New patch with the requested changes can be found below.
I don't know how much this affects SCEV, but I do believe that we
should incorporate this change somehow. I've seen various cases of
suboptimal address calculation codegen that boil down to this.
gcc/match.pd | 31 +++++++++++++++++++++++++++++++
gcc/testsuite/gcc.dg/pr109393.c | 16 ++++++++++++++++
2 files changed, 47 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/pr109393.c
diff --git a/gcc/match.pd b/gcc/match.pd
index 07e743ae464..1d642c205f0 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3650,6 +3650,37 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(plus (convert @0) (op @2 (convert @1))))))
#endif
+/* ((T)(A + CST1)) * CST2 + CST3
+ -> ((T)(A) * CST2) + ((T)CST1 * CST2 + CST3)
+ Where (A + CST1) doesn't need to have a single use. */
+#if GIMPLE
+ (for op (plus minus)
+ (simplify
+ (plus (mult:s (convert:s (op @0 INTEGER_CST@1)) INTEGER_CST@2)
+ INTEGER_CST@3)
+ (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
+ && INTEGRAL_TYPE_P (type)
+ && TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0))
+ && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))
+ && !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@0))
+ && TYPE_OVERFLOW_WRAPS (type))
+ (op (mult (convert @0) @2) (plus (mult (convert @1) @2) @3)))))
+#endif
+
+/* ((T)(A + CST1)) * CST2 -> ((T)(A) * CST2) + ((T)CST1 * CST2) */
+#if GIMPLE
+ (for op (plus minus)
+ (simplify
+ (mult (convert:s (op:s @0 INTEGER_CST@1)) INTEGER_CST@2)
+ (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
+ && INTEGRAL_TYPE_P (type)
+ && TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0))
+ && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))
+ && !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@0))
+ && TYPE_OVERFLOW_WRAPS (type))
+ (op (mult (convert @0) @2) (mult (convert @1) @2)))))
+#endif
+
/* (T)(A) +- (T)(B) -> (T)(A +- B) only when (A +- B) could be simplified
to a simple value. */
(for op (plus minus)
diff --git a/gcc/testsuite/gcc.dg/pr109393.c b/gcc/testsuite/gcc.dg/pr109393.c
new file mode 100644
index 00000000000..e9051273672
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr109393.c
@@ -0,0 +1,16 @@
+/* PR tree-optimization/109393 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times "return 1;" 2 "optimized" } } */
+
+int foo(int *a, int j)
+{
+ int k = j - 1;
+ return a[j - 1] == a[k];
+}
+
+int bar(int *a, int j)
+{
+ int k = j - 1;
+ return (&a[j + 1] - 2) == &a[k];
+}
--
2.44.0
On Tue, Apr 23, 2024 at 1:33 PM Manolis Tsamis <manolis.tsa...@vrull.eu> wrote:
>
> The original motivation for this pattern was that the following function does
> not fold to 'return 1':
>
> int foo(int *a, int j)
> {
> int k = j - 1;
> return a[j - 1] == a[k];
> }
>
> The expression ((unsigned long) (X +- C1) * C2) appears frequently as part of
> address calculations (e.g. arrays). These patterns help fold and simplify more
> expressions.
>
> PR tree-optimization/109393
>
> gcc/ChangeLog:
>
> * match.pd: Add new patterns for ((T)(A +- CST1)) * CST2 and
> ((T)(A +- CST1)) * CST2 + CST3.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/pr109393.c: New test.
>
> Signed-off-by: Manolis Tsamis <manolis.tsa...@vrull.eu>
> ---
>
> gcc/match.pd | 30 ++++++++++++++++++++++++++++++
> gcc/testsuite/gcc.dg/pr109393.c | 16 ++++++++++++++++
> 2 files changed, 46 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/pr109393.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index d401e7503e6..13c828ba70d 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -3650,6 +3650,36 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (plus (convert @0) (op @2 (convert @1))))))
> #endif
>
> +/* ((T)(A + CST1)) * CST2 + CST3
> + -> ((T)(A) * CST2) + ((T)CST1 * CST2 + CST3)
> + Where (A + CST1) doesn't need to have a single use. */
> +#if GIMPLE
> + (for op (plus minus)
> + (simplify
> + (plus (mult (convert:s (op @0 INTEGER_CST@1)) INTEGER_CST@2)
> INTEGER_CST@3)
> + (if (TREE_CODE (TREE_TYPE (@0)) == INTEGER_TYPE
> + && TREE_CODE (type) == INTEGER_TYPE
> + && TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0))
> + && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))
> + && !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@0))
> + && TYPE_OVERFLOW_WRAPS (type))
> + (op (mult @2 (convert @0)) (plus (mult @2 (convert @1)) @3)))))
> +#endif
> +
> +/* ((T)(A + CST1)) * CST2 -> ((T)(A) * CST2) + ((T)CST1 * CST2) */
> +#if GIMPLE
> + (for op (plus minus)
> + (simplify
> + (mult (convert:s (op:s @0 INTEGER_CST@1)) INTEGER_CST@2)
> + (if (TREE_CODE (TREE_TYPE (@0)) == INTEGER_TYPE
> + && TREE_CODE (type) == INTEGER_TYPE
> + && TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0))
> + && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))
> + && !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@0))
> + && TYPE_OVERFLOW_WRAPS (type))
> + (op (mult @2 (convert @0)) (mult @2 (convert @1))))))
> +#endif
> +
> /* (T)(A) +- (T)(B) -> (T)(A +- B) only when (A +- B) could be simplified
> to a simple value. */
> (for op (plus minus)
> diff --git a/gcc/testsuite/gcc.dg/pr109393.c b/gcc/testsuite/gcc.dg/pr109393.c
> new file mode 100644
> index 00000000000..e9051273672
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr109393.c
> @@ -0,0 +1,16 @@
> +/* PR tree-optimization/109393 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +/* { dg-final { scan-tree-dump-times "return 1;" 2 "optimized" } } */
> +
> +int foo(int *a, int j)
> +{
> + int k = j - 1;
> + return a[j - 1] == a[k];
> +}
> +
> +int bar(int *a, int j)
> +{
> + int k = j - 1;
> + return (&a[j + 1] - 2) == &a[k];
> +}
> --
> 2.34.1
>
