[PATCH 2/2] vect: Make partial trapping ops use predication [PR96373]

[Richard Sandiford <richard.sandiford@arm.com>]

PR96373 points out that a predicated SVE loop currently converts
trapping unconditional ops into unpredicated vector ops.  Doing
the operation on inactive lanes can then raise an exception.

As discussed in the PR trail, we aren't 100% consistent about
whether we preserve traps or not.  But the direction of travel
is clearly to improve that rather than live with it.  This patch
tries to do that for the SVE case.

Doing this regresses gcc.target/aarch64/sve/fabd_1.c.  I've added
-fno-trapping-math for now and filed PR108571 to track it.
A similar problem applies to fsubr_1.d.

I think this is likely to regress Power 10, since conditional
operations are only available for masked loops.  I think we'll
need to add -fno-trapping-math to any affected testcases,
but I don't have a Power 10 system to test on.  Kewen, would you
mind giving this a spin and seeing how bad the fallout is?

Tested on aarch64-linux-gnu.  OK to install assuming no blockers
on the Power 10 side?

Richard


gcc/
	PR tree-optimization/96373
	* tree-vect-stmts.cc (vectorizable_operation): Predicate trapping
	operations on the loop mask.  Reject partial vectors if this isn't
	possible.

gcc/testsuite/
	PR tree-optimization/96373
	PR tree-optimization/108571
	* gcc.target/aarch64/sve/fabd_1.c: Add -fno-trapping-math.
	* gcc.target/aarch64/sve/fsubr_1.c: Likewise.
	* gcc.target/aarch64/sve/fmul_1.c: Expect predicate ops.
	* gcc.target/aarch64/sve/fp_arith_1.c: Likewise.
---
 gcc/testsuite/gcc.target/aarch64/sve/fabd_1.c |  2 +-
 gcc/testsuite/gcc.target/aarch64/sve/fmul_1.c | 12 +++----
 .../gcc.target/aarch64/sve/fp_arith_1.c       | 12 +++----
 .../gcc.target/aarch64/sve/fsubr_1.c          |  2 +-
 gcc/tree-vect-stmts.cc                        | 32 ++++++++++++++-----
 5 files changed, 38 insertions(+), 22 deletions(-)

diff --git a/gcc/testsuite/gcc.target/aarch64/sve/fabd_1.c b/gcc/testsuite/gcc.target/aarch64/sve/fabd_1.c
index 13ad83be24c..30bde6f0df7 100644
--- a/gcc/testsuite/gcc.target/aarch64/sve/fabd_1.c
+++ b/gcc/testsuite/gcc.target/aarch64/sve/fabd_1.c
@@ -1,5 +1,5 @@
 /* { dg-do assemble { target aarch64_asm_sve_ok } } */
-/* { dg-options "-O3 --save-temps" } */
+/* { dg-options "-O3 --save-temps -fno-trapping-math" } */
 
 #define N 16
 
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/fmul_1.c b/gcc/testsuite/gcc.target/aarch64/sve/fmul_1.c
index 4a3e7c06745..0245a8c1422 100644
--- a/gcc/testsuite/gcc.target/aarch64/sve/fmul_1.c
+++ b/gcc/testsuite/gcc.target/aarch64/sve/fmul_1.c
@@ -27,20 +27,20 @@ DO_ARITH_OPS (_Float16, *, mul)
 DO_ARITH_OPS (float, *, mul)
 DO_ARITH_OPS (double, *, mul)
 
-/* { dg-final { scan-assembler-times {\tfmul\tz[0-9]+\.h, z[0-9]+\.h, z[0-9]+\.h\n} 4 } } */
+/* { dg-final { scan-assembler-times {\tfmul\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, z[0-9]+\.h\n} 4 } } */
 /* { dg-final { scan-assembler-times {\tfmul\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, #0.5\n} 1 } } */
-/* { dg-final { scan-assembler-not   {\tfmul\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, #2} } } */
+/* { dg-final { scan-assembler-times {\tfmul\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, #2.0\n} 1 } } */
 /* { dg-final { scan-assembler-not   {\tfmul\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, #5} } } */
 /* { dg-final { scan-assembler-not   {\tfmul\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, #-} } } */
 
-/* { dg-final { scan-assembler-times {\tfmul\tz[0-9]+\.s, z[0-9]+\.s, z[0-9]+\.s\n} 4 } } */
+/* { dg-final { scan-assembler-times {\tfmul\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, z[0-9]+\.s\n} 4 } } */
 /* { dg-final { scan-assembler-times {\tfmul\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, #0.5\n} 1 } } */
-/* { dg-final { scan-assembler-not   {\tfmul\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, #2} } } */
+/* { dg-final { scan-assembler-times {\tfmul\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, #2.0\n} 1 } } */
 /* { dg-final { scan-assembler-not   {\tfmul\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, #5} } } */
 /* { dg-final { scan-assembler-not   {\tfmul\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, #-} } } */
 
-/* { dg-final { scan-assembler-times {\tfmul\tz[0-9]+\.d, z[0-9]+\.d, z[0-9]+\.d\n} 4 } } */
+/* { dg-final { scan-assembler-times {\tfmul\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, z[0-9]+\.d\n} 4 } } */
 /* { dg-final { scan-assembler-times {\tfmul\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, #0.5\n} 1 } } */
-/* { dg-final { scan-assembler-not   {\tfmul\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, #2} } } */
+/* { dg-final { scan-assembler-times {\tfmul\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, #2.0\n} 1 } } */
 /* { dg-final { scan-assembler-not   {\tfmul\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, #5} } } */
 /* { dg-final { scan-assembler-not   {\tfmul\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, #-} } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/fp_arith_1.c b/gcc/testsuite/gcc.target/aarch64/sve/fp_arith_1.c
index 5aed0dcb490..419d6e1b5ec 100644
--- a/gcc/testsuite/gcc.target/aarch64/sve/fp_arith_1.c
+++ b/gcc/testsuite/gcc.target/aarch64/sve/fp_arith_1.c
@@ -34,37 +34,37 @@ DO_ARITH_OPS (double, -, minus)
 
 /* No specific count because it's valid to use fadd or fsub for the
    out-of-range constants.  */
-/* { dg-final { scan-assembler {\tfadd\tz[0-9]+\.h, z[0-9]+\.h, z[0-9]+\.h\n} } } */
+/* { dg-final { scan-assembler {\tfadd\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, z[0-9]+\.h\n} } } */
 /* { dg-final { scan-assembler-times {\tfadd\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, #1.0\n} 2 } } */
 /* { dg-final { scan-assembler-times {\tfadd\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, #0.5\n} 2 } } */
 /* { dg-final { scan-assembler-not   {\tfadd\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, #2} } } */
 /* { dg-final { scan-assembler-not   {\tfadd\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, #-} } } */
 
-/* { dg-final { scan-assembler {\tfsub\tz[0-9]+\.h, z[0-9]+\.h, z[0-9]+\.h\n} } } */
+/* { dg-final { scan-assembler {\tfsub\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, z[0-9]+\.h\n} } } */
 /* { dg-final { scan-assembler-times {\tfsub\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, #1.0\n} 2 } } */
 /* { dg-final { scan-assembler-times {\tfsub\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, #0.5\n} 2 } } */
 /* { dg-final { scan-assembler-not   {\tfsub\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, #2} } } */
 /* { dg-final { scan-assembler-not   {\tfsub\tz[0-9]+\.h, p[0-7]/m, z[0-9]+\.h, #-} } } */
 
-/* { dg-final { scan-assembler {\tfadd\tz[0-9]+\.s, z[0-9]+\.s, z[0-9]+\.s\n} } } */
+/* { dg-final { scan-assembler {\tfadd\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, z[0-9]+\.s\n} } } */
 /* { dg-final { scan-assembler-times {\tfadd\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, #1.0\n} 2 } } */
 /* { dg-final { scan-assembler-times {\tfadd\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, #0.5\n} 2 } } */
 /* { dg-final { scan-assembler-not   {\tfadd\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, #2} } } */
 /* { dg-final { scan-assembler-not   {\tfadd\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, #-} } } */
 
-/* { dg-final { scan-assembler {\tfsub\tz[0-9]+\.s, z[0-9]+\.s, z[0-9]+\.s\n} } } */
+/* { dg-final { scan-assembler {\tfsub\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, z[0-9]+\.s\n} } } */
 /* { dg-final { scan-assembler-times {\tfsub\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, #1.0\n} 2 } } */
 /* { dg-final { scan-assembler-times {\tfsub\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, #0.5\n} 2 } } */
 /* { dg-final { scan-assembler-not   {\tfsub\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, #2} } } */
 /* { dg-final { scan-assembler-not   {\tfsub\tz[0-9]+\.s, p[0-7]/m, z[0-9]+\.s, #-} } } */
 
-/* { dg-final { scan-assembler {\tfadd\tz[0-9]+\.d, z[0-9]+\.d, z[0-9]+\.d\n} } } */
+/* { dg-final { scan-assembler {\tfadd\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, z[0-9]+\.d\n} } } */
 /* { dg-final { scan-assembler-times {\tfadd\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, #1.0\n} 2 } } */
 /* { dg-final { scan-assembler-times {\tfadd\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, #0.5\n} 2 } } */
 /* { dg-final { scan-assembler-not   {\tfadd\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, #2} } } */
 /* { dg-final { scan-assembler-not   {\tfadd\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, #-} } } */
 
-/* { dg-final { scan-assembler {\tfsub\tz[0-9]+\.d, z[0-9]+\.d, z[0-9]+\.d\n} } } */
+/* { dg-final { scan-assembler {\tfsub\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, z[0-9]+\.d\n} } } */
 /* { dg-final { scan-assembler-times {\tfsub\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, #1.0\n} 2 } } */
 /* { dg-final { scan-assembler-times {\tfsub\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, #0.5\n} 2 } } */
 /* { dg-final { scan-assembler-not   {\tfsub\tz[0-9]+\.d, p[0-7]/m, z[0-9]+\.d, #2} } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/fsubr_1.c b/gcc/testsuite/gcc.target/aarch64/sve/fsubr_1.c
index f47a360dee9..012cf6e9e5d 100644
--- a/gcc/testsuite/gcc.target/aarch64/sve/fsubr_1.c
+++ b/gcc/testsuite/gcc.target/aarch64/sve/fsubr_1.c
@@ -1,5 +1,5 @@
 /* { dg-do assemble { target aarch64_asm_sve_ok } } */
-/* { dg-options "-O3 --save-temps" } */
+/* { dg-options "-O3 --save-temps -fno-trapping-math" } */
 
 #define DO_IMMEDIATE_OPS(VALUE, TYPE, NAME)			\
 void vsubrarithimm_##NAME##_##TYPE (TYPE *dst, int count)	\
diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index eb4ca1f184e..56e3c30658e 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -6301,6 +6301,7 @@ vectorizable_operation (vec_info *vinfo,
   int reduc_idx = STMT_VINFO_REDUC_IDX (stmt_info);
   vec_loop_masks *masks = (loop_vinfo ? &LOOP_VINFO_MASKS (loop_vinfo) : NULL);
   internal_fn cond_fn = get_conditional_internal_fn (code);
+  bool could_trap = gimple_could_trap_p (stmt);
 
   if (!vec_stmt) /* transformation not required.  */
     {
@@ -6309,7 +6310,7 @@ vectorizable_operation (vec_info *vinfo,
 	 keeping the inactive lanes as-is.  */
       if (loop_vinfo
 	  && LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo)
-	  && reduc_idx >= 0)
+	  && (could_trap || reduc_idx >= 0))
 	{
 	  if (cond_fn == IFN_LAST
 	      || !direct_internal_fn_supported_p (cond_fn, vectype,
@@ -6452,16 +6453,31 @@ vectorizable_operation (vec_info *vinfo,
       vop1 = ((op_type == binary_op || op_type == ternary_op)
 	      ? vec_oprnds1[i] : NULL_TREE);
       vop2 = ((op_type == ternary_op) ? vec_oprnds2[i] : NULL_TREE);
-      if (masked_loop_p && reduc_idx >= 0)
+      if (masked_loop_p && (reduc_idx >= 0 || could_trap))
 	{
-	  /* Perform the operation on active elements only and take
-	     inactive elements from the reduction chain input.  */
-	  gcc_assert (!vop2);
-	  vop2 = reduc_idx == 1 ? vop1 : vop0;
 	  tree mask = vect_get_loop_mask (gsi, masks, vec_num * ncopies,
 					  vectype, i);
-	  gcall *call = gimple_build_call_internal (cond_fn, 4, mask,
-						    vop0, vop1, vop2);
+	  auto_vec<tree> vops (5);
+	  vops.quick_push (mask);
+	  vops.quick_push (vop0);
+	  if (vop1)
+	    vops.quick_push (vop1);
+	  if (vop2)
+	    vops.quick_push (vop2);
+	  if (reduc_idx >= 0)
+	    {
+	      /* Perform the operation on active elements only and take
+		 inactive elements from the reduction chain input.  */
+	      gcc_assert (!vop2);
+	      vops.quick_push (reduc_idx == 1 ? vop1 : vop0);
+	    }
+	  else
+	    {
+	      auto else_value = targetm.preferred_else_value
+		(cond_fn, vectype, vops.length () - 1, &vops[1]);
+	      vops.quick_push (else_value);
+	    }
+	  gcall *call = gimple_build_call_internal_vec (cond_fn, vops);
 	  new_temp = make_ssa_name (vec_dest, call);
 	  gimple_call_set_lhs (call, new_temp);
 	  gimple_call_set_nothrow (call, true);
-- 
2.25.1