[x86][inline-asm] Generate call instruction in pic

We encounter a inline bug in generating call, hard to fix.

I want to ask some questions here.

1st Does the IR generate from FE is wrong ?

PLS refer t.ll line3, it use “m” constrain for call operand “void (…) @sincos”. I think the right IR should be (“m” + “void (…)* @sincos”) or (“m” + “void (…)* @sincos_ptr”)

related patch in FE https://reviews.llvm.org/D107523

2nd How we fix it in Back End ?

I find it is hard to fix in BE, because the current arch of inline_asm let us hard to match the variable to its instruction.

I create a unbeautiful patch at BE too https://reviews.llvm.org/D108024

The following code will generate one more time load for “sincos” with cmd “clang -fasm-blocks t.c -fpic -S -emit-llvm” + “llc t.ll”


1 extern void sincos ();

2 void foo (){

3 __asm{

4 call sincos

5 ret };

6 }


1 define void @foo() #0 {

2 entry:

3 call void asm sideeffect inteldialect “call qword ptr ${0:P}\0A\09ret”, "m,~{dirflag},~{fpsr},~{flags}"(void (…) @sincos) #2, !srcloc !5

4 ret void

5 }


1 movq sincos@GOTPCREL(%rip), %rax // now the rax has been the function address “sincos”

2 #APP

3 callq *(%rax) // the call should directly read the %rax, should not “load” it again, it should be “callq *%rax” or better code “call sincos@plt”

4 retq



Thank you!