Re: [Patch, ARM/Thumb1]Add a Thumb1 insn pattern to legalize the instruction that moves pc to low register

[Ramana Radhakrishnan <ramana dot gcc at googlemail dot com>]

On Fri, Jan 9, 2015 at 7:43 AM, Terry Guo <terry.guo@arm.com> wrote:
>
>
>> -----Original Message-----
>> From: Richard Earnshaw
>> Sent: Monday, December 08, 2014 7:31 PM
>> To: Terry Guo; gcc-patches@gcc.gnu.org
>> Cc: Ramana Radhakrishnan
>> Subject: Re: [Patch, ARM/Thumb1]Add a Thumb1 insn pattern to legalize the
>> instruction that moves pc to low register
>>
>> On 08/12/14 08:24, Terry Guo wrote:
>> > Hi there,
>> >
>> > When compile below simple code:
>> >
>> > terguo01@terry-pc01:mtpcs-frame$ cat test.c int main(void) {
>> >     return 0;
>> > }
>> >
>> > I got ICE with option -mtpcs-leaf-frame (no error if remove this
> option).
>> >
>> > terguo01@terry-pc01:mtpcs-frame$
>> > /work/terguo01/tools/gcc-arm-none-eabi-5_0-2014q4/bin/arm-none-eabi-
>> gc
>> > c -mtpcs-leaf-frame test.c -c -mcpu=cortex-m0plus -mthumb -da
>> > test.c: In function 'main':
>> > test.c:4:1: error: unrecognizable insn:
>> >  }
>> >  ^
>> > (insn 20 19 21 (set (reg:SI 2 r2)
>> >         (reg:SI 15 pc)) test.c:2 -1
>> >      (nil))
>> > test.c:4:1: internal compiler error: in extract_insn, at recog.c:2327
>> > Please submit a full bug report, with preprocessed source if
>> > appropriate.
>> > See http://gcc.gnu.org/bugs.html\ for instructions.
>> >
>> > This RTL is generated in function thumb1_expand_prologue. The expected
>> > insn pattern is thumb1_movsi_insn in thumb1.md. And instruction like
>> "mov r2, pc"
>> > is a legal instruction. Because gcc returns NO_REG for PC register, so
>> > no valid pattern to match instruction that move pc to low register.
>> > This patch intends to add a new insn pattern to legalize such thing.
>> >
>> > Tested with GCC regression test. No regression. Is it OK to trunk?
>> >
>> > BR,
>> > Terry
>> >
>> > 2014-12-08  Terry Guo  terry.guo@arm.com
>> >
>> >      * config/arm/predicates.md (pc_register): New to match PC register.
>> >      * config/arm/thumb1.md (*thumb1_movpc_insn): New insn pattern.
>> >
>> > gcc/testsuite/ChangeLog:
>> > 2014-12-08  Terry Guo  terry.guo@arm.com
>> >
>> >      * gcc.target/arm/thumb1-mov-pc.c: New test.
>> >
>> >
>> > thumb1-move-pc-v1.txt
>> >
>> >
>> > diff --git a/gcc/config/arm/predicates.md
>> > b/gcc/config/arm/predicates.md index 032808c..c5ef5ed 100644
>> > --- a/gcc/config/arm/predicates.md
>> > +++ b/gcc/config/arm/predicates.md
>> > @@ -361,6 +361,10 @@
>> >    (and (match_code "smin,smax,umin,umax")
>> >         (match_test "mode == GET_MODE (op)")))
>> >
>> > +(define_special_predicate "pc_register"
>> > +  (and (match_code "reg")
>> > +       (match_test "REGNO (op) == PC_REGNUM")))
>> > +
>> >  (define_special_predicate "cc_register"
>> >    (and (match_code "reg")
>> >         (and (match_test "REGNO (op) == CC_REGNUM") diff --git
>> > a/gcc/config/arm/thumb1.md b/gcc/config/arm/thumb1.md index
>> > ddedc39..8e6057c 100644
>> > --- a/gcc/config/arm/thumb1.md
>> > +++ b/gcc/config/arm/thumb1.md
>> > @@ -1780,6 +1780,16 @@
>> >    "
>> >  )
>> >
>> > +(define_insn "*thumb1_movpc_insn"
>> > +  [(set (match_operand:SI 0 "low_register_operand")
>>
>> This needs constraints.
>>
>
> The constraint is used now. Is this one OK?


This is OK now.

Ramana
>
> BR,
> Terry
>
> 2015-01-09  Terry Guo  terry.guo@arm.com
>
>          * config/arm/thumb1.md (*thumb1_movpc_insn): New insn pattern.