Re: [PATCH] arm: Fix ICE with CMSE nonsecure call on Armv8.1-M [PR100333]

[Richard Earnshaw via Gcc-patches]

On 19/05/2021 15:44, Alex Coplan via Gcc-patches wrote:

This time with attachment.

On 19/05/2021 15:42, Alex Coplan via Gcc-patches wrote:

Hi Richard,

On 17/05/2021 17:31, Richard Earnshaw wrote:

On 30/04/2021 09:30, Alex Coplan via Gcc-patches wrote:

Hi,

As the PR shows, we ICE shortly after expanding nonsecure calls for
Armv8.1-M.  For Armv8.1-M, we have TARGET_HAVE_FPCXT_CMSE. As it stands,
the expander (arm.md:nonsecure_call_internal) moves the callee's address
to a register (with copy_to_suggested_reg) only if
!TARGET_HAVE_FPCXT_CMSE.

However, looking at the pattern which the insn appears to be intended to
match (thumb2.md:*nonsecure_call_reg_thumb2_fpcxt), it requires the
callee's address to be in a register.

This patch therefore just forces the callee's address into a register in
the expander.

Testing:
   * Regtested an arm-eabi cross configured with
   --with-arch=armv8.1-m.main+mve.fp+fp.dp --with-float=hard. No regressions.
   * Bootstrap and regtest on arm-linux-gnueabihf in progress.

OK for trunk and backports as appropriate if bootstrap looks good?

Thanks,
Alex

gcc/ChangeLog:

        PR target/100333
        * config/arm/arm.md (nonsecure_call_internal): Always ensure
        callee's address is in a register.

gcc/testsuite/ChangeLog:

        PR target/100333
        * gcc.target/arm/cmse/pr100333.c: New test.

-  "
    {
-    if (!TARGET_HAVE_FPCXT_CMSE)
-      {
-       rtx tmp =
-         copy_to_suggested_reg (XEXP (operands[0], 0),
-                                gen_rtx_REG (SImode, R4_REGNUM),
-                                SImode);
+    rtx tmp = NULL_RTX;
+    rtx addr = XEXP (operands[0], 0);

-       operands[0] = replace_equiv_address (operands[0], tmp);
-      }
-  }")
+    if (TARGET_HAVE_FPCXT_CMSE && !REG_P (addr))
+      tmp = force_reg (SImode, addr);
+    else if (!TARGET_HAVE_FPCXT_CMSE)
+      tmp = copy_to_suggested_reg (XEXP (operands[0], 0),
+                                  gen_rtx_REG (SImode, R4_REGNUM),
+                                  SImode);


I think it might be better to handle the !TARGET_HAVE_FPCXT_CMSE case via a
pseudo as well, then we don't end up generating a potentially non-trivial
insn that directly writes a fixed hard reg - it's better to let later passes
clean that up if they can.

Ah, I wasn't aware that was an issue.

Also, you've extracted XEXP (operands[0], 0) into 'addr', but then continue
to use the XEXP form in the existing path.  Please be consistent use XEXP
directly everywhere, or use 'addr' everywhere.

Fixed, thanks.

So you want something like

   addr = XEXP (operands[0], 0);
   if (!REG_P (addr))
     addr = force_reg (SImode, addr);

   if (!T_H_F_C)
     addr = copy...(addr, gen(r4), SImode);

   operands[0] = replace_equiv_addr (operands[0], addr);

R.

How about the attached? Regtested an armv8.1-m.main cross, 
bootstrapped/regtested
on arm-linux-gnueabihf: no issues.

OK for trunk and eventual backports?

Thanks,
Alex

OK.

R.