[GlobalIsel][X86]] Legalize G_CONSTANT_FOLD_BARRIER

[RKSimon]

LGTM

llvm/lib/Target/X86/X86LegalizerInfo.cpp

X86LegalizerInfo::X86LegalizerInfo(const X86Subtarget &STI,
   getActionDefinitionsBuilder({G_MEMCPY, G_MEMMOVE, G_MEMSET}).libcall();
 
   // fp intrinsics
   getActionDefinitionsBuilder(G_INTRINSIC_ROUNDEVEN)
       .scalarize(0)
       .minScalar(0, LLT::scalar(32))
       .libcall();
 
-  getActionDefinitionsBuilder(G_FREEZE)
+  getActionDefinitionsBuilder({G_FREEZE, G_CONSTANT_FOLD_BARRIER})
     .legalFor({s8, s16, s32, s64, p0})
     .widenScalarToNextPow2(0, /*Min=*/8)
     .clampScalar(0, s8, sMaxScalar);
 
   getLegacyLegalizerInfo().computeTables();
   verify(*STI.getInstrInfo());
 }
 
 bool X86LegalizerInfo::legalizeIntrinsic(LegalizerHelper &Helper,
                                          MachineInstr &MI) const {
   return true;
 }

llvm/test/CodeGen/X86/GlobalISel/legalize-constant-fold.mir

+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 2
+# RUN: llc -mtriple=i386-linux-gnu -run-pass=legalizer %s -o - | FileCheck %s --check-prefix=X86-32
+
+# test constant fold barrier
+
+...
+---
+name:            test_fold64
+body:             |
+  bb.0:
+    ; X86-32-LABEL: name: test_fold64
+    ; X86-32: [[DEF:%[0-9]+]]:_(s64) = IMPLICIT_DEF
+    ; X86-32-NEXT: [[CONSTANT_FOLD_BARRIER:%[0-9]+]]:_(s64) = G_CONSTANT_FOLD_BARRIER [[DEF]]
+    ; X86-32-NEXT: [[COPY:%[0-9]+]]:_(s64) = COPY [[CONSTANT_FOLD_BARRIER]](s64)
+    ; X86-32-NEXT: RET 0, implicit [[COPY]](s64)
+    %0:_(s64) = IMPLICIT_DEF
+    %1:_(s64) = G_CONSTANT_FOLD_BARRIER %0
+    %2:_(s64) = COPY %1(s64)
+    RET 0, implicit %2
+
+...
+---
+name:            test_fold32
+body:             |
+  bb.0:
+    ; X86-32-LABEL: name: test_fold32
+    ; X86-32: [[DEF:%[0-9]+]]:_(s32) = IMPLICIT_DEF
+    ; X86-32-NEXT: [[CONSTANT_FOLD_BARRIER:%[0-9]+]]:_(s32) = G_CONSTANT_FOLD_BARRIER [[DEF]]
+    ; X86-32-NEXT: [[COPY:%[0-9]+]]:_(s32) = COPY [[CONSTANT_FOLD_BARRIER]](s32)
+    ; X86-32-NEXT: RET 0, implicit [[COPY]](s32)
+    %0:_(s32) = IMPLICIT_DEF
+    %1:_(s32) = G_CONSTANT_FOLD_BARRIER %0
+    %2:_(s32) = COPY %1(s32)
+    RET 0, implicit %2
+
+...
+---
+name:            test_fold16
+body:             |
+  bb.0:
+    ; X86-32-LABEL: name: test_fold16
+    ; X86-32: [[DEF:%[0-9]+]]:_(s16) = IMPLICIT_DEF
+    ; X86-32-NEXT: [[CONSTANT_FOLD_BARRIER:%[0-9]+]]:_(s16) = G_CONSTANT_FOLD_BARRIER [[DEF]]
+    ; X86-32-NEXT: [[COPY:%[0-9]+]]:_(s16) = COPY [[CONSTANT_FOLD_BARRIER]](s16)
+    ; X86-32-NEXT: RET 0, implicit [[COPY]](s16)
+    %0:_(s16) = IMPLICIT_DEF
+    %1:_(s16) = G_CONSTANT_FOLD_BARRIER %0
+    %2:_(s16) = COPY %1(s16)
+    RET 0, implicit %2
+
+...
+---
+name:            test_fold8
+body:             |
+  bb.0:
+    ; X86-32-LABEL: name: test_fold8
+    ; X86-32: [[DEF:%[0-9]+]]:_(s8) = IMPLICIT_DEF
+    ; X86-32-NEXT: [[CONSTANT_FOLD_BARRIER:%[0-9]+]]:_(s8) = G_CONSTANT_FOLD_BARRIER [[DEF]]
+    ; X86-32-NEXT: [[COPY:%[0-9]+]]:_(s8) = COPY [[CONSTANT_FOLD_BARRIER]](s8)
+    ; X86-32-NEXT: RET 0, implicit [[COPY]](s8)
+    %0:_(s8) = IMPLICIT_DEF
+    %1:_(s8) = G_CONSTANT_FOLD_BARRIER %0
+    %2:_(s8) = COPY %1(s8)
+    RET 0, implicit %2
+
+...