[AMDGPU] Produce madak and madmk from the two-address pass

[rampitec]

Summary

These two instructions are normally selected, but when the
two address pass converts mac into mad we end up with the
mad where we could have one of these.

[arsenm]

I don't think this is the right place for this. This is converting a two address instruction into another two address instruction. Why wasn't this matched to a v_madak originally?

[arsenm]

This looks like it is undoing the specific handling for 2 uses done in FoldImmediate. This also probably should be handled there, and specifically for 2 uses. Also needs a test with 3+ uses, where it probably still shouldn't be folded.

[rampitec]

In D37389#859395, @arsenm wrote:

I don't think this is the right place for this. This is converting a two address instruction into another two address instruction. Why wasn't this matched to a v_madak originally?

It was selected as mac, and mac is preferable over mad or madmk.

[rampitec]

In D37389#859399, @arsenm wrote:

This looks like it is undoing the specific handling for 2 uses done in FoldImmediate. This also probably should be handled there, and specifically for 2 uses. Also needs a test with 3+ uses, where it probably still shouldn't be folded.

There is no point in the folding. Both mad and madak use 64 bit, both use constant bus. With folding we also using one extra register and plus madak/madmk are VOP2, so preferable.

[rampitec]

In D37389#859432, @rampitec wrote:

In D37389#859395, @arsenm wrote:

I don't think this is the right place for this. This is converting a two address instruction into another two address instruction. Why wasn't this matched to a v_madak originally?

It was selected as mac, and mac is preferable over mad or madmk.

In fact I do not see how madak is different from mad in the respect of two/three address. It really worth nothing that one of the register operands can be also folded into the instruction as immediate. If we would produce mad here and fold immediate later the result would be same, just more work. The pass needs to simplify operands and we do it. For the selection part I also do not see how could it efficiently deal with register pressure issues, it is just too early.

[arsenm]

In D37389#861163, @rampitec wrote:

In D37389#859432, @rampitec wrote:

In D37389#859395, @arsenm wrote:

I don't think this is the right place for this. This is converting a two address instruction into another two address instruction. Why wasn't this matched to a v_madak originally?

It was selected as mac, and mac is preferable over mad or madmk.

In fact I do not see how madak is different from mad in the respect of two/three address. It really worth nothing that one of the register operands can be also folded into the instruction as immediate. If we would produce mad here and fold immediate later the result would be same, just more work. The pass needs to simplify operands and we do it. For the selection part I also do not see how could it efficiently deal with register pressure issues, it is just too early.

OK, I was thinking of s_mulk_i32/s_addk_i32 which is an inplace update of the register.

test/CodeGen/AMDGPU/madak.ll

40

Should add a test with 3 uses. We should consider not doing it for > 2 uses if optsize

[rampitec]

test/CodeGen/AMDGPU/madak.ll

40

We shall always use madak/madmk instead of v_mad_f32. Size of the instruction is the same: mad is VOP3, madak/madmk are VOP2 + literal. I.e. 64 bit VOP3 vs 32 bit VOP2 + 32 bit literal.

At the same time we can save a register for the literal and move into that register. So even for the optsize we shall prefer these.

[arsenm]

lib/Target/AMDGPU/SIInstrInfo.cpp

2092

You don't need the isFullCopy check. COPY can't be used to materialize an immediate. Def->isMoveImm() instead of the separate opcode checks

2137

Braces

2138

What if this is an f16 mac?

[rampitec]

lib/Target/AMDGPU/SIInstrInfo.cpp

2092

isMoveImm() will catch cmov, so will not work. isFullCopy removed.

2138

"if (!IsF16 ..." on line 2132.

[arsenm]

lib/Target/AMDGPU/SIInstrInfo.cpp

2092

It won't catch cmov (I assume you mean s_cmov_b32, which we also don't emit).

2138

But we can handle f16 here as well, so might as well

[rampitec]

lib/Target/AMDGPU/SIInstrInfo.cpp

2092

It doesn't matter we do not produce it right now. Until it is marked as move imm I cannot use it, that is a time bomb. In fact I could remove flag from S_CMOV_B*. Objections?

[rampitec]

Added f16 case.

[arsenm]

LGTM with the minor cleanup

lib/Target/AMDGPU/SIInstrInfo.cpp

2139

Assign the opcode to a variable instead of repeating this 3 places

[rampitec]

In D37389#866644, @arsenm wrote:

LGTM with the minor cleanup

We only know what to assign inside each if statement.

lib/Target/AMDGPU/SIInstrInfo.cpp

if (isFLAT(MIb))
       return checkInstOffsetsDoNotOverlap(MIa, MIb);
 
     return false;
   }
 
   return false;
 }
 
+static int64_t getFoldableImm(const MachineOperand* MO) {
+  if (!MO->isReg())
+    return false;
+  const MachineFunction *MF = MO->getParent()->getParent()->getParent();
+  const MachineRegisterInfo &MRI = MF->getRegInfo();
+  auto Def = MRI.getUniqueVRegDef(MO->getReg());
+  if (Def && (Def->getOpcode() == AMDGPU::S_MOV_B32 ||
+              Def->getOpcode() == AMDGPU::V_MOV_B32_e32) &&
+     Def->getOperand(1).isImm())
+    return Def->getOperand(1).getImm();
+  return AMDGPU::NoRegister;
+}
+
 MachineInstr *SIInstrInfo::convertToThreeAddress(MachineFunction::iterator &MBB,
                                                  MachineInstr &MI,
                                                  LiveVariables *LV) const {
   bool IsF16 = false;
 
   switch (MI.getOpcode()) {
   default:
     return nullptr;
const MachineOperand *Src0Mods =
     getNamedOperand(MI, AMDGPU::OpName::src0_modifiers);
   const MachineOperand *Src1 = getNamedOperand(MI, AMDGPU::OpName::src1);
   const MachineOperand *Src1Mods =
     getNamedOperand(MI, AMDGPU::OpName::src1_modifiers);
   const MachineOperand *Src2 = getNamedOperand(MI, AMDGPU::OpName::src2);
   const MachineOperand *Clamp = getNamedOperand(MI, AMDGPU::OpName::clamp);
   const MachineOperand *Omod = getNamedOperand(MI, AMDGPU::OpName::omod);
 
+  if (!IsF16 && !Src0Mods && !Src1Mods && !Clamp && !Omod) {
+    if (auto Imm = getFoldableImm(Src2)) {
+      return BuildMI(*MBB, MI, MI.getDebugLoc(), get(AMDGPU::V_MADAK_F32))
+               .add(*Dst)
+               .add(*Src0)
+               .add(*Src1)
+               .addImm(Imm);
+    }
+    if (auto Imm = getFoldableImm(Src1)) {
+      return BuildMI(*MBB, MI, MI.getDebugLoc(), get(AMDGPU::V_MADMK_F32))
+               .add(*Dst)
+               .add(*Src0)
+               .addImm(Imm)
+               .add(*Src2);
+    }
+    if (auto Imm = getFoldableImm(Src0)) {
+      if (isOperandLegal(MI, AMDGPU::getNamedOperandIdx(AMDGPU::V_MADMK_F32,
+                           AMDGPU::OpName::src0), Src1))
+        return BuildMI(*MBB, MI, MI.getDebugLoc(), get(AMDGPU::V_MADMK_F32))
+                 .add(*Dst)
+                 .add(*Src1)
+                 .addImm(Imm)
+                 .add(*Src2);
+    }
+  }
+
   return BuildMI(*MBB, MI, MI.getDebugLoc(),
                  get(IsF16 ? AMDGPU::V_MAD_F16 : AMDGPU::V_MAD_F32))
       .add(*Dst)
       .addImm(Src0Mods ? Src0Mods->getImm() : 0)
       .add(*Src0)
       .addImm(Src1Mods ? Src1Mods->getImm() : 0)
       .add(*Src1)
       .addImm(0) // Src mods

test/CodeGen/AMDGPU/madak.ll

 ; optimization and if we fold the immediate multiple times, we'll undo
 ; it.
 
 ; GCN-LABEL: {{^}}madak_2_use_f32:
 ; GCN-DAG: buffer_load_dword [[VA:v[0-9]+]], {{v\[[0-9]+:[0-9]+\]}}, {{s\[[0-9]+:[0-9]+\]}}, 0 addr64{{$}}
 ; GCN-DAG: buffer_load_dword [[VB:v[0-9]+]], {{v\[[0-9]+:[0-9]+\]}}, {{s\[[0-9]+:[0-9]+\]}}, 0 addr64 offset:4
 ; GCN-DAG: buffer_load_dword [[VC:v[0-9]+]], {{v\[[0-9]+:[0-9]+\]}}, {{s\[[0-9]+:[0-9]+\]}}, 0 addr64 offset:8
 ; GCN-DAG: v_mov_b32_e32 [[VK:v[0-9]+]], 0x41200000
-; GCN-DAG: v_mad_f32 {{v[0-9]+}}, [[VA]], [[VB]], [[VK]]
+; GCN-DAG: v_madak_f32 {{v[0-9]+}}, [[VA]], [[VB]], 0x41200000
 ; GCN-DAG: v_mac_f32_e32 [[VK]], [[VA]], [[VC]]
 ; GCN: s_endpgm
 define amdgpu_kernel void @madak_2_use_f32(float addrspace(1)* noalias %out, float addrspace(1)* noalias %in) nounwind {
   %tid = tail call i32 @llvm.amdgcn.workitem.id.x() nounwind readnone
 
   %in.gep.0 = getelementptr float, float addrspace(1)* %in, i32 %tid
   %in.gep.1 = getelementptr float, float addrspace(1)* %in.gep.0, i32 1
   %in.gep.2 = getelementptr float, float addrspace(1)* %in.gep.0, i32 2
 
   %out.gep.0 = getelementptr float, float addrspace(1)* %out, i32 %tid
   %out.gep.1 = getelementptr float, float addrspace(1)* %in.gep.0, i32 1

test/CodeGen/AMDGPU/twoaddr-mad.mir

+# RUN: llc -march=amdgcn %s -run-pass twoaddressinstruction -verify-machineinstrs -o - | FileCheck -check-prefix=GCN %s
+
+# GCN-LABEL: name: test_madmk_reg_imm
+# GCN: V_MADMK_F32 killed %0.sub0, 1078523331, killed %1, implicit %exec
+---
+name:            test_madmk_reg_imm
+registers:
+  - { id: 0, class: vreg_64 }
+  - { id: 1, class: vgpr_32 }
+  - { id: 2, class: vgpr_32 }
+  - { id: 3, class: vgpr_32 }
+body:             |
+  bb.0:
+
+    %0 = IMPLICIT_DEF
+    %1 = COPY %0.sub1
+    %2 = V_MOV_B32_e32 1078523331, implicit %exec
+    %3 = V_MAC_F32_e32 killed %0.sub0, %2, killed %1, implicit %exec
+
+...
+
+# GCN-LABEL: name: test_madmk_imm_reg
+# GCN: V_MADMK_F32 killed %0.sub0, 1078523331, killed %1, implicit %exec
+---
+name:            test_madmk_imm_reg
+registers:
+  - { id: 0, class: vreg_64 }
+  - { id: 1, class: vgpr_32 }
+  - { id: 2, class: vgpr_32 }
+  - { id: 3, class: vgpr_32 }
+body:             |
+  bb.0:
+
+    %0 = IMPLICIT_DEF
+    %1 = COPY %0.sub1
+    %2 = V_MOV_B32_e32 1078523331, implicit %exec
+    %3 = V_MAC_F32_e32 %2, killed %0.sub0, killed %1, implicit %exec
+
+...
+
+# GCN-LABEL: name: test_madak
+# GCN: V_MADAK_F32 killed %0.sub0, %0.sub1, 1078523331, implicit %exec
+---
+name:            test_madak
+registers:
+  - { id: 0, class: vreg_64 }
+  - { id: 1, class: vgpr_32 }
+  - { id: 2, class: vgpr_32 }
+body:             |
+  bb.0:
+
+    %0 = IMPLICIT_DEF
+    %1 = V_MOV_B32_e32 1078523331, implicit %exec
+    %2 = V_MAC_F32_e32 killed %0.sub0, %0.sub1, %1, implicit %exec
+
+...

test/CodeGen/AMDGPU/v_madak_f16.ll

entry:
   %t.val = fmul half %a.val, %b.val
   %r.val = fadd half %t.val, 10.0
 
   store half %r.val, half addrspace(1)* %r
   ret void
 }
 
 ; GCN-LABEL: {{^}}madak_f16_use_2
-; SI:  v_mad_f32 v{{[0-9]+}}, v{{[0-9]+}}, v{{[0-9]+}}, v{{[0-9]+}}
+; SI:  v_madak_f32 v{{[0-9]+}}, v{{[0-9]+}}, v{{[0-9]+}}, 0x41200000
 ; SI:  v_mac_f32_e32 v{{[0-9]+}}, v{{[0-9]+}}, v{{[0-9]+}}
 ; VI:  v_mad_f16 v{{[0-9]+}}, v{{[0-9]+}}, v{{[0-9]+}}, v{{[0-9]+}}
 ; VI:  v_mac_f16_e32 v{{[0-9]+}}, v{{[0-9]+}}, v{{[0-9]+}}
 ; GCN: s_endpgm
 define amdgpu_kernel void @madak_f16_use_2(
     half addrspace(1)* %r0,
     half addrspace(1)* %r1,
     half addrspace(1)* %a,