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Re: [PATCH][ARM][gas] Warn on deprecated ldm r<n>, {..., sp,...} and ldm r<n>, {...,lr,pc,...} forms

On 20/01/15 10:10, Kyrill Tkachov wrote:
On 14/01/15 11:32, Ramana Radhakrishnan wrote:
On Wed, Jan 14, 2015 at 11:12 AM, Richard Earnshaw <> wrote:
On 14/01/15 10:24, Kyrill Tkachov wrote:
Hi all,

ARMv7-A deprecates ldm instructions that use the SP register in their list
as well as ldm instructions that use both LR and PC. GAS should warn
about them.

This patch adds a warning for these forms.
Tests are added/updated.

Tested check-gas in arm-none-eabi and I've had it sitting in my tree
being tested
with gcc for a few months now.

What do people think?

I think firstly, that we should use as_tsktsk for deprecations, rather
than warnings.
as_tsktsk would be better but we need to change a whole load of
deprecations to this form rather than warnings in the ARM port. I
don't think all our other deprecations use tsktsk. I think we need to
move people on when they use this on v7-a and newer revisions of the
Shall we go the way of as_tsktsk then and convert the other deprecation
warnings to as_tsktsk.

That should have been a question :)


I do see some deprecations using as_tsktsk and some using


   I don't like hiding these behind flags or folks will not fix their
issues without the compiler or assembler warning / shouting at them.

I'm still somewhat concerned about the use of SP in LDM lists.  This is
going to make any legacy ABI code generated by GCC (-mapcs-frame) very
verbose.  I don't expect we will want to fix GCC to avoid this sequence.
Personally I think (not very strongly) we should fix GCC to avoid this
sequence if we can and then deprecate all uses of mapcs-frame.
Unfortunately it's one of these options that appears to linger on in
build systems for no apparently good reason.


I'd like opinions from others on this one...



2015-01-14  Kyrylo Tkachov  <>

       * config/tc-arm.c (encode_ldmstm): Add deprecation warning when
       SP or both LR and PC are used in ldm register list.

2015-01-14  Kyrylo Tkachov  <>

       * gas/cfi/cfi-arm-1.s: Change usage of sp to ip in 'ldmea'.
       * gas/arm/arm-ldm-bad.s: New file.
       * gas/arm/arm-ldm-bad.d: Likewise.
       * gas/arm/arm-ldm-bad.l: Likewise.


commit 945c748ad5075d3d0e7d54e6258d8ab9bcf5fa36
Author: Kyrylo Tkachov <>
Date:   Mon Jun 30 17:28:56 2014 +0100

      [ARM][gas] ldm sp warnings

diff --git a/gas/config/tc-arm.c b/gas/config/tc-arm.c
index ce0532b..5755b4b 100644
--- a/gas/config/tc-arm.c
+++ b/gas/config/tc-arm.c
@@ -8130,6 +8130,15 @@ encode_ldmstm(int from_push_pop_mnem)

+  if (inst.instruction & LOAD_BIT
+      && ARM_CPU_HAS_FEATURE (cpu_variant, arm_ext_v7a))
+    {
+      if (range & (1 << REG_SP))
+        as_warn (_("usage of SP in register list is deprecated"));
+      else if (range & (1 << REG_PC) && range & (1 << REG_LR))
+        as_warn (_("usage of both LR and PC in register list is deprecated"));
+    }
     /* If PUSH/POP has only one register, then use the A2 encoding.  */
     one_reg = only_one_reg_in_list (range);
     if (from_push_pop_mnem && one_reg >= 0)
diff --git a/gas/testsuite/gas/arm/arm-ldm-bad.d b/gas/testsuite/gas/arm/arm-ldm-bad.d
new file mode 100644
index 0000000..8ce6a54
--- /dev/null
+++ b/gas/testsuite/gas/arm/arm-ldm-bad.d
@@ -0,0 +1,3 @@
+#name: ARM ldm/stm warnings
+#as: -march=armv7-a
+#error-output: arm-ldm-bad.l
diff --git a/gas/testsuite/gas/arm/arm-ldm-bad.l b/gas/testsuite/gas/arm/arm-ldm-bad.l
new file mode 100644
index 0000000..1609594
--- /dev/null
+++ b/gas/testsuite/gas/arm/arm-ldm-bad.l
@@ -0,0 +1,5 @@
+[^:]*: Assembler messages:
+[^:]*:4: Warning: usage of both LR and PC in register list is deprecated
+[^:]*:5: Warning: usage of both LR and PC in register list is deprecated
+[^:]*:6: Warning: usage of SP in register list is deprecated
+[^:]*:7: Warning: usage of SP in register list is deprecated
diff --git a/gas/testsuite/gas/arm/arm-ldm-bad.s b/gas/testsuite/gas/arm/arm-ldm-bad.s
new file mode 100644
index 0000000..d16cf5d
--- /dev/null
+++ b/gas/testsuite/gas/arm/arm-ldm-bad.s
@@ -0,0 +1,7 @@
+     .global entry
+     .text
+     ldm sp, {r4-r7,r11,lr,pc}
+     ldm sp!, {r4-r7,r11,lr,pc}
+     ldm r1, {r4-r7,sp}
+     ldm r1!, {r4-r7,sp}
diff --git a/gas/testsuite/gas/cfi/cfi-arm-1.s b/gas/testsuite/gas/cfi/cfi-arm-1.s
index d962442..481f4f2 100644
--- a/gas/testsuite/gas/cfi/cfi-arm-1.s
+++ b/gas/testsuite/gas/cfi/cfi-arm-1.s
@@ -23,7 +23,7 @@ foo:
        .cfi_offset r1,  -16
        .cfi_offset s1,  -20
        .cfi_offset d11, -48
-     ldmea   fp, {fp, sp, pc}
+     ldmea   fp, {fp, ip, pc}
        .size   foo, .-foo

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