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 --git a/gcc/sched-deps.cc b/gcc/sched-deps.cc
index 08877b344b6496a0582120be65238a8c9139aeac..f9371b81fb41eddad842f0a63133fddf50c59131 100644 (file)
--- 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 (file)
index 0000000..ae15169
--- /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;
+    }
+}