-----Original Message-----
From: Victor Do Nascimento <victor.donascime...@arm.com>
Sent: Monday, September 30, 2024 2:34 PM
To: gcc-patches@gcc.gnu.org
Cc: Tamar Christina <tamar.christ...@arm.com>; richard.guent...@gmail.com;
Victor Do Nascimento <victor.donascime...@arm.com>
Subject: [PATCH] middle-end: Fix ifcvt predicate generation for masked function
calls
Up until now, due to a latent bug in the code for the ifcvt pass,
irrespective of the branch taken in a conditional statement, the
original condition for the if statement was used in masking the
function call.
Thus, for code such as:
if (a[i] > limit)
b[i] = fixed_const;
else
b[i] = fn (a[i]);
we would generate the following (wrong) if-converted tree code:
_1 = a[i_1];
_2 = _1 > limit;
_3 = .MASK_CALL (fn, _1, _2);
cstore_4 = _2 ? fixed_const : _3;
as opposed to the correct expected sequence:
_1 = a[i_1];
_2 = _1 > limit;
_3 = ~_2;
_4 = .MASK_CALL (fn, _1, _3);
cstore_5 = _2 ? fixed_const : _4;
This patch ensures that the correct predicate mask generation is
carried out such that, upon autovectorization, the correct vector
lanes are selected in the vectorized function call.
gcc/ChangeLog:
* tree-if-conv.cc (predicate_statements): Fix handling of
predicated function calls.
gcc/testsuite/ChangeLog:
* gcc.dg/vect/vect-fncall-mask.c: New.
---
gcc/testsuite/gcc.dg/vect/vect-fncall-mask.c | 31 ++++++++++++++++++++
gcc/tree-if-conv.cc | 14 ++++++++-
2 files changed, 44 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/vect/vect-fncall-mask.c
diff --git a/gcc/testsuite/gcc.dg/vect/vect-fncall-mask.c
b/gcc/testsuite/gcc.dg/vect/vect-fncall-mask.c
new file mode 100644
index 00000000000..554488e0630
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/vect-fncall-mask.c
@@ -0,0 +1,31 @@
+/* { dg-do compile { target { aarch64*-*-* } } } */
+/* { dg-additional-options "-march=armv8.2-a+sve -fdump-tree-ifcvt-raw -Ofast"
{ target { aarch64*-*-* } } } */
+
+extern int __attribute__ ((simd, const)) fn (int);
+
+const int N = 20;
+const float lim = 101.0;
+const float cst = -1.0;
+float tot = 0.0;
+
+float b[20];
+float a[20] = { [0 ... 9] = 1.7014118e39, /* If branch. */
+ [10 ... 19] = 100.0 }; /* Else branch. */
+
+int main (void)
+{
+ #pragma omp simd
+ for (int i = 0; i < N; i += 1)
+ {
+ if (a[i] > lim)
+ b[i] = cst;
+ else
+ b[i] = fn (a[i]);
+ tot += b[i];
+ }
+ return (0);
+}
+
+/* { dg-final { scan-tree-dump {gimple_assign <gt_expr, _12, _1, 1.01e\+2,
NULL>} ifcvt } } */
+/* { dg-final { scan-tree-dump {gimple_assign <bit_not_expr, _34, _12, NULL,
NULL>} ifcvt } } */
+/* { dg-final { scan-tree-dump {gimple_call <.MASK_CALL, _3, fn, _2, _34>}
ifcvt } }
*/
diff --git a/gcc/tree-if-conv.cc b/gcc/tree-if-conv.cc
index 0346a1376c5..246a6bb5bd1 100644
--- a/gcc/tree-if-conv.cc
+++ b/gcc/tree-if-conv.cc
@@ -2907,6 +2907,8 @@ predicate_statements (loop_p loop)
This will cause the vectorizer to match the "in branch"
clone variants, and serves to build the mask vector
in a natural way. */
+ tree mask = cond;
+ gimple_seq stmts = NULL;
gcall *call = dyn_cast <gcall *> (gsi_stmt (gsi));
tree orig_fn = gimple_call_fn (call);
int orig_nargs = gimple_call_num_args (call);
@@ -2914,7 +2916,17 @@ predicate_statements (loop_p loop)
args.safe_push (orig_fn);
for (int i = 0; i < orig_nargs; i++)
args.safe_push (gimple_call_arg (call, i));
- args.safe_push (cond);
+ /* If `swap', we invert the mask used for the if branch for use
+ when masking the function call. */
+ if (swap)
+ {
+ tree true_val
+ = constant_boolean_node (true, TREE_TYPE (mask));
+ mask = gimple_build (&stmts, BIT_XOR_EXPR,
+ TREE_TYPE (mask), mask, true_val);
+ }
+ gsi_insert_seq_before (&gsi, stmts, GSI_SAME_STMT);
