Hi,
This rejects any loops where any predicated instruction comes before the vctp
that generates the loop predicate. Even though this is not a requirement for
dlstp transformation we have found potential issues where you can end up with a
wrong transformation, so it is safer to reject such loops.
OK for trunk?
gcc/ChangeLog:
* gcc/config/arm/arm.cc (arm_mve_get_loop_vctp): Reject loops with a
predicated instruction before the vctp.
gcc/testsuite/ChangeLog:
* gcc.target/arm/mve/dlstp-invalid-asm.c (test10): Renamed to...
(test10a): ... this.
(test10b): Variation of test10a with a small change to trigger an
issue.
---
gcc/config/arm/arm.cc | 21 ++++++++++++++-----
.../gcc.target/arm/mve/dlstp-invalid-asm.c | 20 +++++++++++++++++-
2 files changed, 35 insertions(+), 6 deletions(-)
diff --git a/gcc/config/arm/arm.cc b/gcc/config/arm/arm.cc
index 7292fddef80..29c0f478f36 100644
--- a/gcc/config/arm/arm.cc
+++ b/gcc/config/arm/arm.cc
@@ -34749,11 +34749,22 @@ arm_mve_get_loop_vctp (basic_block bb)
instruction. We require arm_get_required_vpr_reg_param to be false
to make sure we pick up a VCTP, rather than a VCTP_M. */
FOR_BB_INSNS (bb, insn)
- if (NONDEBUG_INSN_P (insn))
- if (arm_get_required_vpr_reg_ret_val (insn)
- && (arm_mve_get_vctp_lanes (insn) != 0)
- && !arm_get_required_vpr_reg_param (insn))
- return insn;
+ {
+ if (!NONDEBUG_INSN_P (insn))
+ continue;
+ /* If we encounter a predicated instruction before the VCTP then we can
+ not dlstp transform this loop because we would be imposing extra
+ predication on that instruction which was not present in the original
+ code. */
+ if (arm_get_required_vpr_reg_param (insn))
+ return NULL;
+ if (arm_get_required_vpr_reg_ret_val (insn))
+ {
+ if (arm_mve_get_vctp_lanes (insn) != 0)
+ return insn;
+ return NULL;
+ }
+ }
return NULL;
}
diff --git a/gcc/testsuite/gcc.target/arm/mve/dlstp-invalid-asm.c b/gcc/testsuite/gcc.target/arm/mve/dlstp-invalid-asm.c
index 26df2d30523..f26754cc482 100644
--- a/gcc/testsuite/gcc.target/arm/mve/dlstp-invalid-asm.c
+++ b/gcc/testsuite/gcc.target/arm/mve/dlstp-invalid-asm.c
@@ -128,7 +128,7 @@ void test9 (int32_t *a, int32_t *b, int32_t *c, int n)
}
/* Using a VPR that gets re-generated within the loop. */
-void test10 (int32_t *a, int32_t *b, int32_t *c, int n)
+void test10a (int32_t *a, int32_t *b, int32_t *c, int n)
{
mve_pred16_t p = vctp32q (n);
while (n > 0)
@@ -145,6 +145,24 @@ void test10 (int32_t *a, int32_t *b, int32_t *c, int n)
}
}
+/* Using a VPR that gets re-generated within the loop. */
+void test10b (int32_t *a, int32_t *b, int32_t *c, int n)
+{
+ mve_pred16_t p = vctp32q (n-4);
+ while (n > 0)
+ {
+ int32x4_t va = vldrwq_z_s32 (a, p);
+ p = vctp32q (n);
+ int32x4_t vb = vldrwq_z_s32 (b, p);
+ int32x4_t vc = vaddq_x_s32 (va, vb, p);
+ vstrwq_p_s32 (c, vc, p);
+ c += 4;
+ a += 4;
+ b += 4;
+ n -= 4;
+ }
+}
+
/* Using vctp32q_m instead of vctp32q. */
void test11 (int32_t *a, int32_t *b, int32_t *c, int n, mve_pred16_t p0)
{
