[PATCH] D84432: [IPSCCP] Drop argmemonly after replacing pointer argument.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: efriedma, davide, nikic, jdoerfert.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

This patch updates IPSCCP to drop argmemonly and
inaccessiblemem_or_argmemonly if it replaces a pointer argument.

Fixes PR46717.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D84432

Files:
  llvm/lib/Transforms/Scalar/SCCP.cpp
  llvm/test/Transforms/SCCP/ipscp-drop-argmemonly.ll


Index: llvm/test/Transforms/SCCP/ipscp-drop-argmemonly.ll
===================================================================
--- llvm/test/Transforms/SCCP/ipscp-drop-argmemonly.ll
+++ llvm/test/Transforms/SCCP/ipscp-drop-argmemonly.ll
@@ -11,7 +11,7 @@
 ; Here the pointer argument %arg will be replaced by a constant. We need to
 ; drop argmemonly.
 define internal void @ptrarg.1(i32* %arg, i32 %val) argmemonly nounwind {
-; CHECK: Function Attrs: argmemonly nounwind
+; CHECK: Function Attrs: nounwind
 ; CHECK-LABEL: @ptrarg.1(
 ; CHECK-NEXT:    store i32 10, i32* @g, align 4
 ; CHECK-NEXT:    ret void
@@ -59,7 +59,7 @@
 ; Here the pointer argument %arg will be replaced by a constant. We need to
 ; drop inaccessiblemem_or_argmemonly.
 define internal void @ptrarg.3(i32* %arg, i32 %val) inaccessiblemem_or_argmemonly nounwind {
-; CHECK: Function Attrs: inaccessiblemem_or_argmemonly nounwind
+; CHECK: Function Attrs: nounwind
 ; CHECK-LABEL: @ptrarg.3(
 ; CHECK-NEXT:    store i32 10, i32* @g, align 4
 ; CHECK-NEXT:    ret void
@@ -107,7 +107,7 @@
 ; Here the pointer argument %arg will be replaced by a constant. We need to
 ; drop inaccessiblemem_or_argmemonly.
 define internal void @ptrarg.5(i32* %arg, i32 %val) argmemonly inaccessiblemem_or_argmemonly nounwind {
-; CHECK: Function Attrs: argmemonly inaccessiblemem_or_argmemonly nounwind
+; CHECK: Function Attrs: nounwind
 ; CHECK-LABEL: @ptrarg.5(
 ; CHECK-NEXT:    store i32 10, i32* @g, align 4
 ; CHECK-NEXT:    ret void
Index: llvm/lib/Transforms/Scalar/SCCP.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/SCCP.cpp
+++ llvm/lib/Transforms/Scalar/SCCP.cpp
@@ -1911,15 +1911,23 @@
 
     SmallVector<BasicBlock *, 512> BlocksToErase;
 
-    if (Solver.isBlockExecutable(&F.front()))
-      for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;
-           ++AI) {
-        if (!AI->use_empty() && tryToReplaceWithConstant(Solver, &*AI)) {
+    if (Solver.isBlockExecutable(&F.front())) {
+      bool ReplacedPointerArg = false;
+      for (Argument &Arg : F.args()) {
+        if (!Arg.use_empty() && tryToReplaceWithConstant(Solver, &Arg)) {
+          ReplacedPointerArg |= Arg.getType()->isPointerTy();
           ++IPNumArgsElimed;
-          continue;
         }
       }
 
+      // If we replaced an argument, argmemonly and
+      // inaccessiblemem_or_argmemonly do not hold any longer. Remove them.
+      if (ReplacedPointerArg) {
+        F.removeFnAttr(Attribute::ArgMemOnly);
+        F.removeFnAttr(Attribute::InaccessibleMemOrArgMemOnly);
+      }
+    }
+
     SmallPtrSet<Value *, 32> InsertedValues;
     for (BasicBlock &BB : F) {
       if (!Solver.isBlockExecutable(&BB)) {


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