[llvm] r372771 - [GCRelocate] Add a peephole to canonicalize base pointer relocation

[Philip Reames via llvm-commits]

Author: reames
Date: Tue Sep 24 10:24:16 2019
New Revision: 372771

URL: http://llvm.org/viewvc/llvm-project?rev=372771&view=rev
Log:
[GCRelocate] Add a peephole to canonicalize base pointer relocation

If we generate the gc.relocate, and then later prove two arguments to the statepoint are equivalent, we should canonicalize the gc.relocate to the form we would have produced if this had been known before rewriting.


Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
    llvm/trunk/test/Transforms/InstCombine/gc.relocate.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp?rev=372771&r1=372770&r2=372771&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Tue Sep 24 10:24:16 2019
@@ -3951,10 +3951,21 @@ Instruction *InstCombiner::visitCallInst
     break;
   }
   case Intrinsic::experimental_gc_relocate: {
+    auto &GCR = *cast<GCRelocateInst>(II);
+
+    // If we have two copies of the same pointer in the statepoint argument
+    // list, canonicalize to one.  This may let us common gc.relocates.
+    if (GCR.getBasePtr() == GCR.getDerivedPtr() &&
+        GCR.getBasePtrIndex() != GCR.getDerivedPtrIndex()) {
+      auto *OpIntTy = GCR.getOperand(2)->getType();
+      II->setOperand(2, ConstantInt::get(OpIntTy, GCR.getBasePtrIndex()));
+      return II;
+    }
+    
     // Translate facts known about a pointer before relocating into
     // facts about the relocate value, while being careful to
     // preserve relocation semantics.
-    Value *DerivedPtr = cast<GCRelocateInst>(II)->getDerivedPtr();
+    Value *DerivedPtr = GCR.getDerivedPtr();
 
     // Remove the relocation if unused, note that this check is required
     // to prevent the cases below from looping forever.

Modified: llvm/trunk/test/Transforms/InstCombine/gc.relocate.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/gc.relocate.ll?rev=372771&r1=372770&r2=372771&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/gc.relocate.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/gc.relocate.ll Tue Sep 24 10:24:16 2019
@@ -52,6 +52,17 @@ entry:
   ret <2 x i8 addrspace(1)*> %obj.relocated
 }
 
+define i32 addrspace(1)* @canonical_base(i32 addrspace(1)* %dparam) gc "statepoint-example" {
+; Checks that a nonnull pointer
+; CHECK-LABEL: @canonical_base
+; CHECK: (token %tok, i32 7, i32 7) ; (%dparam, %dparam)
+entry:
+  %tok = tail call token (i64, i32, i1 ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_i1f(i64 0, i32 0, i1 ()* @return_i1, i32 0, i32 0, i32 0, i32 0, i32 addrspace(1)* %dparam, i32 addrspace(1)* %dparam)
+  %relocate = call i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(token %tok,  i32 7, i32 8)
+  ret i32 addrspace(1)* %relocate
+}
+
+
 declare void @do_safepoint()
 
 declare token @llvm.experimental.gc.statepoint.p0f_isVoidf(i64, i32, void ()*, i32, i32, ...)