diff --git a/llvm/test/CodeGen/AMDGPU/GlobalISel/knownbits-ptrtoaddr.mir b/llvm/test/CodeGen/AMDGPU/GlobalISel/knownbits-ptrtoaddr.mir
new file mode 100644
index 0000000000000..3fcd24ca0d031
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/GlobalISel/knownbits-ptrtoaddr.mir
@@ -0,0 +1,108 @@
+# NOTE: Assertions have been autogenerated by utils/update_givaluetracking_test_checks.py UTC_ARGS: --version 5
+# RUN: llc -mtriple=amdgcn -passes="print<gisel-value-tracking>" %s -filetype=null 2>&1 | FileCheck %s
+## Check that we don't incorrectly assume known zeroes for and extend of a truncated ptrtoaddr
+---
+## We should see 48 unknown bits.
+name:            PtrToAddr
+body:             |
+  bb.0:
+  ; CHECK-LABEL: name: @PtrToAddr
+  ; CHECK-NEXT: %0:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %1:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %2:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %3:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %4:_ KnownBits:???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %5:_ KnownBits:???????????????????????????????????????????????? SignBits:1
+    %0:_(s32) = COPY $vgpr0
+    %1:_(s32) = COPY $vgpr1
+    %2:_(s32) = COPY $vgpr2
+    %3:_(s32) = COPY $vgpr3
+    %4:_(p8) = G_MERGE_VALUES %0(s32), %1(s32), %2(s32), %3(s32)
+    %5:_(s48) = G_PTRTOADDR %4(p8)
+...
+---
+## We should see 208 high zeroes followed by 48 unknown bits for extending PtrToAddr.
+## FIXME: this is currently wrong
+name:            PtrToAddrExt
+body:             |
+  bb.0:
+  ; CHECK-LABEL: name: @PtrToAddrExt
+  ; CHECK-NEXT: %0:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %1:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %2:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %3:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %4:_ KnownBits:???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %5:_ KnownBits:00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? SignBits:128
+    %0:_(s32) = COPY $vgpr0
+    %1:_(s32) = COPY $vgpr1
+    %2:_(s32) = COPY $vgpr2
+    %3:_(s32) = COPY $vgpr3
+    %4:_(p8) = G_MERGE_VALUES %0(s32), %1(s32), %2(s32), %3(s32)
+    %5:_(s256) = G_PTRTOADDR %4(p8)
+...
+---
+## We should see 32 unknown bits for truncating PtrToAddr.
+name:            PtrToAddrTrunc
+body:             |
+  bb.0:
+  ; CHECK-LABEL: name: @PtrToAddrTrunc
+  ; CHECK-NEXT: %0:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %1:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %2:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %3:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %4:_ KnownBits:???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %5:_ KnownBits:???????????????????????????????? SignBits:1
+    %0:_(s32) = COPY $vgpr0
+    %1:_(s32) = COPY $vgpr1
+    %2:_(s32) = COPY $vgpr2
+    %3:_(s32) = COPY $vgpr3
+    %4:_(p8) = G_MERGE_VALUES %0(s32), %1(s32), %2(s32), %3(s32)
+    %5:_(s32) = G_PTRTOADDR %4(p8)
+...
+---
+## Cbeck that truncating and then extending the G_PTRTOADDR result fills
+## all bits above the index bitwidth with known zeroes.
+## We should see all zero high bits with 32 unknown bits.
+name:            PtrToAddrTruncExplicitExt
+body:             |
+  bb.0:
+  ; CHECK-LABEL: name: @PtrToAddrTruncExplicitExt
+  ; CHECK-NEXT: %0:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %1:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %2:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %3:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %4:_ KnownBits:???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %5:_ KnownBits:???????????????????????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %6:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %7:_ KnownBits:000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000???????????????????????????????? SignBits:96
+    %0:_(s32) = COPY $vgpr0
+    %1:_(s32) = COPY $vgpr1
+    %2:_(s32) = COPY $vgpr2
+    %3:_(s32) = COPY $vgpr3
+    %4:_(p8) = G_MERGE_VALUES %0(s32), %1(s32), %2(s32), %3(s32)
+    %5:_(s48) = G_PTRTOADDR %4(p8)
+    %6:_(s32) = G_TRUNC %5(s48)
+    %7:_(s128) = G_ZEXT %6(s32)
+...
+---
+## Same test again but this time have the G_PTRTOADDR do the truncation.
+## We should see all zero high bits with 48 unknown bits.
+name:            PtrToAddrTruncImplicitExt
+body:             |
+  bb.0:
+  ; CHECK-LABEL: name: @PtrToAddrTruncImplicitExt
+  ; CHECK-NEXT: %0:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %1:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %2:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %3:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %4:_ KnownBits:???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %5:_ KnownBits:???????????????????????????????? SignBits:1
+  ; CHECK-NEXT: %6:_ KnownBits:000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000???????????????????????????????? SignBits:96
+    %0:_(s32) = COPY $vgpr0
+    %1:_(s32) = COPY $vgpr1
+    %2:_(s32) = COPY $vgpr2
+    %3:_(s32) = COPY $vgpr3
+    %4:_(p8) = G_MERGE_VALUES %0(s32), %1(s32), %2(s32), %3(s32)
+    %5:_(s32) = G_PTRTOADDR %4(p8)
+    %6:_(s128) = G_ZEXT %5(s32)
+...