On 2/11/22 06:26, Richard Biener wrote:
The following attempts to address gimplification of
... = VIEW_CONVERT_EXPR<int[4]>((i & 1) != 0 ? inv : src)[i];
which is problematic since gimplifying the base object
? inv : src produces a register temporary but GIMPLE does not
really support a register as a base for an ARRAY_REF (even
though that's not strictly validated it seems as can be seen
at -O0).
I suppose that isn't easy to fix?
And COMPONENT_REF has the same problem?
Interestingly the C++ frontend avoids this issue
by emitting the following GENERIC instead:
... = (i & 1) != 0 ? VIEW_CONVERT_EXPR<int[4]>(inv)[i] :
VIEW_CONVERT_EXPR<int[4]>(src)[i];
Yes, because in C++ ?: of two lvalues is an lvalue.
The proposed patch below fixes things up when using an rvalue
as the base is OK by emitting a copy from a register base to a
non-register one. The ?: as lvalue extension seems to be gone
for C, C++ again unwraps the COND_EXPR in that case.
Bootstrapped and tested on x86_64-unknown-linux-gnu.
OK?
OK, assuming "yes" answers to my questions above.
Thanks,
Richard.
2022-02-11 Richard Biener <rguent...@suse.de>
PR middle-end/104497
* gimplify.cc (gimplify_compound_lval): Make sure the
base is a non-register if needed and possible.
* c-c++-common/torture/pr104497.c: New testcase.
---
gcc/gimplify.cc | 17 ++++++++++++++---
gcc/testsuite/c-c++-common/torture/pr104497.c | 12 ++++++++++++
2 files changed, 26 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/c-c++-common/torture/pr104497.c
diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
index 8d676fb96c8..cdf1ccbe48b 100644
--- a/gcc/gimplify.cc
+++ b/gcc/gimplify.cc
@@ -250,6 +250,7 @@ static enum gimplify_status gimplify_compound_expr (tree *,
gimple_seq *, bool);
static hash_map<tree, tree> *oacc_declare_returns;
static enum gimplify_status gimplify_expr (tree *, gimple_seq *, gimple_seq *,
bool (*) (tree), fallback_t, bool);
+static void prepare_gimple_addressable (tree *, gimple_seq *);
/* Shorter alias name for the above function for use in gimplify.cc
only. */
@@ -3126,10 +3127,12 @@ gimplify_compound_lval (tree *expr_p, gimple_seq
*pre_p, gimple_seq *post_p,
gimplified before gimplifying the size expressions.
So we do this in three steps. First we deal with variable
- bounds, sizes, and positions, then we gimplify the base,
- then we deal with the annotations for any variables in the
- components and any indices, from left to right. */
+ bounds, sizes, and positions, then we gimplify the base and
+ ensure it is memory if needed, then we deal with the annotations
+ for any variables in the components and any indices, from left
+ to right. */
+ bool need_non_reg = false;
for (i = expr_stack.length () - 1; i >= 0; i--)
{
tree t = expr_stack[i];
@@ -3165,6 +3168,7 @@ gimplify_compound_lval (tree *expr_p, gimple_seq *pre_p,
gimple_seq *post_p,
TREE_OPERAND (t, 3) = elmt_size;
}
}
+ need_non_reg = true;
}
else if (TREE_CODE (t) == COMPONENT_REF)
{
@@ -3186,6 +3190,7 @@ gimplify_compound_lval (tree *expr_p, gimple_seq *pre_p,
gimple_seq *post_p,
TREE_OPERAND (t, 2) = offset;
}
}
+ need_non_reg = true;
}
}
@@ -3196,6 +3201,12 @@ gimplify_compound_lval (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
fallback | fb_lvalue);
ret = MIN (ret, tret);
+ /* Step 2a: if we have component references we do not support on
+ registers then make sure the base isn't a register. Of course
+ we can only do so if an rvalue is OK. */
+ if (need_non_reg && (fallback & fb_rvalue))
+ prepare_gimple_addressable (p, pre_p);
+
/* Step 3: gimplify size expressions and the indices and operands of
ARRAY_REF. During this loop we also remove any useless conversions. */
diff --git a/gcc/testsuite/c-c++-common/torture/pr104497.c b/gcc/testsuite/c-c++-common/torture/pr104497.c
new file mode 100644
index 00000000000..c63fc021e03
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/torture/pr104497.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+
+typedef int __attribute__((vector_size(16))) vec_t;
+
+vec_t src, inv, res;
+
+void test(int i)
+{
+ vec_t y={0};
+ y[i] = (i & 1 ? inv : src)[i];
+ res = y;
+}