Index: llvm/include/llvm/CodeGen/GlobalISel/LegalizerInfo.h
===================================================================
--- llvm/include/llvm/CodeGen/GlobalISel/LegalizerInfo.h
+++ llvm/include/llvm/CodeGen/GlobalISel/LegalizerInfo.h
@@ -252,6 +252,9 @@
 /// is not a power of 2.
 LegalityPredicate scalarOrEltSizeNotPow2(unsigned TypeIdx);
 
+/// True if the total bitwidth of the specified type index is \p Size bits.
+LegalityPredicate sizeIs(unsigned TypeIdx, unsigned Size);
+
 /// True iff the specified type indices are both the same bit size.
 LegalityPredicate sameSize(unsigned TypeIdx0, unsigned TypeIdx1);
 /// True iff the specified MMO index has a size that is not a power of 2
Index: llvm/lib/CodeGen/GlobalISel/LegalityPredicates.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/LegalityPredicates.cpp
+++ llvm/lib/CodeGen/GlobalISel/LegalityPredicates.cpp
@@ -126,6 +126,12 @@
   };
 }
 
+LegalityPredicate LegalityPredicates::sizeIs(unsigned TypeIdx, unsigned Size) {
+  return [=](const LegalityQuery &Query) {
+    return Query.Types[TypeIdx].getSizeInBits() == Size;
+  };
+}
+
 LegalityPredicate LegalityPredicates::sameSize(unsigned TypeIdx0,
                                                unsigned TypeIdx1) {
   return [=](const LegalityQuery &Query) {
Index: llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -1210,6 +1210,14 @@
     MI.eraseFromParent();
     return Legalized;
   }
+  case TargetOpcode::G_PTRMASK: {
+    if (TypeIdx != 1)
+      return UnableToLegalize;
+    Observer.changingInstr(MI);
+    narrowScalarSrc(MI, NarrowTy, 2);
+    Observer.changedInstr(MI);
+    return Legalized;
+  }
   }
 }
 
@@ -2143,6 +2151,14 @@
     widenScalarDst(MI, WideTy, 0, TargetOpcode::G_TRUNC);
     Observer.changedInstr(MI);
     return Legalized;
+  case TargetOpcode::G_PTRMASK: {
+    if (TypeIdx != 1)
+      return UnableToLegalize;
+    Observer.changingInstr(MI);
+    widenScalarSrc(MI, WideTy, 2, TargetOpcode::G_ZEXT);
+    Observer.changedInstr(MI);
+    return Legalized;
+  }
   }
 }
 
Index: llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
+++ llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
@@ -66,12 +66,6 @@
   };
 }
 
-static LegalityPredicate sizeIs(unsigned TypeIdx, unsigned Size) {
-  return [=](const LegalityQuery &Query) {
-    return Query.Types[TypeIdx].getSizeInBits() == Size;
-  };
-}
-
 static LegalityPredicate isSmallOddVector(unsigned TypeIdx) {
   return [=](const LegalityQuery &Query) {
     const LLT Ty = Query.Types[TypeIdx];
@@ -560,14 +554,17 @@
       .scalarize(0);
   }
 
+  // FIXME: Clamp offset operand.
   getActionDefinitionsBuilder(G_PTR_ADD)
-    .scalarize(0)
-    .alwaysLegal();
+    .legalIf(isPointer(0))
+    .scalarize(0);
 
-  // TODO: Clamp mask to pointer sizes
   getActionDefinitionsBuilder(G_PTRMASK)
-    .scalarize(0)
-    .alwaysLegal();
+    .legalIf(typeInSet(1, {S64, S32}))
+    .minScalar(1, S32)
+    .maxScalarIf(sizeIs(0, 32), 1, S32)
+    .maxScalarIf(sizeIs(0, 64), 1, S64)
+    .scalarize(0);
 
   auto &CmpBuilder =
     getActionDefinitionsBuilder(G_ICMP)
Index: llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-ptrmask.mir
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-ptrmask.mir
@@ -0,0 +1,221 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=amdgcn-mesa-mesa3d -mcpu=fiji -O0 -run-pass=legalizer %s -o - | FileCheck %s
+
+---
+name: ptrmask_p1_s16
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1, $vgpr2
+
+    ; CHECK-LABEL: name: ptrmask_p1_s16
+    ; CHECK: [[COPY:%[0-9]+]]:_(p1) = COPY $vgpr0_vgpr1
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY $vgpr2
+    ; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 65535
+    ; CHECK: [[COPY2:%[0-9]+]]:_(s32) = COPY [[COPY1]](s32)
+    ; CHECK: [[AND:%[0-9]+]]:_(s32) = G_AND [[COPY2]], [[C]]
+    ; CHECK: [[PTRMASK:%[0-9]+]]:_(p1) = G_PTRMASK [[COPY]], [[AND]](s32)
+    ; CHECK: $vgpr0_vgpr1 = COPY [[PTRMASK]](p1)
+    %0:_(p1) = COPY $vgpr0_vgpr1
+    %1:_(s32) = COPY $vgpr2
+    %2:_(s16) = G_TRUNC %1
+    %3:_(p1) = G_PTRMASK %0, %2
+    $vgpr0_vgpr1 = COPY %3
+...
+
+---
+name: ptrmask_p1_s32
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1, $vgpr2
+
+    ; CHECK-LABEL: name: ptrmask_p1_s32
+    ; CHECK: [[COPY:%[0-9]+]]:_(p1) = COPY $vgpr0_vgpr1
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY $vgpr2
+    ; CHECK: [[PTRMASK:%[0-9]+]]:_(p1) = G_PTRMASK [[COPY]], [[COPY1]](s32)
+    ; CHECK: $vgpr0_vgpr1 = COPY [[PTRMASK]](p1)
+    %0:_(p1) = COPY $vgpr0_vgpr1
+    %1:_(s32) = COPY $vgpr2
+    %2:_(p1) = G_PTRMASK %0, %1
+    $vgpr0_vgpr1 = COPY %2
+...
+
+---
+name: ptrmask_p1_s64
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1, $vgpr2_vgpr3
+
+    ; CHECK-LABEL: name: ptrmask_p1_s64
+    ; CHECK: [[COPY:%[0-9]+]]:_(p1) = COPY $vgpr0_vgpr1
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s64) = COPY $vgpr2_vgpr3
+    ; CHECK: [[PTRMASK:%[0-9]+]]:_(p1) = G_PTRMASK [[COPY]], [[COPY1]](s64)
+    ; CHECK: $vgpr0_vgpr1 = COPY [[PTRMASK]](p1)
+    %0:_(p1) = COPY $vgpr0_vgpr1
+    %1:_(s64) = COPY $vgpr2_vgpr3
+    %2:_(p1) = G_PTRMASK %0, %1
+    $vgpr0_vgpr1 = COPY %2
+...
+
+---
+name: ptrmask_p1_s96
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1, $vgpr2_vgpr3_vgpr4
+
+    ; CHECK-LABEL: name: ptrmask_p1_s96
+    ; CHECK: [[COPY:%[0-9]+]]:_(p1) = COPY $vgpr0_vgpr1
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s96) = COPY $vgpr2_vgpr3_vgpr4
+    ; CHECK: [[TRUNC:%[0-9]+]]:_(s64) = G_TRUNC [[COPY1]](s96)
+    ; CHECK: [[PTRMASK:%[0-9]+]]:_(p1) = G_PTRMASK [[COPY]], [[TRUNC]](s64)
+    ; CHECK: $vgpr0_vgpr1 = COPY [[PTRMASK]](p1)
+    %0:_(p1) = COPY $vgpr0_vgpr1
+    %1:_(s96) = COPY $vgpr2_vgpr3_vgpr4
+    %2:_(p1) = G_PTRMASK %0, %1
+    $vgpr0_vgpr1 = COPY %2
+...
+
+---
+name: ptrmask_p0_s16
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1, $vgpr2
+
+    ; CHECK-LABEL: name: ptrmask_p0_s16
+    ; CHECK: [[COPY:%[0-9]+]]:_(p0) = COPY $vgpr0_vgpr1
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY $vgpr2
+    ; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 65535
+    ; CHECK: [[COPY2:%[0-9]+]]:_(s32) = COPY [[COPY1]](s32)
+    ; CHECK: [[AND:%[0-9]+]]:_(s32) = G_AND [[COPY2]], [[C]]
+    ; CHECK: [[PTRMASK:%[0-9]+]]:_(p0) = G_PTRMASK [[COPY]], [[AND]](s32)
+    ; CHECK: $vgpr0_vgpr1 = COPY [[PTRMASK]](p0)
+    %0:_(p0) = COPY $vgpr0_vgpr1
+    %1:_(s32) = COPY $vgpr2
+    %2:_(s16) = G_TRUNC %1
+    %3:_(p0) = G_PTRMASK %0, %2
+    $vgpr0_vgpr1 = COPY %3
+...
+
+---
+name: ptrmask_p0_s32
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1, $vgpr2
+
+    ; CHECK-LABEL: name: ptrmask_p0_s32
+    ; CHECK: [[COPY:%[0-9]+]]:_(p0) = COPY $vgpr0_vgpr1
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY $vgpr2
+    ; CHECK: [[PTRMASK:%[0-9]+]]:_(p0) = G_PTRMASK [[COPY]], [[COPY1]](s32)
+    ; CHECK: $vgpr0_vgpr1 = COPY [[PTRMASK]](p0)
+    %0:_(p0) = COPY $vgpr0_vgpr1
+    %1:_(s32) = COPY $vgpr2
+    %2:_(p0) = G_PTRMASK %0, %1
+    $vgpr0_vgpr1 = COPY %2
+...
+
+---
+name: ptrmask_p0_s64
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1, $vgpr2_vgpr3
+
+    ; CHECK-LABEL: name: ptrmask_p0_s64
+    ; CHECK: [[COPY:%[0-9]+]]:_(p0) = COPY $vgpr0_vgpr1
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s64) = COPY $vgpr2_vgpr3
+    ; CHECK: [[PTRMASK:%[0-9]+]]:_(p0) = G_PTRMASK [[COPY]], [[COPY1]](s64)
+    ; CHECK: $vgpr0_vgpr1 = COPY [[PTRMASK]](p0)
+    %0:_(p0) = COPY $vgpr0_vgpr1
+    %1:_(s64) = COPY $vgpr2_vgpr3
+    %2:_(p0) = G_PTRMASK %0, %1
+    $vgpr0_vgpr1 = COPY %2
+...
+
+---
+name: ptrmask_p0_s96
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1, $vgpr2_vgpr3_vgpr4
+
+    ; CHECK-LABEL: name: ptrmask_p0_s96
+    ; CHECK: [[COPY:%[0-9]+]]:_(p0) = COPY $vgpr0_vgpr1
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s96) = COPY $vgpr2_vgpr3_vgpr4
+    ; CHECK: [[TRUNC:%[0-9]+]]:_(s64) = G_TRUNC [[COPY1]](s96)
+    ; CHECK: [[PTRMASK:%[0-9]+]]:_(p0) = G_PTRMASK [[COPY]], [[TRUNC]](s64)
+    ; CHECK: $vgpr0_vgpr1 = COPY [[PTRMASK]](p0)
+    %0:_(p0) = COPY $vgpr0_vgpr1
+    %1:_(s96) = COPY $vgpr2_vgpr3_vgpr4
+    %2:_(p0) = G_PTRMASK %0, %1
+    $vgpr0_vgpr1 = COPY %2
+...
+
+---
+name: ptrmask_p3_s16
+body: |
+  bb.0:
+    liveins: $vgpr0, $vgpr1
+
+    ; CHECK-LABEL: name: ptrmask_p3_s16
+    ; CHECK: [[COPY:%[0-9]+]]:_(p3) = COPY $vgpr0
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY $vgpr1
+    ; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 65535
+    ; CHECK: [[COPY2:%[0-9]+]]:_(s32) = COPY [[COPY1]](s32)
+    ; CHECK: [[AND:%[0-9]+]]:_(s32) = G_AND [[COPY2]], [[C]]
+    ; CHECK: [[PTRMASK:%[0-9]+]]:_(p3) = G_PTRMASK [[COPY]], [[AND]](s32)
+    ; CHECK: $vgpr0 = COPY [[PTRMASK]](p3)
+    %0:_(p3) = COPY $vgpr0
+    %1:_(s32) = COPY $vgpr1
+    %2:_(s16) = G_TRUNC %1
+    %3:_(p3) = G_PTRMASK %0, %2
+    $vgpr0 = COPY %3
+...
+
+---
+name: ptrmask_p3_s32
+body: |
+  bb.0:
+    liveins: $vgpr0, $vgpr1
+
+    ; CHECK-LABEL: name: ptrmask_p3_s32
+    ; CHECK: [[COPY:%[0-9]+]]:_(p3) = COPY $vgpr0
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY $vgpr1
+    ; CHECK: [[PTRMASK:%[0-9]+]]:_(p3) = G_PTRMASK [[COPY]], [[COPY1]](s32)
+    ; CHECK: $vgpr0 = COPY [[PTRMASK]](p3)
+    %0:_(p3) = COPY $vgpr0
+    %1:_(s32) = COPY $vgpr1
+    %2:_(p3) = G_PTRMASK %0, %1
+    $vgpr0 = COPY %2
+...
+
+---
+name: ptrmask_p3_s64
+body: |
+  bb.0:
+    liveins: $vgpr0, $vgpr1_vgpr2
+
+    ; CHECK-LABEL: name: ptrmask_p3_s64
+    ; CHECK: [[COPY:%[0-9]+]]:_(p3) = COPY $vgpr0
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s64) = COPY $vgpr1_vgpr2
+    ; CHECK: [[PTRMASK:%[0-9]+]]:_(p3) = G_PTRMASK [[COPY]], [[COPY1]](s64)
+    ; CHECK: $vgpr0 = COPY [[PTRMASK]](p3)
+    %0:_(p3) = COPY $vgpr0
+    %1:_(s64) = COPY $vgpr1_vgpr2
+    %2:_(p3) = G_PTRMASK %0, %1
+    $vgpr0 = COPY %2
+...
+
+---
+name: ptrmask_p3_s96
+body: |
+  bb.0:
+    liveins: $vgpr0, $vgpr1_vgpr2_vgpr3
+
+    ; CHECK-LABEL: name: ptrmask_p3_s96
+    ; CHECK: [[COPY:%[0-9]+]]:_(p3) = COPY $vgpr0
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s96) = COPY $vgpr1_vgpr2_vgpr3
+    ; CHECK: [[TRUNC:%[0-9]+]]:_(s32) = G_TRUNC [[COPY1]](s96)
+    ; CHECK: [[PTRMASK:%[0-9]+]]:_(p3) = G_PTRMASK [[COPY]], [[TRUNC]](s32)
+    ; CHECK: $vgpr0 = COPY [[PTRMASK]](p3)
+    %0:_(p3) = COPY $vgpr0
+    %1:_(s96) = COPY $vgpr1_vgpr2_vgpr3
+    %2:_(p3) = G_PTRMASK %0, %1
+    $vgpr0 = COPY %2
+...