Re: [PATCH v2] mips: Fix overaligned function arguments [PR109435]

[Jovan Dmitrovic <Jovan.Dmitrovic@Syrmia.com>]

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Hi,
I am sending a revised patch, now with different tests for N64/N32 and O32 ABIs.
For the O32 ABI, I've skipped the -O0 and -Os pipelines, considering there is a
difference between exact offsets for store instructions (the registers used remain
the same).

Skipping -flto isn't really necessary, so I've removed that part.

I've fixed the Changelog, hopefully I've corrected the mistakes I made.

Regards,
Jovan

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From 05e4ff4d2fbb91ea8040fb10d8d6a130ad24bba7 Mon Sep 17 00:00:00 2001
From: Jovan Dmitrovic <Jovan.Dmitrovic@Syrmia.com>
Date: Mon, 26 Jun 2023 17:00:20 +0200
Subject: [PATCH] mips: Fix overaligned function arguments [PR109435]
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This patch changes alignment for typedef types when passed as
arguments, making the alignment equal to the alignment of
original (aliased) types.

This change makes it impossible for a typedef type to have
alignment that is less than its size.

2023-06-27  Jovan Dmitrović  <jovan.dmitrovic@syrmia.com>

gcc/ChangeLog:
        PR target/109435
	* config/mips/mips.cc (mips_function_arg_alignment): Returns
    the alignment of function argument. In case of typedef type,
    it returns the aligment of the aliased type.
	(mips_function_arg_boundary): Relocated calculation of the
    aligment of function arguments.

gcc/testsuite/ChangeLog:

	* gcc.target/mips/align-1-n64.c: New test.
	* gcc.target/mips/align-1-o32.c: New test.
---
 gcc/config/mips/mips.cc                     | 19 ++++++++++++++++++-
 gcc/testsuite/gcc.target/mips/align-1-n64.c | 19 +++++++++++++++++++
 gcc/testsuite/gcc.target/mips/align-1-o32.c | 20 ++++++++++++++++++++
 3 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/mips/align-1-n64.c
 create mode 100644 gcc/testsuite/gcc.target/mips/align-1-o32.c

diff --git a/gcc/config/mips/mips.cc b/gcc/config/mips/mips.cc
index c1d1691306e..20ba35f754c 100644
--- a/gcc/config/mips/mips.cc
+++ b/gcc/config/mips/mips.cc
@@ -6190,6 +6190,23 @@ mips_arg_partial_bytes (cumulative_args_t cum, const function_arg_info &arg)
   return info.stack_words > 0 ? info.reg_words * UNITS_PER_WORD : 0;
 }
 
+/* Given MODE and TYPE of a function argument, return the alignment in
+   bits.
+   In case of typedef, alignment of its original type is
+   used.  */
+
+static unsigned int
+mips_function_arg_alignment (machine_mode mode, const_tree type)
+{
+  if (!type)
+    return GET_MODE_ALIGNMENT (mode);
+
+  if (is_typedef_decl (TYPE_NAME (type)))
+    type = DECL_ORIGINAL_TYPE (TYPE_NAME (type));
+
+  return TYPE_ALIGN (type);
+}
+
 /* Implement TARGET_FUNCTION_ARG_BOUNDARY.  Every parameter gets at
    least PARM_BOUNDARY bits of alignment, but will be given anything up
    to STACK_BOUNDARY bits if the type requires it.  */
@@ -6198,8 +6215,8 @@ static unsigned int
 mips_function_arg_boundary (machine_mode mode, const_tree type)
 {
   unsigned int alignment;
+  alignment = mips_function_arg_alignment (mode, type);
 
-  alignment = type ? TYPE_ALIGN (type) : GET_MODE_ALIGNMENT (mode);
   if (alignment < PARM_BOUNDARY)
     alignment = PARM_BOUNDARY;
   if (alignment > STACK_BOUNDARY)
diff --git a/gcc/testsuite/gcc.target/mips/align-1-n64.c b/gcc/testsuite/gcc.target/mips/align-1-n64.c
new file mode 100644
index 00000000000..46e718d548d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/mips/align-1-n64.c
@@ -0,0 +1,19 @@
+/* Check that typedef alignment does not affect passing of function
+   parameters for N64/N32 ABIs.  */
+/* { dg-do compile { target { "mips*-*-*" } } } */
+/* { dg-options "-mabi=64"  } */
+
+typedef struct ui8
+{
+  unsigned v[8];
+} uint8 __attribute__ ((aligned(64)));
+
+unsigned
+callee (int x, uint8 a)
+{
+  return a.v[0];
+}
+
+/* { dg-final { scan-assembler "\tsd\t\\\$5,0\\(\\\$\[0-9\]\\)" } } */
+/* { dg-final { scan-assembler "\tsd\t\\\$6,8\\(\\\$\[0-9\]\\)" } } */
+/* { dg-final { scan-assembler "\tsd\t\\\$7,16\\(\\\$\[0-9\]\\)" } } */
diff --git a/gcc/testsuite/gcc.target/mips/align-1-o32.c b/gcc/testsuite/gcc.target/mips/align-1-o32.c
new file mode 100644
index 00000000000..a548632b7f6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/mips/align-1-o32.c
@@ -0,0 +1,20 @@
+/* Check that typedef alignment does not affect passing of function
+   parameters for O32 ABI.  */
+/* { dg-do compile { target { "mips*-*-*" } } } */
+/* { dg-options "-mabi=32"  } */
+/* { dg-skip-if "" { *-*-* } { "-O0" "-Os" } { "" } } */
+
+typedef struct ui8
+{
+  unsigned v[8];
+} uint8 __attribute__ ((aligned(64)));
+
+unsigned
+callee (int x, uint8 a)
+{
+  return a.v[0];
+}
+
+/* { dg-final { scan-assembler "\tsw\t\\\$5,100\\(\\\$sp\\)" } } */
+/* { dg-final { scan-assembler "\tsw\t\\\$6,104\\(\\\$sp\\)" } } */
+/* { dg-final { scan-assembler "\tsw\t\\\$7,108\\(\\\$sp\\)" } } */
-- 
2.34.1