mips: Fix overaligned function arguments [PR109435]

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

@@ -6271,6 +6271,23 @@ 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.  */
@@ -6279,8 +6296,8 @@ 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)

gcc/testsuite/gcc.target/mips/align-1-n64.c

@@ -0,0 +1,20 @@
+/* Check that typedef alignment does not affect passing of function
+   parameters for N64/N32 ABIs.  */
+/* { dg-do compile { target { "mips*-*-*" } } } */
+/* { dg-options "-mabi=64"  } */
+/* { dg-skip-if "" { *-*-* } { "-flto" } { "" } } */
+
+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\\(\\\$\[0-9\]\\)" } } */

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 "" { *-*-* } { "-flto" } { "" } } */
+
+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\\\$5,1\\d\\d\\(\\\$(sp|fp)\\)" } } */
+/* { dg-final { scan-assembler "\tsw\t\\\$6,1\\d\\d\\(\\\$(sp|fp)\\)" } } */
+/* { dg-final { scan-assembler "\tsw\t\\\$7,1\\d\\d\\(\\\$(sp|fp)\\)" } } */