[GlobalISel][x86] Add the support for G_FPTRUNC

[aivchenk]

Summary

The instruction selection is automatically handled by tablegen

[igorb]

LGTM

lib/Target/X86/X86LegalizerInfo.cpp

for (unsigned BinOp : {G_ADD, G_SUB})
     for (auto Ty : {v16s8, v8s16, v4s32, v2s64})
       setAction({BinOp, Ty}, Legal);
 
   setAction({G_MUL, v8s16}, Legal);
 
   setAction({G_FPEXT, s64}, Legal);
   setAction({G_FPEXT, 1, s32}, Legal);
 
+  setAction({G_FPTRUNC, s32}, Legal);
+  setAction({G_FPTRUNC, 1, s64}, Legal);
+
   // Constants
   setAction({TargetOpcode::G_FCONSTANT, s64}, Legal);
 
   // Merge/Unmerge
   for (const auto &Ty :
        {v16s8, v32s8, v8s16, v16s16, v4s32, v8s32, v2s64, v4s64}) {
     setAction({G_MERGE_VALUES, Ty}, Legal);
     setAction({G_UNMERGE_VALUES, 1, Ty}, Legal);

lib/Target/X86/X86RegisterBankInfo.cpp

default:
     break;
   }
 
   unsigned NumOperands = MI.getNumOperands();
   SmallVector<PartialMappingIdx, 4> OpRegBankIdx(NumOperands);
 
   switch (Opc) {
   case TargetOpcode::G_FPEXT:
+  case TargetOpcode::G_FPTRUNC:
   case TargetOpcode::G_FCONSTANT:
     // Instruction having only floating-point operands (all scalars in VECRReg)
     getInstrPartialMappingIdxs(MI, MRI, /* isFP */ true, OpRegBankIdx);
     break;
   case TargetOpcode::G_SITOFP: {
     // Some of the floating-point instructions have mixed GPR and FP operands:
     // fine-tune the computed mapping.
     auto &Op0 = MI.getOperand(0);

test/CodeGen/X86/GlobalISel/legalize-fptrunc-scalar.mir

+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=x86_64-linux-gnu -run-pass=legalizer %s -o - | FileCheck %s --check-prefix=ALL
+--- |
+
+  define float @test_fptrunc(double %in) {
+    %res = fptrunc double %in to float
+    ret float %res
+  }
+
+...
+---
+name:            test_fptrunc
+alignment:       4
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: _ }
+  - { id: 1, class: _ }
+  - { id: 2, class: _ }
+  - { id: 3, class: _ }
+body:             |
+  bb.1 (%ir-block.0):
+    liveins: $xmm0
+
+    ; ALL-LABEL: name: test_fptrunc
+    ; ALL: liveins: $xmm0
+    ; ALL: [[COPY:%[0-9]+]]:_(s128) = COPY $xmm0
+    ; ALL: [[TRUNC:%[0-9]+]]:_(s64) = G_TRUNC [[COPY]](s128)
+    ; ALL: [[FPTRUNC:%[0-9]+]]:_(s32) = G_FPTRUNC [[TRUNC]](s64)
+    ; ALL: [[ANYEXT:%[0-9]+]]:_(s128) = G_ANYEXT [[FPTRUNC]](s32)
+    ; ALL: $xmm0 = COPY [[ANYEXT]](s128)
+    ; ALL: RET 0, implicit $xmm0
+    %1:_(s128) = COPY $xmm0
+    %0:_(s64) = G_TRUNC %1(s128)
+    %2:_(s32) = G_FPTRUNC %0(s64)
+    %3:_(s128) = G_ANYEXT %2(s32)
+    $xmm0 = COPY %3(s128)
+    RET 0, implicit $xmm0
+
+...

test/CodeGen/X86/GlobalISel/regbankselect-X86_64.mir

--- |
   }
 
   define double @test_fpext(float %a) {
   entry:
     %conv = fpext float %a to double
     ret double %conv
   }
 
+  define float @test_fptrunc(double %a) {
+  entry:
+    %conv = fptrunc double %a to float
+    ret float %conv
+  }
+
   define void @test_fconstant() {
     ret void
   }
 
   define float @int32_to_float(i32 %a) {
   entry:
     %conv = sitofp i32 %a to float
     ret float %conv
bb.1.entry:
     %0:_(s32) = G_TRUNC %1(s128)
     %2:_(s64) = G_FPEXT %0(s32)
     %3:_(s128) = G_ANYEXT %2(s64)
     $xmm0 = COPY %3(s128)
     RET 0, implicit $xmm0
 
 ...
 ---
+name:            test_fptrunc
+alignment:       4
+legalized:       true
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: _ }
+  - { id: 1, class: _ }
+  - { id: 2, class: _ }
+  - { id: 3, class: _ }
+body:             |
+  bb.1.entry:
+    liveins: $xmm0
+
+    ; FAST-LABEL: name: test_fptrunc
+    ; FAST: liveins: $xmm0
+    ; FAST: [[COPY:%[0-9]+]]:vecr(s128) = COPY $xmm0
+    ; FAST: [[TRUNC:%[0-9]+]]:vecr(s64) = G_TRUNC [[COPY]](s128)
+    ; FAST: [[FPTRUNC:%[0-9]+]]:vecr(s32) = G_FPTRUNC [[TRUNC]](s64)
+    ; FAST: [[ANYEXT:%[0-9]+]]:vecr(s128) = G_ANYEXT [[FPTRUNC]](s32)
+    ; FAST: $xmm0 = COPY [[ANYEXT]](s128)
+    ; FAST: RET 0, implicit $xmm0
+    ; GREEDY-LABEL: name: test_fptrunc
+    ; GREEDY: liveins: $xmm0
+    ; GREEDY: [[COPY:%[0-9]+]]:vecr(s128) = COPY $xmm0
+    ; GREEDY: [[TRUNC:%[0-9]+]]:vecr(s64) = G_TRUNC [[COPY]](s128)
+    ; GREEDY: [[FPTRUNC:%[0-9]+]]:vecr(s32) = G_FPTRUNC [[TRUNC]](s64)
+    ; GREEDY: [[ANYEXT:%[0-9]+]]:vecr(s128) = G_ANYEXT [[FPTRUNC]](s32)
+    ; GREEDY: $xmm0 = COPY [[ANYEXT]](s128)
+    ; GREEDY: RET 0, implicit $xmm0
+    %1:_(s128) = COPY $xmm0
+    %0:_(s64) = G_TRUNC %1(s128)
+    %2:_(s32) = G_FPTRUNC %0(s64)
+    %3:_(s128) = G_ANYEXT %2(s32)
+    $xmm0 = COPY %3(s128)
+    RET 0, implicit $xmm0
+
+...
+---
 name:            test_fconstant
 # ALL-LABEL: name:            test_fconstant
 legalized:       true
 registers:
   - { id: 0, class: _ }
   - { id: 1, class: _ }
 body: |
   bb.0:

test/CodeGen/X86/GlobalISel/select-fptrunc-scalar.mir

+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=x86_64-linux-gnu -run-pass=instruction-select -verify-machineinstrs %s -o - | FileCheck %s --check-prefix=ALL
+--- |
+
+  define float @test_fptrunc(double %in) {
+    %res = fptrunc double %in to float
+    ret float %res
+  }
+
+...
+---
+name:            test_fptrunc
+alignment:       4
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: vecr }
+  - { id: 1, class: vecr }
+  - { id: 2, class: vecr }
+  - { id: 3, class: vecr }
+body:             |
+  bb.1 (%ir-block.0):
+    liveins: $xmm0
+
+    ; ALL-LABEL: name: test_fptrunc
+    ; ALL: liveins: $xmm0
+    ; ALL: [[COPY:%[0-9]+]]:vr128 = COPY $xmm0
+    ; ALL: [[COPY1:%[0-9]+]]:fr64 = COPY [[COPY]]
+    ; ALL: [[CVTSD2SSrr:%[0-9]+]]:fr32 = CVTSD2SSrr [[COPY1]]
+    ; ALL: [[COPY2:%[0-9]+]]:vr128 = COPY [[CVTSD2SSrr]]
+    ; ALL: $xmm0 = COPY [[COPY2]]
+    ; ALL: RET 0, implicit $xmm0
+    %1:vecr(s128) = COPY $xmm0
+    %0:vecr(s64) = G_TRUNC %1(s128)
+    %2:vecr(s32) = G_FPTRUNC %0(s64)
+    %3:vecr(s128) = G_ANYEXT %2(s32)
+    $xmm0 = COPY %3(s128)
+    RET 0, implicit $xmm0
+
+...

test/CodeGen/X86/GlobalISel/x86_64-irtranslator.ll

define i64 @test_sdiv_i64(i64 %arg1, i64 %arg2) {
   ; CHECK:   [[COPY:%[0-9]+]]:_(s64) = COPY $rdi
   ; CHECK:   [[COPY1:%[0-9]+]]:_(s64) = COPY $rsi
   ; CHECK:   [[SDIV:%[0-9]+]]:_(s64) = G_SDIV [[COPY]], [[COPY1]]
   ; CHECK:   $rax = COPY [[SDIV]](s64)
   ; CHECK:   RET 0, implicit $rax
   %res = sdiv i64 %arg1, %arg2
   ret i64 %res
 }
+define float @test_fptrunc(double %in) {
+  ; CHECK-LABEL: name: test_fptrunc
+  ; CHECK: bb.1 (%ir-block.0):
+  ; CHECK:   liveins: $xmm0
+  ; CHECK:   [[COPY:%[0-9]+]]:_(s128) = COPY $xmm0
+  ; CHECK:   [[TRUNC:%[0-9]+]]:_(s64) = G_TRUNC [[COPY]](s128)
+  ; CHECK:   [[FPTRUNC:%[0-9]+]]:_(s32) = G_FPTRUNC [[TRUNC]](s64)
+  ; CHECK:   [[ANYEXT:%[0-9]+]]:_(s128) = G_ANYEXT [[FPTRUNC]](s32)
+  ; CHECK:   $xmm0 = COPY [[ANYEXT]](s128)
+  ; CHECK:   RET 0, implicit $xmm0
+  %res = fptrunc double %in to float
+  ret float %res
+}