[GlobalISel][X86] Support G_BRCOND operation.

[igorb]

Summary

Support G_BRCOND operation. For now don't try to fold cmp/trunc instructions.

[guyblank]

lgtm

[igorb]

• rebase

lib/Target/X86/X86InstructionSelector.cpp

private:
   bool selectUnmergeValues(MachineInstr &I, MachineRegisterInfo &MRI,
                            MachineFunction &MF) const;
   bool selectMergeValues(MachineInstr &I, MachineRegisterInfo &MRI,
                          MachineFunction &MF) const;
   bool selectInsert(MachineInstr &I, MachineRegisterInfo &MRI,
                     MachineFunction &MF) const;
   bool selectExtract(MachineInstr &I, MachineRegisterInfo &MRI,
                      MachineFunction &MF) const;
+  bool selectCondBranch(MachineInstr &I, MachineRegisterInfo &MRI,
+                        MachineFunction &MF) const;
 
   // emit insert subreg instruction and insert it before MachineInstr &I
   bool emitInsertSubreg(unsigned DstReg, unsigned SrcReg, MachineInstr &I,
                         MachineRegisterInfo &MRI, MachineFunction &MF) const;
   // emit extract subreg instruction and insert it before MachineInstr &I
   bool emitExtractSubreg(unsigned DstReg, unsigned SrcReg, MachineInstr &I,
                          MachineRegisterInfo &MRI, MachineFunction &MF) const;
 
bool X86InstructionSelector::select(MachineInstr &I) const {
   if (selectUnmergeValues(I, MRI, MF))
     return true;
   if (selectMergeValues(I, MRI, MF))
     return true;
   if (selectExtract(I, MRI, MF))
     return true;
   if (selectInsert(I, MRI, MF))
     return true;
+  if (selectCondBranch(I, MRI, MF))
+    return true;
 
   return false;
 }
 
 unsigned X86InstructionSelector::getLoadStoreOp(LLT &Ty, const RegisterBank &RB,
                                                 unsigned Opc,
                                                 uint64_t Alignment) const {
   bool Isload = (Opc == TargetOpcode::G_LOAD);
MachineInstr &CopyInst = *BuildMI(*I.getParent(), I, I.getDebugLoc(),
                                 .addReg(DefReg);
 
   if (!select(CopyInst))
     return false;
 
   I.eraseFromParent();
   return true;
 }
+
+bool X86InstructionSelector::selectCondBranch(MachineInstr &I,
+                                              MachineRegisterInfo &MRI,
+                                              MachineFunction &MF) const {
+  if (I.getOpcode() != TargetOpcode::G_BRCOND)
+    return false;
+
+  const unsigned CondReg = I.getOperand(0).getReg();
+  MachineBasicBlock *DestMBB = I.getOperand(1).getMBB();
+
+  MachineInstr &TestInst =
+      *BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(X86::TEST8ri))
+           .addReg(CondReg)
+           .addImm(1);
+  BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(X86::JNE_1))
+      .addMBB(DestMBB);
+
+  constrainSelectedInstRegOperands(TestInst, TII, TRI, RBI);
+
+  I.eraseFromParent();
+  return true;
+}
+
 InstructionSelector *
 llvm::createX86InstructionSelector(const X86TargetMachine &TM,
                                    X86Subtarget &Subtarget,
                                    X86RegisterBankInfo &RBI) {
   return new X86InstructionSelector(TM, Subtarget, RBI);
 }

lib/Target/X86/X86LegalizerInfo.cpp

void X86LegalizerInfo::setLegalizerInfo32bit() {
   setAction({G_GLOBAL_VALUE, p0}, Legal);
 
   setAction({G_GEP, p0}, Legal);
   setAction({G_GEP, 1, s32}, Legal);
 
   for (auto Ty : {s1, s8, s16})
     setAction({G_GEP, 1, Ty}, WidenScalar);
 
+  // Control-flow
+  setAction({G_BRCOND, s1}, Legal);
+
   // Constants
   for (auto Ty : {s8, s16, s32, p0})
     setAction({TargetOpcode::G_CONSTANT, Ty}, Legal);
 
   setAction({TargetOpcode::G_CONSTANT, s1}, WidenScalar);
   setAction({TargetOpcode::G_CONSTANT, s64}, NarrowScalar);
 
   // Extensions
void X86LegalizerInfo::setLegalizerInfo64bit() {
 
   setAction({G_GEP, p0}, Legal);
   setAction({G_GEP, 1, s32}, Legal);
   setAction({G_GEP, 1, s64}, Legal);
 
   for (auto Ty : {s1, s8, s16})
     setAction({G_GEP, 1, Ty}, WidenScalar);
 
+  // Control-flow
+  setAction({G_BRCOND, s1}, Legal);
+
   // Constants
   for (auto Ty : {s8, s16, s32, s64, p0})
     setAction({TargetOpcode::G_CONSTANT, Ty}, Legal);
 
   setAction({TargetOpcode::G_CONSTANT, s1}, WidenScalar);
 
   // Extensions
   for (auto Ty : {s8, s16, s32, s64}) {

test/CodeGen/X86/GlobalISel/brcond.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=x86_64-linux-gnu    -global-isel -verify-machineinstrs %s -o - | FileCheck %s --check-prefix=CHECK --check-prefix=X64
+; RUN: llc -mtriple=i386-linux-gnu      -global-isel -verify-machineinstrs %s -o - | FileCheck %s --check-prefix=CHECK --check-prefix=X32
+
+define i32 @test_1(i32 %a, i32 %b, i32 %tValue, i32 %fValue) {
+; X64-LABEL: test_1:
+; X64:       # BB#0: # %entry
+; X64-NEXT:    cmpl %esi, %edi
+; X64-NEXT:    setl %al
+; X64-NEXT:    testb $1, %al
+; X64-NEXT:    je .LBB0_2
+; X64-NEXT:  # BB#1: # %if.then
+; X64-NEXT:    movl %edx, -{{[0-9]+}}(%rsp)
+; X64-NEXT:    movl -{{[0-9]+}}(%rsp), %eax
+; X64-NEXT:    retq
+; X64-NEXT:  .LBB0_2: # %if.else
+; X64-NEXT:    movl %ecx, -{{[0-9]+}}(%rsp)
+; X64-NEXT:    movl -{{[0-9]+}}(%rsp), %eax
+; X64-NEXT:    retq
+;
+; X32-LABEL: test_1:
+; X32:       # BB#0: # %entry
+; X32-NEXT:    pushl %eax
+; X32-NEXT:  .Lcfi0:
+; X32-NEXT:    .cfi_def_cfa_offset 8
+; X32-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X32-NEXT:    cmpl %eax, {{[0-9]+}}(%esp)
+; X32-NEXT:    setl %al
+; X32-NEXT:    testb $1, %al
+; X32-NEXT:    je .LBB0_2
+; X32-NEXT:  # BB#1: # %if.then
+; X32-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X32-NEXT:    jmp .LBB0_3
+; X32-NEXT:  .LBB0_2: # %if.else
+; X32-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X32-NEXT:  .LBB0_3: # %return
+; X32-NEXT:    movl %eax, (%esp)
+; X32-NEXT:    movl (%esp), %eax
+; X32-NEXT:    popl %ecx
+; X32-NEXT:    retl
+entry:
+  %retval = alloca i32, align 4
+  %cmp = icmp slt i32 %a, %b
+  br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+  store i32 %tValue, i32* %retval, align 4
+  br label %return
+
+if.else:
+  store i32 %fValue, i32* %retval, align 4
+  br label %return
+
+return:
+  %0 = load i32, i32* %retval, align 4
+  ret i32 %0
+}
+
+define i32 @test_2(i32 %a) {
+; X64-LABEL: test_2:
+; X64:       # BB#0: # %entry
+; X64-NEXT:    testb $1, %dil
+; X64-NEXT:    je .LBB1_2
+; X64-NEXT:  # BB#1: # %if.then
+; X64-NEXT:    xorl %eax, %eax
+; X64-NEXT:    retq
+; X64-NEXT:  .LBB1_2: # %if.else
+; X64-NEXT:    movl $1, %eax
+; X64-NEXT:    retq
+;
+; X32-LABEL: test_2:
+; X32:       # BB#0: # %entry
+; X32-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X32-NEXT:    testb $1, %al
+; X32-NEXT:    je .LBB1_2
+; X32-NEXT:  # BB#1: # %if.then
+; X32-NEXT:    xorl %eax, %eax
+; X32-NEXT:    retl
+; X32-NEXT:  .LBB1_2: # %if.else
+; X32-NEXT:    movl $1, %eax
+; X32-NEXT:    retl
+entry:
+  %cmp = trunc i32 %a to i1
+  br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+  ret i32 0
+if.else:
+  ret i32 1
+}
+

test/CodeGen/X86/GlobalISel/legalize-brcond.mir

+# RUN: llc -mtriple=x86_64-linux-gnu -global-isel -run-pass=legalizer %s -o - | FileCheck %s --check-prefix=ALL --check-prefix=X64
+# RUN: llc -mtriple=i386-linux-gnu   -global-isel -run-pass=legalizer %s -o - | FileCheck %s --check-prefix=ALL --check-prefix=X32
+
+--- |
+
+  define i32 @test(i32 %a) {
+  entry:
+    %cmp = trunc i32 %a to i1
+    br i1 %cmp, label %if.then, label %if.else
+
+  if.then:                                          ; preds = %entry
+    ret i32 0
+
+  if.else:                                          ; preds = %entry
+    ret i32 1
+  }
+...
+---
+name:            test
+# ALL-LABEL: name:  test
+alignment:       4
+legalized:       false
+regBankSelected: false
+registers:
+  - { id: 0, class: _, preferred-register: '' }
+  - { id: 1, class: _, preferred-register: '' }
+  - { id: 2, class: _, preferred-register: '' }
+  - { id: 3, class: _, preferred-register: '' }
+# ALL:         %1(s1) = G_TRUNC %0(s32)
+# ALL-NEXT:    G_BRCOND %1(s1), %[[TRUE:bb.[0-9]+.if.then]]
+# ALL-NEXT:    G_BR %[[FALSE:bb.[0-9]+.if.else]]
+# ALL:       [[TRUE]]:
+# ALL-NEXT:    %eax = COPY %2(s32)
+# ALL-NEXT:    RET 0, implicit %eax
+# ALL:       [[FALSE]]:
+# ALL-NEXT:    %eax = COPY %3(s32)
+# ALL-NEXT:    RET 0, implicit %eax
+body:             |
+  bb.1.entry:
+    successors: %bb.2.if.then(0x40000000), %bb.3.if.else(0x40000000)
+    liveins: %edi
+
+    %0(s32) = COPY %edi
+    %2(s32) = G_CONSTANT i32 0
+    %3(s32) = G_CONSTANT i32 1
+    %1(s1) = G_TRUNC %0(s32)
+    G_BRCOND %1(s1), %bb.2.if.then
+    G_BR %bb.3.if.else
+
+  bb.2.if.then:
+    %eax = COPY %2(s32)
+    RET 0, implicit %eax
+
+  bb.3.if.else:
+    %eax = COPY %3(s32)
+    RET 0, implicit %eax
+
+...

test/CodeGen/X86/GlobalISel/select-brcond.mir

+# RUN: llc -mtriple=x86_64-linux-gnu    -global-isel -run-pass=instruction-select -verify-machineinstrs %s -o - | FileCheck %s --check-prefix=CHECK --check-prefix=X64
+# RUN: llc -mtriple=i386-linux-gnu      -global-isel -run-pass=instruction-select -verify-machineinstrs %s -o - | FileCheck %s --check-prefix=CHECK --check-prefix=X32
+
+--- |
+
+  define i32 @test(i32 %a) {
+  entry:
+    %cmp = trunc i32 %a to i1
+    br i1 %cmp, label %true, label %false
+
+  true:                                             ; preds = %entry
+    ret i32 0
+
+  false:                                            ; preds = %entry
+    ret i32 1
+  }
+
+...
+---
+name:            test
+# CHECK-LABEL: name:  test
+alignment:       4
+legalized:       true
+regBankSelected: true
+# X64:        registers:
+# X64-NEXT:     - { id: 0, class: gr32, preferred-register: '' }
+# X64-NEXT:     - { id: 1, class: gr8, preferred-register: '' }
+# X64-NEXT:     - { id: 2, class: gr32, preferred-register: '' }
+# X64-NEXT:     - { id: 3, class: gr32, preferred-register: '' }
+#
+# X32:        registers:
+# X32-NEXT:     - { id: 0, class: gr32_abcd, preferred-register: '' }
+# X32-NEXT:     - { id: 1, class: gr8, preferred-register: '' }
+# X32-NEXT:     - { id: 2, class: gr32, preferred-register: '' }
+# X32-NEXT:     - { id: 3, class: gr32, preferred-register: '' }
+registers:
+  - { id: 0, class: gpr, preferred-register: '' }
+  - { id: 1, class: gpr, preferred-register: '' }
+  - { id: 2, class: gpr, preferred-register: '' }
+  - { id: 3, class: gpr, preferred-register: '' }
+# CHECK:         %0 = COPY %edi
+# CHECK-NEXT:    %2 = MOV32r0 implicit-def %eflags
+# CHECK-NEXT:    %3 = MOV32ri 1
+# CHECK-NEXT:    %1 = COPY %0.sub_8bit
+# CHECK-NEXT:    TEST8ri %1, 1, implicit-def %eflags
+# CHECK-NEXT:    JNE_1 %[[TRUE:bb.[0-9].true]], implicit %eflags
+# CHECK-NEXT:    JMP_1 %[[FALSE:bb.[0-9].false]] 
+# CHECK:      [[TRUE]]:
+# CHECK-NEXT:    %eax = COPY %2
+# CHECK-NEXT:    RET 0, implicit %eax
+# CHECK:      [[FALSE]]:
+# CHECK-NEXT:    %eax = COPY %3
+# CHECK-NEXT:    RET 0, implicit %eax
+
+
+body:             |
+  bb.1.entry:
+    successors: %bb.2.true(0x40000000), %bb.3.false(0x40000000)
+    liveins: %edi
+
+    %0(s32) = COPY %edi
+    %2(s32) = G_CONSTANT i32 0
+    %3(s32) = G_CONSTANT i32 1
+    %1(s1) = G_TRUNC %0(s32)
+    G_BRCOND %1(s1), %bb.2.true
+    G_BR %bb.3.false
+
+  bb.2.true:
+    %eax = COPY %2(s32)
+    RET 0, implicit %eax
+
+  bb.3.false:
+    %eax = COPY %3(s32)
+    RET 0, implicit %eax
+
+...