[PATCH] D153511: [BasicAA] Don't short-circuit non-capturing arguments

[Nikita Popov via Phabricator via llvm-commits]

nikic updated this revision to Diff 533891.
nikic added a comment.

Update comment, remove FIXME.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D153511/new/

https://reviews.llvm.org/D153511

Files:
  llvm/lib/Analysis/BasicAliasAnalysis.cpp
  llvm/test/Transforms/PhaseOrdering/dse-ephemeral-value-captures.ll


Index: llvm/test/Transforms/PhaseOrdering/dse-ephemeral-value-captures.ll
===================================================================
--- llvm/test/Transforms/PhaseOrdering/dse-ephemeral-value-captures.ll
+++ llvm/test/Transforms/PhaseOrdering/dse-ephemeral-value-captures.ll
@@ -22,11 +22,16 @@
   ret i1 0
 }
 
-; FIXME: At the moment, the function is incorrectly simplified to unreachable.
 define i32 @test() {
 ; CHECK-LABEL: define i32 @test() {
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    unreachable
+; CHECK-NEXT:    br label [[THEN_I:%.*]]
+; CHECK:       then.i:
+; CHECK-NEXT:    [[RES_I:%.*]] = call i1 @cond()
+; CHECK-NEXT:    br label [[CHECK_COND_EXIT:%.*]]
+; CHECK:       check_cond.exit:
+; CHECK-NEXT:    call void @llvm.assume(i1 [[RES_I]])
+; CHECK-NEXT:    ret i32 0
 ;
 entry:
   %a = alloca i32, align 4
Index: llvm/lib/Analysis/BasicAliasAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -864,9 +864,11 @@
     if (!AI->isStaticAlloca() && isIntrinsicCall(Call, Intrinsic::stackrestore))
       return ModRefInfo::Mod;
 
-  // If the pointer is to a locally allocated object that does not escape,
-  // then the call can not mod/ref the pointer unless the call takes the pointer
-  // as an argument, and itself doesn't capture it.
+  // A call can access a locally allocated object either because it is passed as
+  // an argument to the call, or because it has escaped prior to the call.
+  //
+  // Make sure the object has not escaped here, and then check that none of the
+  // call arguments alias the object below.
   if (!isa<Constant>(Object) && Call != Object &&
       AAQI.CI->isNotCapturedBeforeOrAt(Object, Call)) {
 
@@ -877,12 +879,7 @@
     unsigned OperandNo = 0;
     for (auto CI = Call->data_operands_begin(), CE = Call->data_operands_end();
          CI != CE; ++CI, ++OperandNo) {
-      // Only look at the no-capture or byval pointer arguments.  If this
-      // pointer were passed to arguments that were neither of these, then it
-      // couldn't be no-capture.
-      if (!(*CI)->getType()->isPointerTy() ||
-          (!Call->doesNotCapture(OperandNo) && OperandNo < Call->arg_size() &&
-           !Call->isByValArgument(OperandNo)))
+      if (!(*CI)->getType()->isPointerTy())
         continue;
 
       // Call doesn't access memory through this operand, so we don't care


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