[gcc r12-5920] pragma: Update target option node when optimization changes [PR103515]

[Kewen Lin]

https://gcc.gnu.org/g:01ad8c54fdca1db3d71bf6c4b861a9d1db3c2a59

commit r12-5920-g01ad8c54fdca1db3d71bf6c4b861a9d1db3c2a59
Author: Kewen Lin <linkw@linux.ibm.com>
Date:   Sun Dec 12 23:27:51 2021 -0600

    pragma: Update target option node when optimization changes [PR103515]
    
    For a function with optimize pragma, it's possible that the target
    options change as optimization options change.  Now we create one
    optimization option node when optimize pragma parsing, but don't
    create target option node for possible target option changes.  It
    makes later processing not detect the target options can actually
    change and further doesn't update the target options accordingly.
    
    This patch is to check whether target options have changed when
    creating one optimization option node for pragma optimize, and
    make one target option node if needed.  The associated test case
    shows the difference.  Without this patch, the function foo1 will
    perform unrolling which is unexpected.  The reason is that flag
    unroll_only_small_loops isn't correctly set for it.  The value
    is updated after parsing function foo2, but doesn't get restored
    later since both decls don't have DECL_FUNCTION_SPECIFIC_TARGET
    set and the hook thinks we don't need to switch.  With this patch,
    there is no unrolling for foo1, which is also consistent with the
    behavior by replacing pragma by attribute whether w/ and w/o this
    patch.
    
    As Martin noted, this change does the similar thing like what his
    previous commit r12-1039 did.
    
    gcc/ChangeLog:
    
            PR target/103515
            * attribs.c (decl_attributes): Check if target options change and
            create one node if so.
    
    gcc/testsuite/ChangeLog:
    
            PR target/103515
            * gcc.target/powerpc/pr103515.c: New test.

Diff:
---
 gcc/attribs.c                               | 13 ++++++++++++-
 gcc/testsuite/gcc.target/powerpc/pr103515.c | 30 +++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/gcc/attribs.c b/gcc/attribs.c
index 32c941506f4..01a9ed66485 100644
--- a/gcc/attribs.c
+++ b/gcc/attribs.c
@@ -607,7 +607,18 @@ decl_attributes (tree *node, tree attributes, int flags,
   if (TREE_CODE (*node) == FUNCTION_DECL
       && optimization_current_node != optimization_default_node
       && !DECL_FUNCTION_SPECIFIC_OPTIMIZATION (*node))
-    DECL_FUNCTION_SPECIFIC_OPTIMIZATION (*node) = optimization_current_node;
+    {
+      DECL_FUNCTION_SPECIFIC_OPTIMIZATION (*node) = optimization_current_node;
+      tree cur_tree
+	= build_target_option_node (&global_options, &global_options_set);
+      tree old_tree = DECL_FUNCTION_SPECIFIC_TARGET (*node);
+      if (!old_tree)
+	old_tree = target_option_default_node;
+      /* The changes on optimization options can cause the changes in
+	 target options, update it accordingly if it's changed.  */
+      if (old_tree != cur_tree)
+	DECL_FUNCTION_SPECIFIC_TARGET (*node) = cur_tree;
+    }
 
   /* If this is a function and the user used #pragma GCC target, add the
      options to the attribute((target(...))) list.  */
diff --git a/gcc/testsuite/gcc.target/powerpc/pr103515.c b/gcc/testsuite/gcc.target/powerpc/pr103515.c
new file mode 100644
index 00000000000..698b9a93037
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr103515.c
@@ -0,0 +1,30 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-rtl-loop2_unroll-optimized" } */
+
+/* The pragma specified for foo2 should not affect foo1.
+   Verify compiler won't perform unrolling for foo1.  */
+
+#define N 1024
+extern int a1[N], b1[N], c1[N];
+extern int a2[N], b2[N], c2[N];
+extern int n;
+
+void
+foo1 ()
+{
+  int i;
+  for (i = 0; i < n; i++)
+    c1[i] += a1[i] + b1[i];
+}
+
+#pragma GCC optimize("O3,unroll-loops")
+void
+foo2 ()
+{
+  int i;
+  for (i = 0; i < n; i++)
+    c2[i] += a2[i] + b2[i];
+}
+
+/* { dg-final { scan-rtl-dump-times "optimized: loop unrolled" 1 "loop2_unroll" } } */
+