[gcc r13-5154] sched-deps: do not schedule pseudos across calls [PR108117]

[gcc r13-5154] sched-deps: do not schedule pseudos across calls [PR108117]

[Alexander Monakov]

https://gcc.gnu.org/g:733a1b777f16cd397b43a242d9c31761f66d3da8

commit r13-5154-g733a1b777f16cd397b43a242d9c31761f66d3da8
Author: Alexander Monakov <amonakov@ispras.ru>
Date:   Fri Jan 13 21:04:02 2023 +0300

    sched-deps: do not schedule pseudos across calls [PR108117]
    
    Scheduling across calls in the pre-RA scheduler is problematic: we do
    not take liveness info into account, and are thus prone to extending
    lifetime of a pseudo over the loop, requiring a callee-saved hardreg
    or causing a spill.
    
    If current function called a setjmp, lifting an assignment over a call
    may be incorrect if a longjmp would happen before the assignment.
    
    Thanks to Jose Marchesi for testing on AArch64.
    
    gcc/ChangeLog:
    
            PR rtl-optimization/108117
            PR rtl-optimization/108132
            * sched-deps.cc (deps_analyze_insn): Do not schedule across
            calls before reload.
    
    gcc/testsuite/ChangeLog:
    
            PR rtl-optimization/108117
            PR rtl-optimization/108132
            * gcc.dg/pr108117.c: New test.

Diff:
---
 gcc/sched-deps.cc               |  9 ++++++++-
 gcc/testsuite/gcc.dg/pr108117.c | 30 ++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/gcc/sched-deps.cc b/gcc/sched-deps.cc
index 08877b344b6..f9371b81fb4 100644
--- a/gcc/sched-deps.cc
+++ b/gcc/sched-deps.cc
@@ -3688,7 +3688,14 @@ deps_analyze_insn (class deps_desc *deps, rtx_insn *insn)
 
       CANT_MOVE (insn) = 1;
 
-      if (find_reg_note (insn, REG_SETJMP, NULL))
+      if (!reload_completed)
+	{
+	  /* Scheduling across calls may increase register pressure by extending
+	     live ranges of pseudos over the call.  Worse, in presence of setjmp
+	     it may incorrectly move up an assignment over a longjmp.  */
+	  reg_pending_barrier = MOVE_BARRIER;
+	}
+      else if (find_reg_note (insn, REG_SETJMP, NULL))
         {
           /* This is setjmp.  Assume that all registers, not just
              hard registers, may be clobbered by this call.  */
diff --git a/gcc/testsuite/gcc.dg/pr108117.c b/gcc/testsuite/gcc.dg/pr108117.c
new file mode 100644
index 00000000000..ae151693e2f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr108117.c
@@ -0,0 +1,30 @@
+/* { dg-do run } */
+/* { dg-require-effective-target nonlocal_goto } */
+/* { dg-options "-O2 -fschedule-insns" } */
+
+#include <stdio.h>
+#include <setjmp.h>
+
+jmp_buf ex_buf;
+
+__attribute__((noipa))
+void fn_throw(int x)
+{
+   if (x)
+      longjmp(ex_buf, 1);
+}
+
+int main(void)
+{
+    int vb = 0; // NB: not volatile, not modified after setjmp
+
+    if (!setjmp(ex_buf)) {
+        fn_throw(1);
+        vb = 1; // not reached in the abstract machine
+    }
+
+    if (vb) {
+        printf("Failed, vb = %d!\n", vb);
+        return 1;
+    }
+}