))
+    __builtin_abort ();
+}

	Jakub

Re: [PATCH] store-merging: Fix up >= 64 bit insertion [PR111015]

[Richard Biener]

On Wed, 30 Aug 2023, Jakub Jelinek wrote:

> Hi!
> 
> The following testcase shows that we mishandle bit insertion for
> info->bitsize >= 64.  The problem is in using unsigned HOST_WIDE_INT
> shift + subtraction + build_int_cst to compute mask, the shift invokes
> UB at compile time for info->bitsize 64 and larger and e.g. on the testcase
> with info->bitsize happens to compute mask of 0x3f rather than
> 0x3f'ffffffff'ffffffff.
> 
> The patch fixes that by using wide_int wi::mask + wide_int_to_tree, so it
> handles masks in any precision (up to WIDE_INT_MAX_PRECISION ;) ).
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk and
> backports?

OK.

Thanks,
Richard.

> 2023-08-30  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR tree-optimization/111015
> 	* gimple-ssa-store-merging.cc
> 	(imm_store_chain_info::output_merged_store): Use wi::mask and
> 	wide_int_to_tree instead of unsigned HOST_WIDE_INT shift and
> 	build_int_cst to build BIT_AND_EXPR mask.
> 
> 	* gcc.dg/pr111015.c: New test.
> 
> --- gcc/gimple-ssa-store-merging.cc.jj	2023-07-11 13:40:39.049448058 +0200
> +++ gcc/gimple-ssa-store-merging.cc	2023-08-29 16:13:12.808434272 +0200
> @@ -4687,12 +4687,13 @@ imm_store_chain_info::output_merged_stor
>  		    }
>  		  else if ((BYTES_BIG_ENDIAN ? start_gap : end_gap) > 0)
>  		    {
> -		      const unsigned HOST_WIDE_INT imask
> -			= (HOST_WIDE_INT_1U << info->bitsize) - 1;
> +		      wide_int imask
> +			= wi::mask (info->bitsize, false,
> +				    TYPE_PRECISION (TREE_TYPE (tem)));
>  		      tem = gimple_build (&seq, loc,
>  					  BIT_AND_EXPR, TREE_TYPE (tem), tem,
> -					  build_int_cst (TREE_TYPE (tem),
> -							 imask));
> +					  wide_int_to_tree (TREE_TYPE (tem),
> +							    imask));
>  		    }
>  		  const HOST_WIDE_INT shift
>  		    = (BYTES_BIG_ENDIAN ? end_gap : start_gap);
> --- gcc/testsuite/gcc.dg/pr111015.c.jj	2023-08-29 16:06:38.526938204 +0200
> +++ gcc/testsuite/gcc.dg/pr111015.c	2023-08-29 16:19:03.702536015 +0200
> @@ -0,0 +1,28 @@
> +/* PR tree-optimization/111015 */
> +/* { dg-do run { target int128 } } */
> +/* { dg-options "-O2" } */
> +
> +struct S { unsigned a : 4, b : 4; unsigned __int128 c : 70; } d;
> +
> +__attribute__((noipa)) void
> +foo (unsigned __int128 x, unsigned char y, unsigned char z)
> +{
> +  d.a = y;
> +  d.b = z;
> +  d.c = x;
> +}
> +
> +int
> +main ()
> +{
> +  foo (-1, 12, 5);
> +  if (d.a != 12
> +      || d.b != 5
> +      || d.c != (-1ULL | (((unsigned __int128) 0x3f) << 64)))
> +    __builtin_abort ();
> +  foo (0x123456789abcdef0ULL | (((unsigned __int128) 26) << 64), 7, 11);
> +  if (d.a != 7
> +      || d.b != 11
> +      || d.c != (0x123456789abcdef0ULL | (((unsigned __int128) 26) << 64)))
> +    __builtin_abort ();
> +}
> 
> 	Jakub
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)