[PATCH] D156397: [FunctionAttrs] Unconditionally perform argument attribute inference in the first function-attrs pass

[Changpeng Fang via Phabricator via llvm-commits]

cfang updated this revision to Diff 548345.
cfang added a comment.

update a comment
add pre-commit of the LIT to show the diff from this patch.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D156397/new/

https://reviews.llvm.org/D156397

Files:
  llvm/lib/Transforms/IPO/FunctionAttrs.cpp
  llvm/test/Transforms/InstCombine/unused-nonnull.ll
  llvm/test/Transforms/PhaseOrdering/early-arg-attrs-inference.ll


Index: llvm/test/Transforms/PhaseOrdering/early-arg-attrs-inference.ll
===================================================================
--- llvm/test/Transforms/PhaseOrdering/early-arg-attrs-inference.ll
+++ llvm/test/Transforms/PhaseOrdering/early-arg-attrs-inference.ll
@@ -4,16 +4,13 @@
 define i32 @f(ptr noalias %p, i32 %c) {
 ; CHECK-LABEL: define i32 @f
 ; CHECK-SAME: (ptr noalias nocapture readonly [[P:%.*]], i32 [[C:%.*]]) local_unnamed_addr {
-; CHECK-NEXT:    [[I:%.*]] = load i32, ptr [[P]], align 4
 ; CHECK-NEXT:    tail call void @g()
 ; CHECK-NEXT:    tail call void @g()
 ; CHECK-NEXT:    tail call void @g()
 ; CHECK-NEXT:    tail call void @g()
 ; CHECK-NEXT:    tail call void @g()
 ; CHECK-NEXT:    tail call void @g()
-; CHECK-NEXT:    [[I2:%.*]] = load i32, ptr [[P]], align 4
-; CHECK-NEXT:    [[R:%.*]] = sub i32 [[I]], [[I2]]
-; CHECK-NEXT:    ret i32 [[R]]
+; CHECK-NEXT:    ret i32 0
 ;
   %i = load i32, ptr %p
   call void @g()
Index: llvm/test/Transforms/InstCombine/unused-nonnull.ll
===================================================================
--- llvm/test/Transforms/InstCombine/unused-nonnull.ll
+++ llvm/test/Transforms/InstCombine/unused-nonnull.ll
@@ -9,7 +9,7 @@
 
 define i32 @main(i32 %argc, ptr %argv) #0 {
 ; CHECK-LABEL: define {{[^@]+}}@main
-; CHECK-SAME: (i32 [[ARGC:%.*]], ptr nocapture readnone [[ARGV:%.*]]) local_unnamed_addr #[[ATTR0:[0-9]+]] {
+; CHECK-SAME: (i32 [[ARGC:%.*]], ptr nocapture readonly [[ARGV:%.*]]) local_unnamed_addr #[[ATTR0:[0-9]+]] {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[TMP0:%.*]] = icmp slt i32 [[ARGC]], 2
 ; CHECK-NEXT:    [[SPEC_SELECT:%.*]] = select i1 [[TMP0]], i32 0, i32 [[ARGC]]
Index: llvm/lib/Transforms/IPO/FunctionAttrs.cpp
===================================================================
--- llvm/lib/Transforms/IPO/FunctionAttrs.cpp
+++ llvm/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -1720,7 +1720,8 @@
 
 template <typename AARGetterT>
 static SmallSet<Function *, 8>
-deriveAttrsInPostOrder(ArrayRef<Function *> Functions, AARGetterT &&AARGetter) {
+deriveAttrsInPostOrder(ArrayRef<Function *> Functions, AARGetterT &&AARGetter,
+                       bool ArgAttrsOnly) {
   SCCNodesResult Nodes = createSCCNodeSet(Functions);
 
   // Bail if the SCC only contains optnone functions.
@@ -1728,6 +1729,10 @@
     return {};
 
   SmallSet<Function *, 8> Changed;
+  if (ArgAttrsOnly) {
+    addArgumentAttrs(Nodes.SCCNodes, Changed);
+    return Changed;
+  }
 
   addArgumentReturnedAttrs(Nodes.SCCNodes, Changed);
   addMemoryAttrs(Nodes.SCCNodes, AARGetter, Changed);
@@ -1762,10 +1767,13 @@
                                                   LazyCallGraph &CG,
                                                   CGSCCUpdateResult &) {
   // Skip non-recursive functions if requested.
+  // Only infer argument attributes for non-recursive functions, because
+  // it can affect optimization behavior in conjunction with noalias.
+  bool ArgAttrsOnly = false;
   if (C.size() == 1 && SkipNonRecursive) {
     LazyCallGraph::Node &N = *C.begin();
     if (!N->lookup(N))
-      return PreservedAnalyses::all();
+      ArgAttrsOnly = true;
   }
 
   FunctionAnalysisManager &FAM =
@@ -1782,7 +1790,8 @@
     Functions.push_back(&N.getFunction());
   }
 
-  auto ChangedFunctions = deriveAttrsInPostOrder(Functions, AARGetter);
+  auto ChangedFunctions =
+      deriveAttrsInPostOrder(Functions, AARGetter, ArgAttrsOnly);
   if (ChangedFunctions.empty())
     return PreservedAnalyses::all();
 


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