[PATCH] D99298: [AArch64][GlobalISel] Make G_UBFX/G_SBFX legalization check for constants

[Jessica Paquette via Phabricator via llvm-commits]

paquette created this revision.
paquette added a reviewer: aemerson.
Herald added subscribers: danielkiss, hiraditya, kristof.beyls, rovka.
paquette requested review of this revision.
Herald added a project: LLVM.

The original rule just checked the type, but this is actually only legal if it has a constant.

Since the legalizer isn't supposed to be conditional, we have to check this.

(I'll probably have to make the bitfield extract combines I've been putting up AArch64-specific for now and come up with a way to check for custom legalization rules in the combiner.)


https://reviews.llvm.org/D99298

Files:
  llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
  llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.h
  llvm/test/CodeGen/AArch64/GlobalISel/legalizer-info-validation.mir


Index: llvm/test/CodeGen/AArch64/GlobalISel/legalizer-info-validation.mir
===================================================================
--- llvm/test/CodeGen/AArch64/GlobalISel/legalizer-info-validation.mir
+++ llvm/test/CodeGen/AArch64/GlobalISel/legalizer-info-validation.mir
@@ -675,12 +675,12 @@
 # DEBUG-NEXT: .. type index coverage check SKIPPED: no rules defined
 # DEBUG-NEXT: .. imm index coverage check SKIPPED: no rules defined
 # DEBUG-NEXT: G_SBFX (opcode {{[0-9]+}}): 1 type index, 0 imm indices
-# DEBUG-NEXT: .. the first uncovered type index: 1, OK
-# DEBUG-NEXT: .. the first uncovered imm index: 0, OK
+# DEBUG-NEXT: .. type index coverage check SKIPPED: user-defined predicate detected
+# DEBUG-NEXT: .. imm index coverage check SKIPPED: user-defined predicate detected
 # DEBUG-NEXT: G_UBFX (opcode {{[0-9]+}}): 1 type index, 0 imm indices
 # DEBUG-NEXT: .. opcode {{[0-9]+}} is aliased to {{[0-9]+}}
-# DEBUG-NEXT: .. the first uncovered type index: 1, OK
-# DEBUG-NEXT: .. the first uncovered imm index: 0, OK
+# DEBUG-NEXT: .. type index coverage check SKIPPED: user-defined predicate detected
+# DEBUG-NEXT: .. imm index coverage check SKIPPED: user-defined predicate detected
 # CHECK-NOT: ill-defined
 
 ---
Index: llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.h
===================================================================
--- llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.h
+++ llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.h
@@ -47,6 +47,8 @@
                                   MachineIRBuilder &MIRBuilder,
                                   GISelChangeObserver &Observer) const;
   bool legalizeVectorTrunc(MachineInstr &MI, LegalizerHelper &Helper) const;
+  bool legalizeBitfieldExtract(MachineInstr &MI, MachineRegisterInfo &MRI,
+                               LegalizerHelper &Helper) const;
   const AArch64Subtarget *ST;
 };
 } // End llvm namespace.
Index: llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
===================================================================
--- llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
+++ llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
@@ -702,7 +702,8 @@
 
   getActionDefinitionsBuilder({G_FSHL, G_FSHR}).lower();
 
-  getActionDefinitionsBuilder({G_SBFX, G_UBFX}).legalFor({s32, s64});
+  getActionDefinitionsBuilder({G_SBFX, G_UBFX}).customFor({s32, s64});
+
   computeTables();
   verify(*ST.getInstrInfo());
 }
@@ -729,6 +730,9 @@
     return legalizeSmallCMGlobalValue(MI, MRI, MIRBuilder, Observer);
   case TargetOpcode::G_TRUNC:
     return legalizeVectorTrunc(MI, Helper);
+  case TargetOpcode::G_SBFX:
+  case TargetOpcode::G_UBFX:
+    return legalizeBitfieldExtract(MI, MRI, Helper);
   }
 
   llvm_unreachable("expected switch to return");
@@ -948,3 +952,11 @@
   MI.eraseFromParent();
   return true;
 }
+
+bool AArch64LegalizerInfo::legalizeBitfieldExtract(
+    MachineInstr &MI, MachineRegisterInfo &MRI, LegalizerHelper &Helper) const {
+  // Only legal if we can select immediate forms.
+  // TODO: Lower this otherwise.
+  return getConstantVRegValWithLookThrough(MI.getOperand(2).getReg(), MRI) &&
+         getConstantVRegValWithLookThrough(MI.getOperand(3).getReg(), MRI);
+}


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