[gcc r13-5256] aarch64: fix ICE in aarch64_layout_arg [PR108411]

[Christophe Lyon <clyon@gcc.gnu.org>]

https://gcc.gnu.org/g:a38c079248411ea9dc0610873b3366192315bfee

commit r13-5256-ga38c079248411ea9dc0610873b3366192315bfee
Author: Christophe Lyon <christophe.lyon@arm.com>
Date:   Mon Jan 16 17:48:25 2023 +0000

    aarch64: fix ICE in aarch64_layout_arg [PR108411]
    
    The previous patch added an assert which should not be applied to PST
    types (Pure Scalable Types) because alignment does not matter in this
    case.  This patch moves the assert after the PST case is handled to
    avoid the ICE.
    
            PR target/108411
            gcc/
            * config/aarch64/aarch64.cc (aarch64_layout_arg): Improve
            comment. Move assert about alignment a bit later.

Diff:
---
 gcc/config/aarch64/aarch64.cc | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index d36b57341b3..d55c250870a 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -7659,7 +7659,18 @@ aarch64_layout_arg (cumulative_args_t pcum_v, const function_arg_info &arg)
        && (currently_expanding_function_start
 	   || currently_expanding_gimple_stmt));
 
-  /* There are several things to note here:
+  /* HFAs and HVAs can have an alignment greater than 16 bytes.  For example:
+
+       typedef struct foo {
+         __Int8x16_t foo[2] __attribute__((aligned(32)));
+       } foo;
+
+     is still a HVA despite its larger-than-normal alignment.
+     However, such over-aligned HFAs and HVAs are guaranteed to have
+     no padding.
+
+     If we exclude HFAs and HVAs from the discussion below, then there
+     are several things to note:
 
      - Both the C and AAPCS64 interpretations of a type's alignment should
        give a value that is no greater than the type's size.
@@ -7704,12 +7715,6 @@ aarch64_layout_arg (cumulative_args_t pcum_v, const function_arg_info &arg)
        would treat the alignment as though it was *equal to* 16 bytes.
 
      Both behaviors were wrong, but in different cases.  */
-  unsigned int alignment
-    = aarch64_function_arg_alignment (mode, type, &abi_break,
-				      &abi_break_packed);
-  gcc_assert (alignment <= 16 * BITS_PER_UNIT
-	      && (!alignment || abi_break < alignment)
-	      && (!abi_break_packed || alignment < abi_break_packed));
 
   pcum->aapcs_arg_processed = true;
 
@@ -7780,6 +7785,14 @@ aarch64_layout_arg (cumulative_args_t pcum_v, const function_arg_info &arg)
 						 &nregs);
   gcc_assert (!sve_p || !allocate_nvrn);
 
+  unsigned int alignment
+    = aarch64_function_arg_alignment (mode, type, &abi_break,
+				      &abi_break_packed);
+
+  gcc_assert ((allocate_nvrn || alignment <= 16 * BITS_PER_UNIT)
+	      && (!alignment || abi_break < alignment)
+	      && (!abi_break_packed || alignment < abi_break_packed));
+
   /* allocate_ncrn may be false-positive, but allocate_nvrn is quite reliable.
      The following code thus handles passing by SIMD/FP registers first.  */