[PATCH] Fix bug in Sema::ActOnGCCAsmStmt (PR21270)

[Akira Hatanaka]

ping

On Mon, Nov 3, 2014 at 1:07 PM, Akira Hatanaka <ahatanak at gmail.com> wrote:

> ping
>
> On Wed, Oct 15, 2014 at 9:27 AM, Akira Hatanaka <ahatanak at gmail.com>
> wrote:
>
>> There were mistakes in my previous email. The correct mapping should be
>> like this:
>>
>> %0 => "+r" (one) => ConstraintIdx = 0
>> %1 => "+r" (two) => ConstraintIdx = 1
>> %2 => "r" (three) => ConstraintIdx = 2
>> %3 => "+r" (one) => ConstraintIdx = 0
>> %4 => "+r" (two) => ConstraintIdx = 1
>>
>> On Wed, Oct 15, 2014 at 8:36 AM, Akira Hatanaka <ahatanak at gmail.com>
>> wrote:
>>
>>> The attached patch fixes a bug in Sema::ActOnGCCAsmStmt where it wasn't
>>> computing the corresponding ConstraintIdx from an operand number correctly
>>> when there were constraints with the '+' modifier.
>>>
>>> For example, when the following inline-asm statement is compiled,
>>>
>>> void g2(int one, int two, int three) {
>>>   asm volatile ("%0 %1 %2 %3 %4" : "+r" (one), "+r"(two) : "r"(three));
>>> }
>>>
>>> the existing code maps the operand number in the assembly template to
>>> ConstraintIdx in the following way:
>>>
>>> %0 => "+r" (one) => ConstraintIdx = 0
>>> %1 => "+r" (one) => ConstraintIdx = 0
>>> %2 => "+r" (two) => ConstraintIdx = 1
>>> %3 => "+r" (two) => ConstraintIdx = 1
>>> %4 => "+r" (three) => ConstraintIdx = 2
>>>
>>> The correct mapping should be like this:
>>>
>>> %0 => "+r" (one) => ConstraintIdx = 0
>>> %1 => "+r" (two) => ConstraintIdx = 1
>>> %3 => "+r" (three) => ConstraintIdx = 2
>>> %4 => "+r" (one) => ConstraintIdx = 0
>>> %5 => "+r" (two) => ConstraintIdx = 1
>>>
>>> I couldn't find the rule documented anywhere in the link below, but
>>> judging from the code I see in CodeGenFunction::EmitAsmStmt and the IR
>>> clang generates, I believe this is the correct way to find the
>>> corresponding constraint.
>>>
>>> https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
>>>
>>> This is the IR generated:
>>>
>>> %1 = tail call { i32, i32 } asm sideeffect "$0 $1 $2 $3 $4",
>>> "=r,=r,r,0,1"(i32 %three, i32 %one, i32 %two)
>>>
>>
>>
>
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