[PATCH] D21249: InstCombine: Don't strip convergent from intrinsic callsites

[Matt Arsenault via llvm-commits]

arsenm created this revision.
arsenm added a subscriber: llvm-commits.

Specific instances of intrinsic calls may want to be convergent, such as certain register reads but the intrinsic declaration is not.


http://reviews.llvm.org/D21249

Files:
  lib/Transforms/InstCombine/InstCombineCalls.cpp
  test/Transforms/InstCombine/convergent.ll

Index: test/Transforms/InstCombine/convergent.ll
===================================================================
--- test/Transforms/InstCombine/convergent.ll
+++ test/Transforms/InstCombine/convergent.ll
@@ -3,6 +3,8 @@
 declare i32 @k() convergent
 declare i32 @f()
 
+declare i64 @llvm.read_register.i64(metadata) nounwind
+
 define i32 @extern() {
   ; Convergent attr shouldn't be removed here; k is convergent.
   ; CHECK: call i32 @k() [[CONVERGENT_ATTR:#[0-9]+]]
@@ -30,4 +32,13 @@
   ret i32 %a
 }
 
+; do not remove from convergent intrinsic call sites
+; CHECK-LABEL: @convergent_intrinsic_call(
+; CHECK: call i64 @llvm.read_register.i64(metadata !0) [[CONVERGENT_ATTR]]
+define i64 @convergent_intrinsic_call() {
+  %val = call i64 @llvm.read_register.i64(metadata !0) convergent
+  ret i64 %val
+}
+
 ; CHECK: [[CONVERGENT_ATTR]] = { convergent }
+!0 = !{!"foo"}
Index: lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2507,7 +2507,8 @@
 
   if (Function *CalleeF = dyn_cast<Function>(Callee)) {
     // Remove the convergent attr on calls when the callee is not convergent.
-    if (CS.isConvergent() && !CalleeF->isConvergent()) {
+    if (CS.isConvergent() && !CalleeF->isConvergent() &&
+        !CalleeF->isIntrinsic()) {
       DEBUG(dbgs() << "Removing convergent attr from instr "
                    << CS.getInstruction() << "\n");
       CS.setNotConvergent();


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