commit c2ed018d10328c5cf93aa56b00ba4caf5dace539
Author: Ramana Radhakrishnan <ramana.gcc@gmail.com>
Date:   Fri Nov 11 21:39:22 2022 +0000

    [Patch Arm] Fix PR92999
    
    PR target/92999 is a case where the VFP PCS implementation is
    incorrectly considering homogenous floating point aggregates with FP16
    and BF16 values.
    
    Can someone help me with a bootstrap and regression test on an armhf
    environment ?
    
    Signed-off-by: Ramana Radhakrishnan <ramana.gcc@gmail.com>
    Tested-by: Alex Coplan  <alex.coplan@arm.com>
    Reviewed-by: Richard Earnshaw  <rearnsha@arm.com>
    
            PR target/92999
    
    gcc/ChangeLog:
    
            * config/arm/arm.cc (aapcs_vfp_is_invalid_scalar_in_ha): New
            (aapcs_vfp_sub_candidate): Adjust.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/arm/pr92999.c: New test.

diff --git a/gcc/config/arm/arm.cc b/gcc/config/arm/arm.cc
index 2eb4d51e4a3..cd3e1ffe777 100644
--- a/gcc/config/arm/arm.cc
+++ b/gcc/config/arm/arm.cc
@@ -6281,6 +6281,31 @@ const unsigned int WARN_PSABI_EMPTY_CXX17_BASE = 1U << 0;
 const unsigned int WARN_PSABI_NO_UNIQUE_ADDRESS = 1U << 1;
 const unsigned int WARN_PSABI_ZERO_WIDTH_BITFIELD = 1U << 2;
 
+
+/* The AAPCS VFP ABI allows homogenous aggregates with scalar
+   FP32 and FP64 members.
+   Return
+     true if this is a scalar that is not a proper candidate
+     false if this is a scalar that is an acceptable scalar data
+     type in a homogenous aggregate or if this is not a scalar allowing
+     the tree walk in aapcs_vfp_sub_candidate to continue.
+ */
+static bool
+aapcs_vfp_is_invalid_scalar_in_ha (const_tree inner_type)
+{
+
+  machine_mode mode = TYPE_MODE (inner_type);
+  if (TREE_CODE (inner_type) == REAL_TYPE)
+    {
+      if (mode == DFmode && mode == SFmode)
+	return false;
+      else
+	return true;
+    }
+  else
+    return false;
+}
+
 /* Walk down the type tree of TYPE counting consecutive base elements.
    If *MODEP is VOIDmode, then set it to the first valid floating point
    type.  If a non-floating point type is found, or if a floating point
@@ -6372,6 +6397,10 @@ aapcs_vfp_sub_candidate (const_tree type, machine_mode *modep,
 	    || TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST)
 	  return -1;
 
+	/* We ignore HFA's of FP16 and BF16.  */
+	if (aapcs_vfp_is_invalid_scalar_in_ha (TREE_TYPE (type)))
+	  return -1;
+
 	count = aapcs_vfp_sub_candidate (TREE_TYPE (type), modep,
 					 warn_psabi_flags);
 	if (count == -1
@@ -6455,6 +6484,10 @@ aapcs_vfp_sub_candidate (const_tree type, machine_mode *modep,
 		  }
 	      }
 
+	    /* We ignore HA's of FP16 and BF16.  */
+	    if (aapcs_vfp_is_invalid_scalar_in_ha (TREE_TYPE (field)))
+	      return -1;
+
 	    sub_count = aapcs_vfp_sub_candidate (TREE_TYPE (field), modep,
 						 warn_psabi_flags);
 	    if (sub_count < 0)
@@ -6489,6 +6522,10 @@ aapcs_vfp_sub_candidate (const_tree type, machine_mode *modep,
 	    if (TREE_CODE (field) != FIELD_DECL)
 	      continue;
 
+	    /* We ignore HA's of FP16 and BF16.  */
+	    if (aapcs_vfp_is_invalid_scalar_in_ha (TREE_TYPE (field)))
+		return -1;
+
 	    sub_count = aapcs_vfp_sub_candidate (TREE_TYPE (field), modep,
 						 warn_psabi_flags);
 	    if (sub_count < 0)
diff --git a/gcc/testsuite/gcc.target/arm/pr92999.c b/gcc/testsuite/gcc.target/arm/pr92999.c
new file mode 100644
index 00000000000..faa21fdb7d2
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/pr92999.c
@@ -0,0 +1,31 @@
+/* { dg-do run } */
+/* { dg-options "-mfp16-format=ieee" } */
+
+//
+// Compile with gcc -mfp16-format=ieee
+// Any optimization level is fine.
+//
+// Correct output should be
+// "y.first = 1, y.second = -99"
+//
+// Buggy output is
+// "y.first = -99, y.second = -99"
+//
+#include <stdlib.h>
+struct phalf {
+    __fp16 first;
+    __fp16 second;
+};
+
+struct phalf phalf_copy(struct phalf* src) __attribute__((noinline));
+struct phalf phalf_copy(struct phalf* src) {
+    return *src;
+}
+
+int main() {
+    struct phalf x = { 1.0, -99.0};
+    struct phalf y = phalf_copy(&x);
+    if (y.first != 1.0 && y.second != -99.0)
+	abort();
+    return 0;
+}