[PATCH] D93991: [ArgPromotion] Delay dead GEP removal until doPromotion.

[Florian Hahn via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rGe0905553b424: [ArgPromotion] Delay dead GEP removal until doPromotion. (authored by fhahn).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D93991/new/

https://reviews.llvm.org/D93991

Files:
  llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
  llvm/test/Transforms/ArgumentPromotion/dead-gep-no-promotion.ll


Index: llvm/test/Transforms/ArgumentPromotion/dead-gep-no-promotion.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/ArgumentPromotion/dead-gep-no-promotion.ll
@@ -0,0 +1,30 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -argpromotion -S %s | FileCheck %s
+
+ at glob = external global i32*
+
+; No arguments in @callee can be promoted, but it contains a dead GEP. Make
+; sure it is not removed, as we do not perform any promotion.
+define i32 @caller(i32* %ptr) {
+; CHECK-LABEL: @caller(
+; CHECK-NEXT:    call void @callee(i32* [[PTR:%.*]], i32* [[PTR]], i32* [[PTR]])
+; CHECK-NEXT:    ret i32 0
+;
+  call void @callee(i32* %ptr, i32* %ptr, i32* %ptr)
+  ret i32 0
+}
+
+define internal void @callee(i32* %arg, i32* %arg1, i32* %arg2) {
+; CHECK-LABEL: define internal void @callee(
+; CHECK-NEXT:    call void @external_fn(i32* [[ARG:%.*]], i32* [[ARG1:%.*]])
+; CHECK-NEXT:    [[DEAD_GEP:%.*]] = getelementptr inbounds i32, i32* [[ARG1]], i32 17
+; CHECK-NEXT:    store i32* [[ARG2:%.*]], i32** @glob, align 8
+; CHECK-NEXT:    ret void
+;
+  call void @external_fn(i32* %arg, i32* %arg1)
+  %dead.gep = getelementptr inbounds i32, i32* %arg1, i32 17
+  store i32* %arg2, i32** @glob, align 8
+  ret  void
+}
+
+declare void @external_fn(i32*, i32*)
Index: llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
===================================================================
--- llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
+++ llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
@@ -160,13 +160,19 @@
       // In this table, we will track which indices are loaded from the argument
       // (where direct loads are tracked as no indices).
       ScalarizeTable &ArgIndices = ScalarizedElements[&*I];
-      for (User *U : I->users()) {
-        Instruction *UI = cast<Instruction>(U);
+      for (auto Iter = I->user_begin(), End = I->user_end(); Iter != End;) {
+        Instruction *UI = cast<Instruction>(*Iter++);
         Type *SrcTy;
         if (LoadInst *L = dyn_cast<LoadInst>(UI))
           SrcTy = L->getType();
         else
           SrcTy = cast<GetElementPtrInst>(UI)->getSourceElementType();
+        // Skip dead GEPs and remove them.
+        if (isa<GetElementPtrInst>(UI) && UI->use_empty()) {
+          UI->eraseFromParent();
+          continue;
+        }
+
         IndicesVector Indices;
         Indices.reserve(UI->getNumOperands() - 1);
         // Since loads will only have a single operand, and GEPs only a single
@@ -436,6 +442,8 @@
                           << "' in function '" << F->getName() << "'\n");
       } else {
         GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->user_back());
+        assert(!GEP->use_empty() &&
+               "GEPs without uses should be cleaned up already");
         IndicesVector Operands;
         Operands.reserve(GEP->getNumIndices());
         for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
@@ -674,11 +682,7 @@
       if (GEP->use_empty()) {
         // Dead GEP's cause trouble later.  Just remove them if we run into
         // them.
-        GEP->eraseFromParent();
-        // TODO: This runs the above loop over and over again for dead GEPs
-        // Couldn't we just do increment the UI iterator earlier and erase the
-        // use?
-        return isSafeToPromoteArgument(Arg, ByValTy, AAR, MaxElements);
+        continue;
       }
 
       if (!UpdateBaseTy(GEP->getSourceElementType()))


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