[PATCH] D75598: [InstCombine] Handle gc.relocate(null) in one iteration

[Serguei Katkov via Phabricator via llvm-commits]

skatkov updated this revision to Diff 248132.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D75598/new/

https://reviews.llvm.org/D75598

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
  llvm/test/Transforms/InstCombine/statepoint-null.ll


Index: llvm/test/Transforms/InstCombine/statepoint-null.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/statepoint-null.ll
@@ -0,0 +1,33 @@
+; RUN: opt < %s -instcombine -instcombine-max-iterations=1 -S | FileCheck %s
+; These tests check the optimizations specific to
+; pointers being relocated at a statepoint.
+
+
+declare void @func()
+
+define i1 @test_null(i1 %cond) gc "statepoint-example" {
+entry:
+  br i1 %cond, label %left, label %right
+
+right:
+  br label %merge
+
+left:
+  %safepoint_token = tail call token (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 0, i32 0, void ()* @func, i32 0, i32 0, i32 0, i32 0, i32 addrspace(1)* null)
+  %pnew = call i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(token %safepoint_token,  i32 7, i32 7)
+  br label %merge
+
+merge:
+  %pnew_phi = phi i32 addrspace(1)* [null, %right], [%pnew, %left]
+  %safepoint_token2 = tail call token (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 0, i32 0, void ()* @func, i32 0, i32 0, i32 0, i32 0, i32 addrspace(1)* %pnew_phi)
+  %pnew2 = call i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(token %safepoint_token2,  i32 7, i32 7)
+  %cmp = icmp eq i32 addrspace(1)* %pnew2, null
+  ret i1 %cmp
+; CHECK-LABEL: test_null
+; CHECK-NOT: %pnew
+; CHECK-NOT: %pnew2
+; CHECK: ret i1 true
+}
+
+declare token @llvm.experimental.gc.statepoint.p0f_isVoidf(i64, i32, void ()*, i32, i32, ...)
+declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(token, i32, i32) #3
Index: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -4375,6 +4375,26 @@
 
 /// Improvements for call, callbr and invoke instructions.
 Instruction *InstCombiner::visitCallBase(CallBase &Call) {
+  // Special handling of statepoint intrinsic.
+  // Let's we have the following case:
+  // A = gc.relocate(null)
+  // B = statepoint(A)
+  // C = gc.relocate(A)
+  // A will be substituted with null and its user B will be added to worklist.
+  // Statepoint B is not simplified and if C was considered before it will be
+  // re-considered after simplification of A.
+  // To resolve this case while processing statepoint B we add all gc.relocate
+  // users to worklist if they can be simplified to null.
+  // This is mostly to save compile time. Actually C can be transformed on
+  // the next iteration if InstCombine while we want to handle all gc.relocate
+  // chains in one iteraton.
+  if (isStatepoint(Call))
+    for (User *U : Call.users())
+      if (auto *GCR = dyn_cast<GCRelocateInst>(U))
+        if (isa<PointerType>(U->getType()))
+          if (isa<ConstantPointerNull>(GCR->getDerivedPtr()))
+            Worklist.add(GCR);
+
   if (isAllocationFn(&Call, &TLI))
     annotateAnyAllocSite(Call, &TLI);
 


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