[PATCH] i386: Fix -fcf-protection -Os ICE due to movabsq peephole2 [PR112845]

[PATCH] i386: Fix -fcf-protection -Os ICE due to movabsq peephole2 [PR112845]

[Jakub Jelinek]

Hi!

The following testcase ICEs in the movabsq $(i32 << shift), r64 peephole2
I've added a while back to use smaller code than movabsq if possible.
If i32 is 0xfa1e0ff3 and shift is not divisible by 8, then it creates
an invalid insn (as 0xfa1e0ff3 CONST_INT is not allowed as
x86_64_immediate_operand nor x86_64_zext_immediate_operand), the peephole2
even triggers on it again and again (this time with shift 0) until it gives
up.

The following patch fixes that.  As ix86_endbr_immediate_operand needs a
CONST_INT and it is hopefully rare, I chose to use FAIL rather than handling
it in the condition (where I'd probably need to call ctz_hwi again etc.).

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2023-12-04  Jakub Jelinek  <jakub@redhat.com>

	PR target/112845
	* config/i386/i386.md (movabsq $(i32 << shift), r64 peephole2): FAIL
	if the new immediate is ix86_endbr_immediate_operand.

--- gcc/config/i386/i386.md.jj	2023-12-01 08:10:42.287330513 +0100
+++ gcc/config/i386/i386.md	2023-12-04 16:22:23.497986229 +0100
@@ -2699,7 +2699,10 @@ (define_peephole2
 	      (clobber (reg:CC FLAGS_REG))])]
 {
   int shift = ctz_hwi (UINTVAL (operands[1]));
-  operands[1] = gen_int_mode (UINTVAL (operands[1]) >> shift, DImode);
+  rtx op1 = gen_int_mode (UINTVAL (operands[1]) >> shift, DImode);
+  if (ix86_endbr_immediate_operand (op1, VOIDmode))
+    FAIL;
+  operands[1] = op1;
   operands[2] = gen_int_mode (shift, QImode);
 })
 
--- gcc/testsuite/gcc.dg/pr112845.c.jj	2023-12-04 16:25:31.228350449 +0100
+++ gcc/testsuite/gcc.dg/pr112845.c	2023-12-04 16:25:26.740413464 +0100
@@ -0,0 +1,9 @@
+/* PR target/112845 */
+/* { dg-do compile { target cet } } */
+/* { dg-options "-Os -fcf-protection" } */
+
+unsigned long long
+foo (void)
+{
+  return 0xfa1e0ff3ULL << 3;
+}

	Jakub

Re: [PATCH] i386: Fix -fcf-protection -Os ICE due to movabsq peephole2 [PR112845]

[Uros Bizjak]

On Tue, Dec 5, 2023 at 8:28 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> Hi!
>
> The following testcase ICEs in the movabsq $(i32 << shift), r64 peephole2
> I've added a while back to use smaller code than movabsq if possible.
> If i32 is 0xfa1e0ff3 and shift is not divisible by 8, then it creates
> an invalid insn (as 0xfa1e0ff3 CONST_INT is not allowed as
> x86_64_immediate_operand nor x86_64_zext_immediate_operand), the peephole2
> even triggers on it again and again (this time with shift 0) until it gives
> up.
>
> The following patch fixes that.  As ix86_endbr_immediate_operand needs a
> CONST_INT and it is hopefully rare, I chose to use FAIL rather than handling
> it in the condition (where I'd probably need to call ctz_hwi again etc.).
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2023-12-04  Jakub Jelinek  <jakub@redhat.com>
>
>         PR target/112845
>         * config/i386/i386.md (movabsq $(i32 << shift), r64 peephole2): FAIL
>         if the new immediate is ix86_endbr_immediate_operand.

OK.

Thanks,
Uros.

> --- gcc/config/i386/i386.md.jj  2023-12-01 08:10:42.287330513 +0100
> +++ gcc/config/i386/i386.md     2023-12-04 16:22:23.497986229 +0100
> @@ -2699,7 +2699,10 @@ (define_peephole2
>               (clobber (reg:CC FLAGS_REG))])]
>  {
>    int shift = ctz_hwi (UINTVAL (operands[1]));
> -  operands[1] = gen_int_mode (UINTVAL (operands[1]) >> shift, DImode);
> +  rtx op1 = gen_int_mode (UINTVAL (operands[1]) >> shift, DImode);
> +  if (ix86_endbr_immediate_operand (op1, VOIDmode))
> +    FAIL;
> +  operands[1] = op1;
>    operands[2] = gen_int_mode (shift, QImode);
>  })
>
> --- gcc/testsuite/gcc.dg/pr112845.c.jj  2023-12-04 16:25:31.228350449 +0100
> +++ gcc/testsuite/gcc.dg/pr112845.c     2023-12-04 16:25:26.740413464 +0100
> @@ -0,0 +1,9 @@
> +/* PR target/112845 */
> +/* { dg-do compile { target cet } } */
> +/* { dg-options "-Os -fcf-protection" } */
> +
> +unsigned long long
> +foo (void)
> +{
> +  return 0xfa1e0ff3ULL << 3;
> +}
>
>         Jakub
>