[PATCH] D136524: [InstCombine] Handle select inst when eliminating constant memcpy

[Anshil Gandhi via Phabricator via llvm-commits]

gandhi21299 updated this revision to Diff 491402.
gandhi21299 added a comment.

- use isAvailable as requested by reviewer
- update test accordingly


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D136524/new/

https://reviews.llvm.org/D136524

Files:
  llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
  llvm/test/Transforms/InstCombine/ptr-replace-alloca.ll


Index: llvm/test/Transforms/InstCombine/ptr-replace-alloca.ll
===================================================================
--- llvm/test/Transforms/InstCombine/ptr-replace-alloca.ll
+++ llvm/test/Transforms/InstCombine/ptr-replace-alloca.ll
@@ -366,9 +366,7 @@
 define i8 @select_same_addrspace_remove_alloca(i1 %cond, ptr %p) {
 ; CHECK-LABEL: @select_same_addrspace_remove_alloca(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[ALLOCA:%.*]] = alloca [32 x i8], align 1
-; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr noundef nonnull align 1 dereferenceable(32) [[ALLOCA]], ptr noundef nonnull align 16 dereferenceable(32) @g1, i64 32, i1 false)
-; CHECK-NEXT:    [[PTR:%.*]] = select i1 [[COND:%.*]], ptr [[ALLOCA]], ptr [[P:%.*]]
+; CHECK-NEXT:    [[PTR:%.*]] = select i1 [[COND:%.*]], ptr @g1, ptr [[P:%.*]]
 ; CHECK-NEXT:    [[LOAD:%.*]] = load i8, ptr [[PTR]], align 1
 ; CHECK-NEXT:    ret i8 [[LOAD]]
 ;
@@ -417,13 +415,8 @@
 define i8 @select_diff_addrspace_remove_alloca(i1 %cond, ptr %p) {
 ; CHECK-LABEL: @select_diff_addrspace_remove_alloca(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[ALLOCA:%.*]] = alloca [32 x i8], align 1
-; CHECK-NEXT:    call void @llvm.memcpy.p0.p1.i64(ptr noundef nonnull align 1 dereferenceable(32) [[ALLOCA]], ptr addrspace(1) noundef align 16 dereferenceable(32) @g2, i64 32, i1 false)
-; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds [32 x i8], ptr [[ALLOCA]], i64 0, i64 2
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[COND:%.*]], ptr [[ALLOCA]], ptr [[GEP]]
-; CHECK-NEXT:    [[GEP2:%.*]] = getelementptr inbounds i8, ptr [[SEL]], i64 4
-; CHECK-NEXT:    [[LOAD:%.*]] = load i8, ptr [[GEP2]], align 1
-; CHECK-NEXT:    ret i8 [[LOAD]]
+; CHECK-NOT:     [[ALLOCA:%.*]] = alloca [32 x i8]
+; CHECK-NEXT:    ret i8 0
 ;
 entry:
   %alloca = alloca [32 x i8]
Index: llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -72,14 +72,14 @@
         continue;
       }
 
-      if (isa<PHINode>(I)) {
+      if (isa<PHINode, SelectInst>(I)) {
         // We set IsOffset=true, to forbid the memcpy from occurring after the
         // phi: If one of the phi operands is not based on the alloca, we
         // would incorrectly omit a write.
         Worklist.emplace_back(I, true);
         continue;
       }
-      if (isa<BitCastInst>(I) || isa<AddrSpaceCastInst>(I)) {
+      if (isa<BitCastInst, AddrSpaceCastInst>(I)) {
         // If uses of the bitcast are ok, we are ok.
         Worklist.emplace_back(I, IsOffset);
         continue;
@@ -320,6 +320,19 @@
       Worklist.insert(PHI);
       if (!collectUsersRecursive(*PHI))
         return false;
+    } else if (auto *SI = dyn_cast<SelectInst>(Inst)) {
+      if (!isa<Instruction>(SI->getTrueValue()) ||
+          !isa<Instruction>(SI->getFalseValue()))
+        return false;
+
+      if (!isAvailable(cast<Instruction>(SI->getTrueValue())) ||
+          !isAvailable(cast<Instruction>(SI->getFalseValue()))) {
+        ValuesToRevisit.insert(Inst);
+        continue;
+      }
+      Worklist.insert(SI);
+      if (!collectUsersRecursive(*SI))
+        return false;
     } else if (isa<GetElementPtrInst, BitCastInst>(Inst)) {
       Worklist.insert(Inst);
       if (!collectUsersRecursive(*Inst))
@@ -385,6 +398,13 @@
     IC.InsertNewInstWith(NewI, *BC);
     NewI->takeName(BC);
     WorkMap[BC] = NewI;
+  } else if (auto *SI = dyn_cast<SelectInst>(I)) {
+    auto *NewSI = SelectInst::Create(
+        SI->getCondition(), getReplacement(SI->getTrueValue()),
+        getReplacement(SI->getFalseValue()), SI->getName(), nullptr, SI);
+    IC.InsertNewInstWith(NewSI, *SI);
+    NewSI->takeName(SI);
+    WorkMap[SI] = NewSI;
   } else if (auto *MemCpy = dyn_cast<MemTransferInst>(I)) {
     auto *SrcV = getReplacement(MemCpy->getRawSource());
     // The pointer may appear in the destination of a copy, but we don't want to


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