[llvm] r282150 - [RS4GC] Remat in presence of phi and use live value

[Anna Thomas via llvm-commits]

Author: annat
Date: Thu Sep 22 08:13:06 2016
New Revision: 282150

URL: http://llvm.org/viewvc/llvm-project?rev=282150&view=rev
Log:
[RS4GC] Remat in presence of phi and use live value

Summary:

Reviewers:

Subscribers:

Modified:
    llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
    llvm/trunk/test/Transforms/RewriteStatepointsForGC/rematerialize-derived-pointers.ll

Modified: llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp?rev=282150&r1=282149&r2=282150&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp Thu Sep 22 08:13:06 2016
@@ -1976,7 +1976,8 @@ static void rematerializeLiveValues(Call
     // Utility function which clones all instructions from "ChainToBase"
     // and inserts them before "InsertBefore". Returns rematerialized value
     // which should be used after statepoint.
-    auto rematerializeChain = [&ChainToBase](Instruction *InsertBefore) {
+    auto rematerializeChain = [&ChainToBase](
+        Instruction *InsertBefore, Value *RootOfChain, Value *AlternateLiveBase) {
       Instruction *LastClonedValue = nullptr;
       Instruction *LastValue = nullptr;
       for (Instruction *Instr: ChainToBase) {
@@ -1996,13 +1997,24 @@ static void rematerializeLiveValues(Call
           assert(LastValue);
           ClonedValue->replaceUsesOfWith(LastValue, LastClonedValue);
 #ifndef NDEBUG
-          // Assert that cloned instruction does not use any instructions from
-          // this chain other than LastClonedValue
           for (auto OpValue : ClonedValue->operand_values()) {
+            // Assert that cloned instruction does not use any instructions from
+            // this chain other than LastClonedValue
             assert(!is_contained(ChainToBase, OpValue) &&
                    "incorrect use in rematerialization chain");
+            // Assert that the cloned instruction does not use the RootOfChain
+            // or the AlternateLiveBase.
+            assert(OpValue != RootOfChain && OpValue != AlternateLiveBase);
           }
 #endif
+        } else {
+          // For the first instruction, replace the use of unrelocated base i.e.
+          // RootOfChain/OrigRootPhi, with the corresponding PHI present in the
+          // live set. They have been proved to be the same PHI nodes.  Note
+          // that the *only* use of the RootOfChain in the ChainToBase list is
+          // the first Value in the list.
+          if (RootOfChain != AlternateLiveBase)
+            ClonedValue->replaceUsesOfWith(RootOfChain, AlternateLiveBase);
         }
 
         LastClonedValue = ClonedValue;
@@ -2017,7 +2029,8 @@ static void rematerializeLiveValues(Call
     if (CS.isCall()) {
       Instruction *InsertBefore = CS.getInstruction()->getNextNode();
       assert(InsertBefore);
-      Instruction *RematerializedValue = rematerializeChain(InsertBefore);
+      Instruction *RematerializedValue = rematerializeChain(
+          InsertBefore, RootOfChain, Info.PointerToBase[LiveValue]);
       Info.RematerializedValues[RematerializedValue] = LiveValue;
     } else {
       InvokeInst *Invoke = cast<InvokeInst>(CS.getInstruction());
@@ -2027,10 +2040,10 @@ static void rematerializeLiveValues(Call
       Instruction *UnwindInsertBefore =
           &*Invoke->getUnwindDest()->getFirstInsertionPt();
 
-      Instruction *NormalRematerializedValue =
-          rematerializeChain(NormalInsertBefore);
-      Instruction *UnwindRematerializedValue =
-          rematerializeChain(UnwindInsertBefore);
+      Instruction *NormalRematerializedValue = rematerializeChain(
+          NormalInsertBefore, RootOfChain, Info.PointerToBase[LiveValue]);
+      Instruction *UnwindRematerializedValue = rematerializeChain(
+          UnwindInsertBefore, RootOfChain, Info.PointerToBase[LiveValue]);
 
       Info.RematerializedValues[NormalRematerializedValue] = LiveValue;
       Info.RematerializedValues[UnwindRematerializedValue] = LiveValue;

Modified: llvm/trunk/test/Transforms/RewriteStatepointsForGC/rematerialize-derived-pointers.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/RewriteStatepointsForGC/rematerialize-derived-pointers.ll?rev=282150&r1=282149&r2=282150&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/RewriteStatepointsForGC/rematerialize-derived-pointers.ll (original)
+++ llvm/trunk/test/Transforms/RewriteStatepointsForGC/rematerialize-derived-pointers.ll Thu Sep 22 08:13:06 2016
@@ -285,7 +285,7 @@ merge:
   ; CHECK: %statepoint_token = call token (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint
   ; CHECK: %basephi.base.relocated = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(token %statepoint_token, i32 7, i32 7) ; (%basephi.base, %basephi.base)
   ; CHECK: %basephi.base.relocated.casted = bitcast i8 addrspace(1)* %basephi.base.relocated to i32 addrspace(1)*
-  ; CHECK: %ptr.gep.remat = getelementptr i32, i32 addrspace(1)* %basephi, i32 15
+  ; CHECK: %ptr.gep.remat = getelementptr i32, i32 addrspace(1)* %basephi.base.relocated.casted, i32 15
   ; CHECK: call void @use_obj32(i32 addrspace(1)* %ptr.gep.remat)
 
 
@@ -296,3 +296,35 @@ merge:
   call void @use_obj32(i32 addrspace(1)* %ptr.gep)
   ret void
 }
+
+
+define void @test_intersecting_chains_with_phi(i1 %cond) gc "statepoint-example" {
+; CHECK-LABEL: test_intersecting_chains_with_phi
+entry:
+  %base1 = call i32 addrspace(1)* @new_instance()
+  %base2 = call i32 addrspace(1)* @new_instance()
+  br i1 %cond, label %here, label %there
+
+here:
+  br label %merge
+
+there:
+  br label %merge
+
+merge:
+  %basephi = phi i32 addrspace(1)* [ %base1, %here ], [ %base2, %there ]
+  %ptr.gep = getelementptr i32, i32 addrspace(1)* %basephi, i32 15
+  %ptr.cast = bitcast i32 addrspace(1)* %ptr.gep to i64 addrspace(1)*
+  %ptr.cast2 = bitcast i32 addrspace(1)* %ptr.gep to i16 addrspace(1)*
+  call void @do_safepoint() [ "deopt"() ]
+  ; CHECK: statepoint
+  ; CHECK: %ptr.gep.remat1 = getelementptr i32, i32 addrspace(1)* %basephi.base.relocated.casted, i32 15
+  ; CHECK: %ptr.cast.remat = bitcast i32 addrspace(1)* %ptr.gep.remat1 to i64 addrspace(1)*
+  ; CHECK: %ptr.gep.remat = getelementptr i32, i32 addrspace(1)* %basephi.base.relocated.casted, i32 15
+  ; CHECK: %ptr.cast2.remat = bitcast i32 addrspace(1)* %ptr.gep.remat to i16 addrspace(1)*
+  ; CHECK: call void @use_obj64(i64 addrspace(1)* %ptr.cast.remat)
+  ; CHECK: call void @use_obj16(i16 addrspace(1)* %ptr.cast2.remat)
+  call void @use_obj64(i64 addrspace(1)* %ptr.cast)
+  call void @use_obj16(i16 addrspace(1)* %ptr.cast2)
+  ret void
+}