SVE intrinsics: Fold svmul with all-zero operands to zero vector

As recently implemented for svdiv, this patch folds svmul to a zero
vector if one of the operands is a zero vector. This transformation is
applied if at least one of the following conditions is met:
- the first operand is all zeros or
- the second operand is all zeros, and the predicate is ptrue or the
predication is _x or _z.

In contrast to constant folding, which was implemented in a previous
patch, this transformation is applied as soon as one of the operands is
a zero vector, while the other operand can be a variable.

The patch was bootstrapped and regtested on aarch64-linux-gnu, no regression.
OK for mainline?

Signed-off-by: Jennifer Schmitz <jschmitz@nvidia.com>

gcc/
	* config/aarch64/aarch64-sve-builtins-base.cc (svmul_impl::fold):
	Add folding of all-zero operands to zero vector.

gcc/testsuite/
	* gcc.target/aarch64/sve/const_fold_mul_1.c: Adjust expected
	outcome.
	* gcc.target/aarch64/sve/fold_mul_zero.c: New test.

3 files changed, 383 insertions, 3 deletions

diff --git a/gcc/config/aarch64/aarch64-sve-builtins-base.cc b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
index 9f8af9b..afce52a 100644
--- a/gcc/config/aarch64/aarch64-sve-builtins-base.cc
+++ b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
@@ -2020,7 +2020,22 @@ public:
   gimple *
   fold (gimple_folder &f) const override
   {
-    return f.fold_const_binary (MULT_EXPR);
+    if (auto *res = f.fold_const_binary (MULT_EXPR))
+      return res;
+
+    /* If one of the operands is all zeros, fold to zero vector.  */
+    tree op1 = gimple_call_arg (f.call, 1);
+    if (integer_zerop (op1))
+      return gimple_build_assign (f.lhs, op1);
+
+    tree pg = gimple_call_arg (f.call, 0);
+    tree op2 = gimple_call_arg (f.call, 2);
+    if (integer_zerop (op2)
+	&& (f.pred != PRED_m
+	    || is_ptrue (pg, f.type_suffix (0).element_bytes)))
+      return gimple_build_assign (f.lhs, build_zero_cst (TREE_TYPE (f.lhs)));
+
+    return NULL;
   }
 };
 
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/const_fold_mul_1.c b/gcc/testsuite/gcc.target/aarch64/sve/const_fold_mul_1.c
index 6d68607..2a00cab 100644
--- a/gcc/testsuite/gcc.target/aarch64/sve/const_fold_mul_1.c
+++ b/gcc/testsuite/gcc.target/aarch64/sve/const_fold_mul_1.c
@@ -35,7 +35,7 @@ svint64_t s64_z_pg (svbool_t pg)
 
 /*
 ** s64_z_pg_0:
-**	mov	z[0-9]+\.d, p[0-7]/z, #0
+**	mov	z[0-9]+\.b, #0
 **	ret
 */
 svint64_t s64_z_pg_0 (svbool_t pg)
@@ -117,7 +117,7 @@ svint64_t s64_z_pg_n (svbool_t pg)
 
 /*
 ** s64_z_pg_n_s64_0:
-**	mov	z[0-9]+\.d, p[0-7]/z, #0
+**	mov	z[0-9]+\.b, #0
 **	ret
 */
 svint64_t s64_z_pg_n_s64_0 (svbool_t pg)
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/fold_mul_zero.c b/gcc/testsuite/gcc.target/aarch64/sve/fold_mul_zero.c
new file mode 100644
index 0000000..a5674fd
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sve/fold_mul_zero.c
@@ -0,0 +1,365 @@
+/* { dg-final { check-function-bodies "**" "" } } */
+/* { dg-options "-O2" } */
+
+#include "arm_sve.h"
+
+/*
+** s64_x_pg_op1:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_x_pg_op1 (svbool_t pg, svint64_t op2)
+{
+  return svmul_x (pg, svdup_s64 (0), op2);
+}
+
+/*
+** s64_z_pg_op1:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_z_pg_op1 (svbool_t pg, svint64_t op2)
+{
+  return svmul_z (pg, svdup_s64 (0), op2);
+}
+
+/*
+** s64_m_pg_op1:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_m_pg_op1 (svbool_t pg, svint64_t op2)
+{
+  return svmul_m (pg, svdup_s64 (0), op2);
+}
+
+/*
+** s64_x_ptrue_op1:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_x_ptrue_op1 (svint64_t op2)
+{
+  return svmul_x (svptrue_b64 (), svdup_s64 (0), op2);
+}
+
+/*
+** s64_z_ptrue_op1:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_z_ptrue_op1 (svint64_t op2)
+{
+  return svmul_z (svptrue_b64 (), svdup_s64 (0), op2);
+}
+
+/*
+** s64_m_ptrue_op1:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_m_ptrue_op1 (svint64_t op2)
+{
+  return svmul_m (svptrue_b64 (), svdup_s64 (0), op2);
+}
+
+/*
+** s64_x_pg_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_x_pg_op2 (svbool_t pg, svint64_t op1)
+{
+  return svmul_x (pg, op1, svdup_s64 (0));
+}
+
+/*
+** s64_z_pg_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_z_pg_op2 (svbool_t pg, svint64_t op1)
+{
+  return svmul_z (pg, op1, svdup_s64 (0));
+}
+
+/*
+** s64_m_pg_op2:
+**	mov	z[0-9]+\.d, p0/m, #0
+**	ret
+*/
+svint64_t s64_m_pg_op2 (svbool_t pg, svint64_t op1)
+{
+  return svmul_m (pg, op1, svdup_s64 (0));
+}
+
+/*
+** s64_x_ptrue_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_x_ptrue_op2 (svint64_t op1)
+{
+  return svmul_x (svptrue_b64 (), op1, svdup_s64 (0));
+}
+
+/*
+** s64_z_ptrue_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_z_ptrue_op2 (svint64_t op1)
+{
+  return svmul_z (svptrue_b64 (), op1, svdup_s64 (0));
+}
+
+/*
+** s64_m_ptrue_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_m_ptrue_op2 (svint64_t op1)
+{
+  return svmul_m (svptrue_b64 (), op1, svdup_s64 (0));
+}
+
+/*
+** s64_n_x_pg_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_n_x_pg_op2 (svbool_t pg, svint64_t op1)
+{
+  return svmul_n_s64_x (pg, op1, 0);
+}
+
+/*
+** s64_n_z_pg_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_n_z_pg_op2 (svbool_t pg, svint64_t op1)
+{
+  return svmul_n_s64_z (pg, op1, 0);
+}
+
+/*
+** s64_n_m_pg_op2:
+**	mov	z[0-9]+\.d, p0/m, #0
+**	ret
+*/
+svint64_t s64_n_m_pg_op2 (svbool_t pg, svint64_t op1)
+{
+  return svmul_n_s64_m (pg, op1, 0);
+}
+
+/*
+** s64_n_x_ptrue_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_n_x_ptrue_op2 (svint64_t op1)
+{
+  return svmul_n_s64_x (svptrue_b64 (), op1, 0);
+}
+
+/*
+** s64_n_z_ptrue_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_n_z_ptrue_op2 (svint64_t op1)
+{
+  return svmul_n_s64_z (svptrue_b64 (), op1, 0);
+}
+
+/*
+** s64_n_m_ptrue_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svint64_t s64_n_m_ptrue_op2 (svint64_t op1)
+{
+  return svmul_n_s64_m (svptrue_b64 (), op1, 0);
+}
+
+/*
+** u64_x_pg_op1:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_x_pg_op1 (svbool_t pg, svuint64_t op2)
+{
+  return svmul_x (pg, svdup_u64 (0), op2);
+}
+
+/*
+** u64_z_pg_op1:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_z_pg_op1 (svbool_t pg, svuint64_t op2)
+{
+  return svmul_z (pg, svdup_u64 (0), op2);
+}
+
+/*
+** u64_m_pg_op1:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_m_pg_op1 (svbool_t pg, svuint64_t op2)
+{
+  return svmul_m (pg, svdup_u64 (0), op2);
+}
+
+/*
+** u64_x_ptrue_op1:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_x_ptrue_op1 (svuint64_t op2)
+{
+  return svmul_x (svptrue_b64 (), svdup_u64 (0), op2);
+}
+
+/*
+** u64_z_ptrue_op1:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_z_ptrue_op1 (svuint64_t op2)
+{
+  return svmul_z (svptrue_b64 (), svdup_u64 (0), op2);
+}
+
+/*
+** u64_m_ptrue_op1:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_m_ptrue_op1 (svuint64_t op2)
+{
+  return svmul_m (svptrue_b64 (), svdup_u64 (0), op2);
+}
+
+/*
+** u64_x_pg_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_x_pg_op2 (svbool_t pg, svuint64_t op1)
+{
+  return svmul_x (pg, op1, svdup_u64 (0));
+}
+
+/*
+** u64_z_pg_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_z_pg_op2 (svbool_t pg, svuint64_t op1)
+{
+  return svmul_z (pg, op1, svdup_u64 (0));
+}
+
+/*
+** u64_m_pg_op2:
+**	mov	z[0-9]+\.d, p0/m, #0
+**	ret
+*/
+svuint64_t u64_m_pg_op2 (svbool_t pg, svuint64_t op1)
+{
+  return svmul_m (pg, op1, svdup_u64 (0));
+}
+
+/*
+** u64_x_ptrue_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_x_ptrue_op2 (svuint64_t op1)
+{
+  return svmul_x (svptrue_b64 (), op1, svdup_u64 (0));
+}
+
+/*
+** u64_z_ptrue_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_z_ptrue_op2 (svuint64_t op1)
+{
+  return svmul_z (svptrue_b64 (), op1, svdup_u64 (0));
+}
+
+/*
+** u64_m_ptrue_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_m_ptrue_op2 (svuint64_t op1)
+{
+  return svmul_m (svptrue_b64 (), op1, svdup_u64 (0));
+}
+
+/*
+** u64_n_x_pg_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_n_x_pg_op2 (svbool_t pg, svuint64_t op1)
+{
+  return svmul_n_u64_x (pg, op1, 0);
+}
+
+/*
+** u64_n_z_pg_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_n_z_pg_op2 (svbool_t pg, svuint64_t op1)
+{
+  return svmul_n_u64_z (pg, op1, 0);
+}
+
+/*
+** u64_n_m_pg_op2:
+**	mov	z[0-9]+\.d, p0/m, #0
+**	ret
+*/
+svuint64_t u64_n_m_pg_op2 (svbool_t pg, svuint64_t op1)
+{
+  return svmul_n_u64_m (pg, op1, 0);
+}
+
+/*
+** u64_n_x_ptrue_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_n_x_ptrue_op2 (svuint64_t op1)
+{
+  return svmul_n_u64_x (svptrue_b64 (), op1, 0);
+}
+
+/*
+** u64_n_z_ptrue_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_n_z_ptrue_op2 (svuint64_t op1)
+{
+  return svmul_n_u64_z (svptrue_b64 (), op1, 0);
+}
+
+/*
+** u64_n_m_ptrue_op2:
+**	mov	z[0-9]+\.b, #0
+**	ret
+*/
+svuint64_t u64_n_m_ptrue_op2 (svuint64_t op1)
+{
+  return svmul_n_u64_m (svptrue_b64 (), op1, 0);
+}
+