[llvm] c0ab901 - [Attributor] Selectively look at the callee even when there are operand bundles

[Johannes Doerfert via llvm-commits]

Author: Johannes Doerfert
Date: 2020-09-09T00:52:17-05:00
New Revision: c0ab901bddd5cb80c71848a426b7eaa2882b2ef5

URL: https://github.com/llvm/llvm-project/commit/c0ab901bddd5cb80c71848a426b7eaa2882b2ef5
DIFF: https://github.com/llvm/llvm-project/commit/c0ab901bddd5cb80c71848a426b7eaa2882b2ef5.diff

LOG: [Attributor] Selectively look at the callee even when there are operand bundles

While operand bundles carry unpredictable semantics, we know some of
them and can therefore "ignore" them. In this case we allow to look at
the declaration of `llvm.assume` when asked for the attributes at a call
site. The assume operand bundles we have do not invalidate the
declaration attributes.

We cannot test this in isolation because the llvm.assume attributes are
determined by the parser. However, a follow up patch will provide test
coverage.

Added: 
    

Modified: 
    llvm/lib/Transforms/IPO/Attributor.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
index 2a15c6f0b818..4fcea9b5355d 100644
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -325,6 +325,13 @@ const IRPosition
 SubsumingPositionIterator::SubsumingPositionIterator(const IRPosition &IRP) {
   IRPositions.emplace_back(IRP);
 
+  // Helper to determine if operand bundles on a call site are benin or
+  // potentially problematic. We handle only llvm.assume for now.
+  auto CanIgnoreOperandBundles = [](const CallBase &CB) {
+    return (isa<IntrinsicInst>(CB) &&
+            cast<IntrinsicInst>(CB).getIntrinsicID() == Intrinsic ::assume);
+  };
+
   const auto *CB = dyn_cast<CallBase>(&IRP.getAnchorValue());
   switch (IRP.getPositionKind()) {
   case IRPosition::IRP_INVALID:
@@ -339,7 +346,7 @@ SubsumingPositionIterator::SubsumingPositionIterator(const IRPosition &IRP) {
     assert(CB && "Expected call site!");
     // TODO: We need to look at the operand bundles similar to the redirection
     //       in CallBase.
-    if (!CB->hasOperandBundles())
+    if (!CB->hasOperandBundles() || CanIgnoreOperandBundles(*CB))
       if (const Function *Callee = CB->getCalledFunction())
         IRPositions.emplace_back(IRPosition::function(*Callee));
     return;
@@ -347,7 +354,7 @@ SubsumingPositionIterator::SubsumingPositionIterator(const IRPosition &IRP) {
     assert(CB && "Expected call site!");
     // TODO: We need to look at the operand bundles similar to the redirection
     //       in CallBase.
-    if (!CB->hasOperandBundles()) {
+    if (!CB->hasOperandBundles() || CanIgnoreOperandBundles(*CB)) {
       if (const Function *Callee = CB->getCalledFunction()) {
         IRPositions.emplace_back(IRPosition::returned(*Callee));
         IRPositions.emplace_back(IRPosition::function(*Callee));
@@ -368,7 +375,7 @@ SubsumingPositionIterator::SubsumingPositionIterator(const IRPosition &IRP) {
     assert(CB && ArgNo >= 0 && "Expected call site!");
     // TODO: We need to look at the operand bundles similar to the redirection
     //       in CallBase.
-    if (!CB->hasOperandBundles()) {
+    if (!CB->hasOperandBundles() || CanIgnoreOperandBundles(*CB)) {
       const Function *Callee = CB->getCalledFunction();
       if (Callee && Callee->arg_size() > unsigned(ArgNo))
         IRPositions.emplace_back(IRPosition::argument(*Callee->getArg(ArgNo)));