[PATCH] D84220: [IPSCCP] Fix a bug that the "returned" attribute is not cleared when function is optimized to return undef

[Congzhe Cao via Phabricator via llvm-commits]

congzhe updated this revision to Diff 282339.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D84220/new/

https://reviews.llvm.org/D84220

Files:
  llvm/lib/Transforms/Scalar/SCCP.cpp
  llvm/test/Transforms/SCCP/ipsccp-clear-returned.ll


Index: llvm/test/Transforms/SCCP/ipsccp-clear-returned.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/SCCP/ipsccp-clear-returned.ll
@@ -0,0 +1,24 @@
+; if IPSCCP determines a function returns undef,
+; then the "returned" attribute of input arguments
+; should be cleared.
+
+; RUN: opt < %s -ipsccp -S | FileCheck %s
+define i32 @main() {
+; CHECK-LABEL: @main
+entry:
+; CHECK-NEXT: entry:
+  %call = call i32 @func_return_undef(i32 returned 1)
+; CHECK: call i32 @func_return_undef(i32 1)
+; CHECK-NOT: returned
+  ret i32 %call
+; CHECK: ret i32 1
+}
+
+define internal i32 @func_return_undef(i32 returned %arg) {
+; CHECK: {{define.*@func_return_undef}}
+; CHECK-NOT: returned
+entry:
+; CHECK-NEXT: entry:
+; CHECK-NEXT: {{ret.*undef}}
+ret i32 %arg
+}
Index: llvm/lib/Transforms/Scalar/SCCP.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/SCCP.cpp
+++ llvm/lib/Transforms/Scalar/SCCP.cpp
@@ -33,6 +33,7 @@
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/ValueLattice.h"
 #include "llvm/Analysis/ValueLatticeUtils.h"
+#include "llvm/IR/AbstractCallSite.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/Constants.h"
@@ -2035,11 +2036,29 @@
   }
 
   // Zap all returns which we've identified as zap to change.
+  SmallPtrSet<Function*, 8> FuncZappedReturn;
   for (unsigned i = 0, e = ReturnsToZap.size(); i != e; ++i) {
     Function *F = ReturnsToZap[i]->getParent()->getParent();
     ReturnsToZap[i]->setOperand(0, UndefValue::get(F->getReturnType()));
+    // Record all functions that are zapped
+    if (FuncZappedReturn.find(F) == FuncZappedReturn.end())
+      FuncZappedReturn.insert(F);
+  }
+
+  // Remove the returned attribute for zapped functions and the
+  // corresponding call sites
+  for (Function *F : FuncZappedReturn) {
+    for (Argument &A : F->args())
+      F->removeParamAttr(A.getArgNo(), Attribute::Returned);
+    for (Use &U : F->uses()) {
+      CallBase *CB = dyn_cast<CallBase>(U.getUser());
+      if (!CB)
+        continue;
+      for (auto &arg : CB->args()) {
+        CB->removeParamAttr(CB->getArgOperandNo(&arg), Attribute::Returned);
+      }
+    }
   }
-
   // If we inferred constant or undef values for globals variables, we can
   // delete the global and any stores that remain to it.
   for (auto &I : make_early_inc_range(Solver.getTrackedGlobals())) {


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