Currently expand_constructor when it comes to BLKmode types, we store out
the constructor to memory. But for the zero case, we could just use `const_int
0`
instead for types who are less than or equal to BITS_PER_WORD.
This is only valid if we expanding without a target.
This fixes the storing zeros of `char[3]` and `char[7]` into registers.
Boostrapped and tested on x86_64-linux-gnu.
Build and tested for aarch64-linux-gnu.
PR middle-end/110459
gcc/ChangeLog:
* expr.cc (expand_constructor): For expansion of `{}` without a target
and the size is less than BITS_PER_WORD, just return the constant 0.
gcc/testsuite/ChangeLog:
* g++.target/aarch64/array-return-1.C: New test.
* g++.target/i386/array-return-1.C: New test.
Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
---
gcc/expr.cc | 13 +++++++++++
.../g++.target/aarch64/array-return-1.C | 22 +++++++++++++++++++
.../g++.target/i386/array-return-1.C | 20 +++++++++++++++++
3 files changed, 55 insertions(+)
create mode 100644 gcc/testsuite/g++.target/aarch64/array-return-1.C
create mode 100644 gcc/testsuite/g++.target/i386/array-return-1.C
diff --git a/gcc/expr.cc b/gcc/expr.cc
index b3b46a26626..a230847e8da 100644
--- a/gcc/expr.cc
+++ b/gcc/expr.cc
@@ -9412,6 +9412,19 @@ expand_constructor (tree exp, rtx target, enum
expand_modifier modifier,
return constructor;
}
+ /* For expanding of `{}` (or all zeros) without a target
+ with a non addressable constant constructor which will
+ fit into an integral mode, just return the constant 0. */
+ if (mode == BLKmode
+ && !TREE_ADDRESSABLE (exp)
+ && TREE_CONSTANT (exp)
+ && target == NULL_RTX
+ && modifier == EXPAND_NORMAL
+ && all_zeros_p (exp)
+ && tree_fits_uhwi_p (TYPE_SIZE (type))
+ && tree_to_uhwi (TYPE_SIZE (type)) <= BITS_PER_WORD)
+ return const0_rtx;
+
/* If the CTOR is available in static storage and not mostly
zeros and we can move it by pieces prefer to do so since
that's usually more efficient than performing a series of
diff --git a/gcc/testsuite/g++.target/aarch64/array-return-1.C
b/gcc/testsuite/g++.target/aarch64/array-return-1.C
new file mode 100644
index 00000000000..7c0aa480775
--- /dev/null
+++ b/gcc/testsuite/g++.target/aarch64/array-return-1.C
@@ -0,0 +1,22 @@
+// { dg-do compile }
+// { dg-options "-O2" }
+// { dg-final { check-function-bodies "**" "" "" { target { le } } } }
+
+// PR middle-end/110459
+
+/*
+**_Z7sample2c:
+** and w0, w0, 255
+** ret
+*/
+
+struct array {
+ char data[4];
+};
+
+// There should be no adjustment to the stack
+// { dg-final { scan-assembler-not "sp, sp," } }
+auto sample2(char c) {
+ array buffer = {c, 0, 0, 0};
+ return buffer;
+}
diff --git a/gcc/testsuite/g++.target/i386/array-return-1.C
b/gcc/testsuite/g++.target/i386/array-return-1.C
new file mode 100644
index 00000000000..f11905d01e5
--- /dev/null
+++ b/gcc/testsuite/g++.target/i386/array-return-1.C
@@ -0,0 +1,20 @@
+// { dg-do compile }
+// { dg-options "-O2" }
+// { dg-final { check-function-bodies "**" "" "" { target { ! ia32 } } } }
+
+// PR middle-end/110459
+
+/*
+**_Z7sample2c:
+** movzbl %dil, %eax
+** ret
+*/
+
+struct array {
+ char data[4];
+};
+
+array sample2(char c) {
+ array buffer = {c, 0, 0, 0};
+ return buffer;
+}
--
2.43.0
