[InferAddrSpaces] Correctly replace identical operands of insts (#82610)

It's important for PHI nodes because if a PHI node has multiple edges
coming from the same block, we can have the same incoming value multiple
times in the list of incoming values. All of those need to be consistent
(exact same Value*) otherwise verifier complains.

Fixes SWDEV-445797

2 files changed, 77 insertions, 5 deletions

diff --git a/llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp b/llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp
index 1bf50d7..851eab0 100644
--- a/llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp
+++ b/llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp
@@ -1221,6 +1221,7 @@ bool InferAddressSpacesImpl::rewriteWithNewAddressSpaces(
     Value::use_iterator I, E, Next;
     for (I = V->use_begin(), E = V->use_end(); I != E;) {
       Use &U = *I;
+      User *CurUser = U.getUser();
 
       // Some users may see the same pointer operand in multiple operands. Skip
       // to the next instruction.
@@ -1231,11 +1232,10 @@ bool InferAddressSpacesImpl::rewriteWithNewAddressSpaces(
         // If V is used as the pointer operand of a compatible memory operation,
         // sets the pointer operand to NewV. This replacement does not change
         // the element type, so the resultant load/store is still valid.
-        U.set(NewV);
+        CurUser->replaceUsesOfWith(V, NewV);
         continue;
       }
 
-      User *CurUser = U.getUser();
       // Skip if the current user is the new value itself.
       if (CurUser == NewV)
         continue;
@@ -1311,10 +1311,13 @@ bool InferAddressSpacesImpl::rewriteWithNewAddressSpaces(
 
           while (isa<PHINode>(InsertPos))
             ++InsertPos;
-          U.set(new AddrSpaceCastInst(NewV, V->getType(), "", &*InsertPos));
+          // This instruction may contain multiple uses of V, update them all.
+          CurUser->replaceUsesOfWith(
+              V, new AddrSpaceCastInst(NewV, V->getType(), "", &*InsertPos));
         } else {
-          U.set(ConstantExpr::getAddrSpaceCast(cast<Constant>(NewV),
-                                               V->getType()));
+          CurUser->replaceUsesOfWith(
+              V, ConstantExpr::getAddrSpaceCast(cast<Constant>(NewV),
+                                                V->getType()));
         }
       }
     }
diff --git a/llvm/test/Transforms/InferAddressSpaces/AMDGPU/multiple-uses-of-val.ll b/llvm/test/Transforms/InferAddressSpaces/AMDGPU/multiple-uses-of-val.ll
new file mode 100644
index 0000000..717bd09
--- /dev/null
+++ b/llvm/test/Transforms/InferAddressSpaces/AMDGPU/multiple-uses-of-val.ll
@@ -0,0 +1,69 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -mtriple=amdgcn-amd-amdhsa -mcpu=gfx90a -S -passes=infer-address-spaces --verify-each %s | FileCheck %s
+
+; Inst can use a value multiple time. When we're inserting an addrspacecast to flat,
+; it's important all the identical uses use an indentical replacement, especially
+; for PHIs.
+
+define amdgpu_kernel void @test_phi() {
+; CHECK-LABEL: @test_phi(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[LOADED_PTR:%.*]] = load ptr, ptr addrspace(4) null, align 8
+; CHECK-NEXT:    [[TMP0:%.*]] = addrspacecast ptr [[LOADED_PTR]] to ptr addrspace(1)
+; CHECK-NEXT:    br label [[BB0:%.*]]
+; CHECK:       bb0:
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr i64, ptr addrspace(1) [[TMP0]], i64 3
+; CHECK-NEXT:    [[TMP1:%.*]] = addrspacecast ptr addrspace(1) [[GEP]] to ptr
+; CHECK-NEXT:    switch i32 0, label [[END:%.*]] [
+; CHECK-NEXT:      i32 1, label [[END]]
+; CHECK-NEXT:      i32 4, label [[END]]
+; CHECK-NEXT:      i32 5, label [[BB1:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[TMP2:%.*]] = load double, ptr addrspace(1) [[GEP]], align 16
+; CHECK-NEXT:    br label [[END]]
+; CHECK:       end:
+; CHECK-NEXT:    [[RETVAL_SROA_0_0_I569_PH:%.*]] = phi ptr [ null, [[BB1]] ], [ [[TMP1]], [[BB0]] ], [ [[TMP1]], [[BB0]] ], [ [[TMP1]], [[BB0]] ]
+; CHECK-NEXT:    ret void
+;
+entry:
+  %loaded.ptr = load ptr, ptr addrspace(4) null, align 8
+  br label %bb0
+
+bb0:
+  %gep = getelementptr i64, ptr %loaded.ptr, i64 3
+  switch i32 0, label %end [
+  i32 1, label %end
+  i32 4, label %end
+  i32 5, label %bb1
+  ]
+
+bb1:
+  %0 = load double, ptr %gep, align 16
+  br label %end
+
+end:
+  %retval.sroa.0.0.i569.ph = phi ptr [ null, %bb1 ], [ %gep, %bb0 ], [ %gep, %bb0 ], [ %gep, %bb0 ]
+  ret void
+}
+
+declare void @uses_ptrs(ptr, ptr, ptr)
+
+; We shouldn't treat PHIs differently, even other users should have the same treatment.
+; All occurences of %gep are replaced with an identical value.
+define amdgpu_kernel void @test_other() {
+; CHECK-LABEL: @test_other(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[LOADED_PTR:%.*]] = load ptr, ptr addrspace(4) null, align 8
+; CHECK-NEXT:    [[TMP0:%.*]] = addrspacecast ptr [[LOADED_PTR]] to ptr addrspace(1)
+; CHECK-NEXT:    [[TMP1:%.*]] = addrspacecast ptr addrspace(1) [[TMP0]] to ptr
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr i64, ptr [[TMP1]], i64 3
+; CHECK-NEXT:    call void @uses_ptrs(ptr [[GEP]], ptr [[GEP]], ptr [[GEP]])
+; CHECK-NEXT:    ret void
+;
+entry:
+  %loaded.ptr = load ptr, ptr addrspace(4) null, align 8
+  %gep = getelementptr i64, ptr %loaded.ptr, i64 3
+  call void @uses_ptrs(ptr %gep, ptr %gep, ptr %gep)
+  ret void
+}