[aarch64] PR107920 - Fix incorrect handling of virtual operands in svld1rq_impl::fold

[Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org>]

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Hi,
The following test:

#include "arm_sve.h"

svint8_t
test_s8(int8_t *x)
{
  return svld1rq_s8 (svptrue_b8 (), &x[0]);
}

ICE's with -march=armv8.2-a+sve -O1 -fno-tree-ccp -fno-tree-forwprop:
during GIMPLE pass: fre
pr107920.c: In function ‘test_s8’:
pr107920.c:7:1: internal compiler error: in execute_todo, at passes.cc:2140
    7 | }
      | ^
0x7b03d0 execute_todo
        ../../gcc/gcc/passes.cc:2140

because of incorrect handling of virtual operands in svld1rq_impl::fold:
 # VUSE <.MEM>
  _5 = MEM <vector(16) signed char> [(signed char * {ref-all})x_3(D)];
  _4 = VEC_PERM_EXPR <_5, _5, { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
12, 13, 14, 15, ... }>;
  # VUSE <.MEM_2(D)>
  return _4;

The attached patch tries to fix the issue by building the replacement
statements in gimple_seq, and passing it to gsi_replace_with_seq_vops,
which resolves the ICE, and results in:
  <bb 2> :
  # VUSE <.MEM_2(D)>
  _5 = MEM <vector(16) signed char> [(signed char * {ref-all})x_3(D)];
  _4 = VEC_PERM_EXPR <_5, _5, { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
12, 13, 14, 15, ... }>;
  # VUSE <.MEM_2(D)>
  return _4;

Bootstrapped+tested on aarch64-linux-gnu.
OK to commit ?

Thanks,
Prathamesh

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diff --git a/gcc/config/aarch64/aarch64-sve-builtins-base.cc b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
index 6347407555f..f5546a65d22 100644
--- a/gcc/config/aarch64/aarch64-sve-builtins-base.cc
+++ b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
@@ -45,6 +45,7 @@
 #include "aarch64-sve-builtins-base.h"
 #include "aarch64-sve-builtins-functions.h"
 #include "ssa.h"
+#include "gimple-fold.h"
 
 using namespace aarch64_sve;
 
@@ -1232,7 +1233,9 @@ public:
 	tree mem_ref_op = fold_build2 (MEM_REF, access_type, arg1, zero);
 	gimple *mem_ref_stmt
 	  = gimple_build_assign (mem_ref_lhs, mem_ref_op);
-	gsi_insert_before (f.gsi, mem_ref_stmt, GSI_SAME_STMT);
+
+	gimple_seq stmts = NULL;
+	gimple_seq_add_stmt_without_update (&stmts, mem_ref_stmt);
 
 	int source_nelts = TYPE_VECTOR_SUBPARTS (access_type).to_constant ();
 	vec_perm_builder sel (lhs_len, source_nelts, 1);
@@ -1245,8 +1248,11 @@ public:
 						   indices));
 	tree mask_type = build_vector_type (ssizetype, lhs_len);
 	tree mask = vec_perm_indices_to_tree (mask_type, indices);
-	return gimple_build_assign (lhs, VEC_PERM_EXPR,
-				    mem_ref_lhs, mem_ref_lhs, mask);
+	gimple *g2 = gimple_build_assign (lhs, VEC_PERM_EXPR,
+					  mem_ref_lhs, mem_ref_lhs, mask);
+	gimple_seq_add_stmt_without_update (&stmts, g2);
+	gsi_replace_with_seq_vops (f.gsi, stmts);
+	return g2;
       }
 
     return NULL;
diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index c2d9c806aee..03cdb2f9f49 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -591,7 +591,7 @@ fold_gimple_assign (gimple_stmt_iterator *si)
    If the statement has a lhs the last stmt in the sequence is expected
    to assign to that lhs.  */
 
-static void
+void
 gsi_replace_with_seq_vops (gimple_stmt_iterator *si_p, gimple_seq stmts)
 {
   gimple *stmt = gsi_stmt (*si_p);
diff --git a/gcc/gimple-fold.h b/gcc/gimple-fold.h
index 7d29ee9a9a4..87ed4e56d25 100644
--- a/gcc/gimple-fold.h
+++ b/gcc/gimple-fold.h
@@ -63,6 +63,7 @@ extern bool arith_code_with_undefined_signed_overflow (tree_code);
 extern gimple_seq rewrite_to_defined_overflow (gimple *, bool = false);
 extern void replace_call_with_value (gimple_stmt_iterator *, tree);
 extern tree tree_vec_extract (gimple_stmt_iterator *, tree, tree, tree, tree);
+extern void gsi_replace_with_seq_vops (gimple_stmt_iterator *, gimple_seq);
 
 /* gimple_build, functionally matching fold_buildN, outputs stmts
    int the provided sequence, matching and simplifying them on-the-fly.
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr107920.c b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr107920.c
new file mode 100644
index 00000000000..11448ed5e68
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr107920.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fno-tree-ccp -fno-tree-forwprop" } */
+
+#include "arm_sve.h"
+
+svint8_t
+test_s8(int8_t *x)
+{
+  return svld1rq_s8 (svptrue_b8 (), &x[0]);
+}