[mips][micromips] Add pattern for JmpLink to TargetExternalSymbol

[abeserminji]

Summary

When matching MipsISD::JmpLink t9, TargetExternalSymbol:i32'memset'...
wrong JALR16_MM is selected. This patch adds missing pattern for JmpLink,
so that JAL instruction is selected.

[atanasyan]

LGTM

[sdardis]

lib/Target/Mips/MicroMipsInstrInfo.td

1454 ↗

(On Diff #169969)

This is in the wrong place. It should proceed the tail call patterns on line 1274.

test/CodeGen/Mips/micromips-target-external-symbol-reloc.ll

1 ↗

(On Diff #169969)

This test can be made better by declaring an external function f rather than memset as the memset intrinsic could be expanded inline by the MIPS backend in the future in any number of ways, e.g. lwm/swm in a loop for O3.

Another thing is that the test can be quicker by stopping after the isel expand pseudos pass and checking for the presence of JAL_MM, rather than assemblying an object then disassembling it. Another approach would be to extend test/CodeGen/Mips/llvm-ir/isel.ll for this case.

[abeserminji]

test/CodeGen/Mips/micromips-target-external-symbol-reloc.ll

1 ↗

(On Diff #169969)

Hello Simon, good to hear from you

I tried the solution you proposed before submitting this one, but it didn't work.
If I declare an external function, I don't get a call with JAL.
Then I found this very old post:
http://lists.llvm.org/pipermail/llvm-dev/2006-October/006973.html
So I guess if it still stands, it explains why I couldn't use external function for this test.

And for the second part of the comment, I will make these changes with new update.

[abeserminji]

Resolved some comments.

[sdardis]

LGTM. Just remember to upload the patches with context.

llvm/trunk/lib/Target/Mips/MicroMipsInstrInfo.td

 let AddedComplexity = 40 in
   def : MipsPat<(i32 (sextloadi16 addrRegImm:$a)),
                 (LH_MM addrRegImm:$a)>, ISA_MICROMIPS;
 
 
 def : MipsPat<(bswap GPR32:$rt), (ROTR_MM (WSBH_MM GPR32:$rt), 16)>,
       ISA_MICROMIPS;
 
+def : MipsPat<(MipsJmpLink (i32 texternalsym:$dst)),
+              (JAL_MM texternalsym:$dst)>, ISA_MICROMIPS32_NOT_MIPS32R6;
 def : MipsPat<(MipsTailCall (iPTR tglobaladdr:$dst)),
               (TAILCALL_MM tglobaladdr:$dst)>, ISA_MICROMIPS32_NOT_MIPS32R6;
 def : MipsPat<(MipsTailCall (iPTR texternalsym:$dst)),
               (TAILCALL_MM texternalsym:$dst)>, ISA_MICROMIPS32_NOT_MIPS32R6;
 
 defm : BrcondPats<GPR32, BEQ_MM, BEQ_MM, BNE_MM, SLT_MM, SLTu_MM, SLTi_MM,
                   SLTiu_MM, ZERO>, ISA_MICROMIPS32_NOT_MIPS32R6;
 

llvm/trunk/test/CodeGen/Mips/micromips-target-external-symbol-reloc.ll

+; RUN: llc -mtriple=mips-mti-linux-gnu -mcpu=mips32r2 -mattr=+micromips -stop-after=expand-isel-pseudos < %s | FileCheck %s
+
+; CHECK: JAL_MM
+; CHECK-NOT: JALR16_MM
+
+define dso_local void @foo(i32* nocapture %ar) local_unnamed_addr {
+entry:
+  %0 = bitcast i32* %ar to i8*
+  tail call void @llvm.memset.p0i8.i32(i8* align 4 %0, i8 0, i32 100, i1 false)
+  ret void
+}
+
+declare void @llvm.memset.p0i8.i32(i8* nocapture writeonly, i8, i32, i1)