[PATCH] PR target/82166: Update preferred stack boundary for leaf functions
H.J. Lu
hjl.tools@gmail.com
Mon Sep 11 01:57:00 GMT 2017
preferred_stack_boundary may not be the minimum stack alignment. For
leaf functions without TLS access, max_used_stack_slot_alignment may be
smaller. We should update preferred_stack_boundary for leaf functions.
Tested on i686 and x86-64. OK for trunk?
H.J.
---
gcc/
PR target/82166
* config/i386/i386.c (ix86_finalize_stack_frame_flags): Properly
compute the minimum stack alignment. Also update preferred stack
boundary when main () is a leaf function.
gcc/testsuite/
PR target/82166
* gcc.target/i386/pr82166.c: New test.
---
gcc/config/i386/i386.c | 17 ++++++++++++-----
gcc/testsuite/gcc.target/i386/pr82166.c | 14 ++++++++++++++
2 files changed, 26 insertions(+), 5 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/i386/pr82166.c
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 4e93cc1043b..03338e422be 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -14257,11 +14257,12 @@ ix86_finalize_stack_frame_flags (void)
unsigned int incoming_stack_boundary
= (crtl->parm_stack_boundary > ix86_incoming_stack_boundary
? crtl->parm_stack_boundary : ix86_incoming_stack_boundary);
+ unsigned int stack_alignment
+ = (crtl->is_leaf && !ix86_current_function_calls_tls_descriptor
+ ? crtl->max_used_stack_slot_alignment
+ : crtl->stack_alignment_needed);
unsigned int stack_realign
- = (incoming_stack_boundary
- < (crtl->is_leaf && !ix86_current_function_calls_tls_descriptor
- ? crtl->max_used_stack_slot_alignment
- : crtl->stack_alignment_needed));
+ = (incoming_stack_boundary < stack_alignment);
bool recompute_frame_layout_p = false;
if (crtl->stack_realign_finalized)
@@ -14306,7 +14307,9 @@ ix86_finalize_stack_frame_flags (void)
HARD_FRAME_POINTER_REGNUM);
/* The preferred stack alignment is the minimum stack alignment. */
- unsigned int stack_alignment = crtl->preferred_stack_boundary;
+ if (stack_alignment > crtl->preferred_stack_boundary)
+ stack_alignment = crtl->preferred_stack_boundary;
+
bool require_stack_frame = false;
FOR_EACH_BB_FN (bb, cfun)
@@ -14349,6 +14352,10 @@ ix86_finalize_stack_frame_flags (void)
= incoming_stack_boundary;
crtl->stack_alignment_needed
= incoming_stack_boundary;
+ /* Also update preferred_stack_boundary for leaf
+ functions. */
+ crtl->preferred_stack_boundary
+ = incoming_stack_boundary;
}
}
else
diff --git a/gcc/testsuite/gcc.target/i386/pr82166.c b/gcc/testsuite/gcc.target/i386/pr82166.c
new file mode 100644
index 00000000000..8bc63e15231
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr82166.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-Os" } */
+
+void foo (void);
+int a, b, c;
+int
+main (void)
+{
+ int j;
+ for (; c;)
+ a = b;
+ for (; j;)
+ foo ();
+}
--
2.13.5
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