@@ -3371,9 +3371,21 @@ ix86_simd_clone_adjust (struct cgraph_node *node)
static void
ix86_set_func_type (tree fndecl)
{
+ /* No need to save and restore callee-saved registers for a noreturn
+ function with nothrow or compiled with -fno-exceptions.
+
+ NB: Don't use TREE_THIS_VOLATILE to check if this is a noreturn
+ function. The local-pure-const pass turns an interrupt function
+ into a noreturn function by setting TREE_THIS_VOLATILE. Normally
+ the local-pure-const pass is run after ix86_set_func_type is called.
+ When the local-pure-const pass is enabled for LTO, the interrupt
+ function is marked as noreturn in the IR output, which leads the
+ incompatible attribute error in LTO1. */
bool has_no_callee_saved_registers
- = lookup_attribute ("no_callee_saved_registers",
- TYPE_ATTRIBUTES (TREE_TYPE (fndecl)));
+ = (((TREE_NOTHROW (fndecl) || !flag_exceptions)
+ && lookup_attribute ("noreturn", DECL_ATTRIBUTES (fndecl)))
+ || lookup_attribute ("no_callee_saved_registers",
+ TYPE_ATTRIBUTES (TREE_TYPE (fndecl))));
if (cfun->machine->func_type == TYPE_UNKNOWN)
{
new file mode 100644
@@ -0,0 +1,26 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mtune-ctrl=^prologue_using_move,^epilogue_using_move" } */
+
+#define ARRAY_SIZE 256
+
+extern int array[ARRAY_SIZE][ARRAY_SIZE][ARRAY_SIZE];
+extern int value (int, int, int)
+#ifndef __x86_64__
+__attribute__ ((regparm(3)))
+#endif
+;
+
+void
+__attribute__((noreturn))
+no_return_to_caller (void)
+{
+ unsigned i, j, k;
+ for (i = ARRAY_SIZE; i > 0; --i)
+ for (j = ARRAY_SIZE; j > 0; --j)
+ for (k = ARRAY_SIZE; k > 0; --k)
+ array[i - 1][j - 1][k - 1] = value (i, j, k);
+ while (1);
+}
+
+/* { dg-final { scan-assembler-not "push" } } */
+/* { dg-final { scan-assembler-not "pop" } } */
new file mode 100644
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mtune-ctrl=^prologue_using_move,^epilogue_using_move" } */
+
+extern void bar (void) __attribute__ ((no_callee_saved_registers));
+extern void fn (void) __attribute__ ((noreturn));
+
+__attribute__ ((noreturn))
+void
+foo (void)
+{
+ bar ();
+ fn ();
+}
+
+/* { dg-final { scan-assembler-not "push" } } */
+/* { dg-final { scan-assembler-not "pop" } } */
+/* { dg-final { scan-assembler-not "jmp\[\\t \]+_?bar" } } */
+/* { dg-final { scan-assembler "call\[\\t \]+_?bar" } } */
new file mode 100644
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mtune-ctrl=^prologue_using_move,^epilogue_using_move" } */
+
+typedef void (*fn_t) (void) __attribute__ ((no_callee_saved_registers));
+extern fn_t bar;
+extern void fn (void) __attribute__ ((noreturn));
+
+__attribute__ ((noreturn))
+void
+foo (void)
+{
+ bar ();
+ fn ();
+}
+
+/* { dg-final { scan-assembler-not "push" } } */
+/* { dg-final { scan-assembler-not "pop" } } */
+/* { dg-final { scan-assembler-not "jmp" } } */
+/* { dg-final { scan-assembler "call\[\\t \]+" } } */
new file mode 100644
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mtune-ctrl=^prologue_using_move,^epilogue_using_move" } */
+
+typedef void (*fn_t) (void) __attribute__ ((no_callee_saved_registers));
+extern void fn (void) __attribute__ ((noreturn));
+
+__attribute__ ((noreturn))
+void
+foo (fn_t bar)
+{
+ bar ();
+ fn ();
+}
+
+/* { dg-final { scan-assembler-not "push" } } */
+/* { dg-final { scan-assembler-not "pop" } } */
+/* { dg-final { scan-assembler-not "jmp" } } */
+/* { dg-final { scan-assembler "call\[\\t \]+" } } */
@@ -23,19 +23,14 @@ f3 (void)
/* Verify no explicit probes. */
/* { dg-final { scan-assembler-not "or\[ql\]" } } */
-/* We also want to verify we did not use a push/pop sequence
- to probe *sp as the callee register saves are sufficient
- to probe *sp.
-
- y0/y1 are live across the call and thus must be allocated
+/* y0/y1 are live across the call and thus must be allocated
into either a stack slot or callee saved register. The former
would be rather dumb. So assume it does not happen.
- So search for two/four pushes for the callee register saves/argument pushes
- (plus one for the PIC register if needed on ia32) and no pops (since the
- function has no reachable epilogue). */
-/* { dg-final { scan-assembler-times "push\[ql\]" 2 { target { ! ia32 } } } } */
-/* { dg-final { scan-assembler-times "push\[ql\]" 4 { target { ia32 && nonpic } } } } */
-/* { dg-final { scan-assembler-times "push\[ql\]" 5 { target { ia32 && { ! nonpic } } } } } */
-/* { dg-final { scan-assembler-not "pop" } } */
+ So search for a push/pop sequence for stack probe and 2 argument
+ pushes on ia32. There is no need to save and restore the PIC
+ register on ia32 for a noreturn function. */
+/* { dg-final { scan-assembler-times "push\[ql\]" 1 { target { ! ia32 } } } } */
+/* { dg-final { scan-assembler-times "push\[ql\]" 3 { target ia32 } } } */
+/* { dg-final { scan-assembler-times "pop" 1 } } */
There is no need to save callee-saved registers in noreturn functions if they don't throw nor support exceptions. We can treat them the same as functions with no_callee_saved_registers attribute. Adjust stack-check-17.c for noreturn function which no longer saves any registers. With this change, __libc_start_main in glibc 2.39, which is a noreturn function, is changed from __libc_start_main: endbr64 push %r15 push %r14 mov %rcx,%r14 push %r13 push %r12 push %rbp mov %esi,%ebp push %rbx mov %rdx,%rbx sub $0x28,%rsp mov %rdi,(%rsp) mov %fs:0x28,%rax mov %rax,0x18(%rsp) xor %eax,%eax test %r9,%r9 to __libc_start_main: endbr64 sub $0x28,%rsp mov %esi,%ebp mov %rdx,%rbx mov %rcx,%r14 mov %rdi,(%rsp) mov %fs:0x28,%rax mov %rax,0x18(%rsp) xor %eax,%eax test %r9,%r9 In Linux kernel 6.7.0 on x86-64, do_exit is changed from do_exit: endbr64 call <do_exit+0x9> push %r15 push %r14 push %r13 push %r12 mov %rdi,%r12 push %rbp push %rbx mov %gs:0x0,%rbx sub $0x28,%rsp mov %gs:0x28,%rax mov %rax,0x20(%rsp) xor %eax,%eax call *0x0(%rip) # <do_exit+0x39> test $0x2,%ah je <do_exit+0x8d3> to do_exit: endbr64 call <do_exit+0x9> sub $0x28,%rsp mov %rdi,%r12 mov %gs:0x28,%rax mov %rax,0x20(%rsp) xor %eax,%eax mov %gs:0x0,%rbx call *0x0(%rip) # <do_exit+0x2f> test $0x2,%ah je <do_exit+0x8c9> I compared GCC master branch bootstrap and test times on a slow machine with 6.6 Linux kernels compiled with the original GCC 13 and the GCC 13 with the backported patch. The performance data isn't precise since the measurements were done on different days with different GCC sources under different 6.6 kernel versions. GCC master branch build time in seconds: before after improvement 30043.75user 30013.16user 0% 1274.85system 1243.72system 2.4% GCC master branch test time in seconds (new tests added): before after improvement 216035.90user 216547.51user 0 27365.51system 26658.54system 2.6% gcc/ PR target/38534 * config/i386/i386-options.cc (ix86_set_func_type): Don't save and restore callee saved registers for a noreturn function with nothrow or compiled with -fno-exceptions. gcc/testsuite/ PR target/38534 * gcc.target/i386/pr38534-1.c: New file. * gcc.target/i386/pr38534-2.c: Likewise. * gcc.target/i386/pr38534-3.c: Likewise. * gcc.target/i386/pr38534-4.c: Likewise. * gcc.target/i386/stack-check-17.c: Updated. --- gcc/config/i386/i386-options.cc | 16 ++++++++++-- gcc/testsuite/gcc.target/i386/pr38534-1.c | 26 +++++++++++++++++++ gcc/testsuite/gcc.target/i386/pr38534-2.c | 18 +++++++++++++ gcc/testsuite/gcc.target/i386/pr38534-3.c | 19 ++++++++++++++ gcc/testsuite/gcc.target/i386/pr38534-4.c | 18 +++++++++++++ .../gcc.target/i386/stack-check-17.c | 19 +++++--------- 6 files changed, 102 insertions(+), 14 deletions(-) create mode 100644 gcc/testsuite/gcc.target/i386/pr38534-1.c create mode 100644 gcc/testsuite/gcc.target/i386/pr38534-2.c create mode 100644 gcc/testsuite/gcc.target/i386/pr38534-3.c create mode 100644 gcc/testsuite/gcc.target/i386/pr38534-4.c