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PR middle-end/83654
* explow.c (anti_adjust_stack_and_probe_stack_clash): Test a
non-constant residual for zero at runtime and avoid probing in
that case. Reorganize code for trailing problem to mirror handling
of the residual.
PR middle-end/83654
* gcc.target/i386/stack-check-18.c: New test.
* gcc.target/i386/stack-check-19.c: New test.
diff --git a/gcc/explow.c b/gcc/explow.c
index b6c56602152..042e71904ec 100644
--- a/gcc/explow.c
+++ b/gcc/explow.c
@@ -1997,11 +1997,27 @@ anti_adjust_stack_and_probe_stack_clash (rtx size)
if (residual != CONST0_RTX (Pmode))
{
+ rtx label = NULL_RTX;
+ /* RESIDUAL could be zero at runtime and in that case *sp could
+ hold live data. Furthermore, we do not want to probe into the
+ red zone.
+
+ Go ahead and just guard the probe at *sp on RESIDUAL != 0 at
+ runtime if RESIDUAL is not a compile time constant. */
+ if (!CONST_INT_P (residual))
+ {
+ label = gen_label_rtx ();
+ emit_cmp_and_jump_insns (residual, CONST0_RTX (GET_MODE (residual)),
+ EQ, NULL_RTX, Pmode, 1, label);
+ }
+
rtx x = force_reg (Pmode, plus_constant (Pmode, residual,
-GET_MODE_SIZE (word_mode)));
anti_adjust_stack (residual);
emit_stack_probe (gen_rtx_PLUS (Pmode, stack_pointer_rtx, x));
emit_insn (gen_blockage ());
+ if (!CONST_INT_P (residual))
+ emit_label (label);
}
/* Some targets make optimistic assumptions in their prologues about
@@ -2014,28 +2030,20 @@ anti_adjust_stack_and_probe_stack_clash (rtx size)
live data. Furthermore, we don't want to probe into the red
zone.
- Go ahead and just guard a probe at *sp on SIZE != 0 at runtime
+ Go ahead and just guard the probe at *sp on SIZE != 0 at runtime
if SIZE is not a compile time constant. */
-
- /* Ideally we would just probe at *sp. However, if SIZE is not
- a compile-time constant, but is zero at runtime, then *sp
- might hold live data. So probe at *sp if we know that
- an allocation was made, otherwise probe into the red zone
- which is obviously undesirable. */
- if (CONST_INT_P (size))
- {
- emit_stack_probe (stack_pointer_rtx);
- emit_insn (gen_blockage ());
- }
- else
+ rtx label = NULL_RTX;
+ if (!CONST_INT_P (size))
{
- rtx label = gen_label_rtx ();
+ label = gen_label_rtx ();
emit_cmp_and_jump_insns (size, CONST0_RTX (GET_MODE (size)),
EQ, NULL_RTX, Pmode, 1, label);
- emit_stack_probe (stack_pointer_rtx);
- emit_insn (gen_blockage ());
- emit_label (label);
}
+
+ emit_stack_probe (stack_pointer_rtx);
+ emit_insn (gen_blockage ());
+ if (!CONST_INT_P (size))
+ emit_label (label);
}
}
diff --git a/gcc/testsuite/gcc.target/i386/stack-check-18.c b/gcc/testsuite/gcc.target/i386/stack-check-18.c
new file mode 100644
index 00000000000..6dbff4402da
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/stack-check-18.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection -mtune=generic -fdump-rtl-expand" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+int f1 (char *);
+
+int
+f2 (void)
+{
+ const int size = 4096;
+ char buffer[size];
+ return f1 (buffer);
+}
+
+/* So we want to verify that at expand time that we probed the main
+ VLA allocation as well as the residuals. Then we want to verify
+ there was only one probe in the final assembly (implying the
+ residual probe was optimized away). */
+/* { dg-final { scan-rtl-dump-times "allocation and probing in loop" 1 "expand" } } */
+/* { dg-final { scan-rtl-dump-times "allocation and probing residuals" 1 "expand" } } */
+
+/* { dg-final { scan-assembler-times "or\[ql\]" 1 } } */
+
diff --git a/gcc/testsuite/gcc.target/i386/stack-check-19.c b/gcc/testsuite/gcc.target/i386/stack-check-19.c
new file mode 100644
index 00000000000..b92c126d57f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/stack-check-19.c
@@ -0,0 +1,29 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection -mtune=generic -fdump-rtl-expand" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+int f1 (char *);
+
+int
+f2 (const int size)
+{
+ char buffer[size];
+ return f1 (buffer);
+}
+
+/* So we want to verify that at expand time that we probed the main
+ VLA allocation as well as the residuals. Then we want to verify
+ there are two probes in the final assembly code. */
+/* { dg-final { scan-rtl-dump-times "allocation and probing in loop" 1 "expand" } } */
+/* { dg-final { scan-rtl-dump-times "allocation and probing residuals" 1 "expand" } } */
+/* { dg-final { scan-assembler-times "or\[ql\]" 2 } } */
+
+/* We also want to verify (indirectly) that the residual probe is
+ guarded. We do that by checking the number of conditional
+ branches. There should be 3. One that bypasses the probe loop, one
+ in the probe loop and one that bypasses the residual probe.
+
+ These will all be equality tests. */
+/* { dg-final { scan-assembler-times "(\?:je|jne)" 3 } } */
+
+