[llvm] r251957 - [CodegenPrepare] Do not rematerialize gc.relocates across different basic blocks

[Igor Laevsky via llvm-commits]

Author: igor.laevsky
Date: Tue Nov  3 12:37:40 2015
New Revision: 251957

URL: http://llvm.org/viewvc/llvm-project?rev=251957&view=rev
Log:
[CodegenPrepare] Do not rematerialize gc.relocates across different basic blocks

Differential Revision: http://reviews.llvm.org/D14258


Modified:
    llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
    llvm/trunk/test/Transforms/CodeGenPrepare/statepoint-relocate.ll

Modified: llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp?rev=251957&r1=251956&r2=251957&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp (original)
+++ llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp Tue Nov  3 12:37:40 2015
@@ -589,6 +589,14 @@ simplifyRelocatesOffABase(IntrinsicInst
       continue;
     }
 
+    if (RelocatedBase->getParent() != ToReplace->getParent()) {
+      // Base and derived relocates are in different basic blocks.
+      // In this case transform is only valid when base dominates derived
+      // relocate. However it would be too expensive to check dominance
+      // for each such relocate, so we skip the whole transformation.
+      continue;
+    }
+
     Value *Base = ThisRelocate.getBasePtr();
     auto Derived = dyn_cast<GetElementPtrInst>(ThisRelocate.getDerivedPtr());
     if (!Derived || Derived->getPointerOperand() != Base)

Modified: llvm/trunk/test/Transforms/CodeGenPrepare/statepoint-relocate.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/CodeGenPrepare/statepoint-relocate.ll?rev=251957&r1=251956&r2=251957&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/CodeGenPrepare/statepoint-relocate.ll (original)
+++ llvm/trunk/test/Transforms/CodeGenPrepare/statepoint-relocate.ll Tue Nov  3 12:37:40 2015
@@ -83,6 +83,45 @@ entry:
        ret i32 %ret
 }
 
+define i32 @test_sor_basic_wrong_order(i32* %base) gc "statepoint-example" {
+; CHECK-LABEL: @test_sor_basic_wrong_order
+; Here we have base relocate inserted after derived. Make sure that we don't
+; produce uses of the relocated base pointer before it's definition.
+entry:
+       %ptr = getelementptr i32, i32* %base, i32 15
+       ; CHECK: getelementptr i32, i32* %base, i32 15
+       %tok = call i32 (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* %base, i32* %ptr)
+       %ptr-new = call i32* @llvm.experimental.gc.relocate.p0i32(i32 %tok, i32 7, i32 8)
+       %base-new = call i32* @llvm.experimental.gc.relocate.p0i32(i32 %tok,  i32 7, i32 7)
+       ; CHECK: %base-new = call i32* @llvm.experimental.gc.relocate.p0i32(i32 %tok,  i32 7, i32 7)
+       ; CHECK-NEXT: getelementptr i32, i32* %base-new, i32 15
+       %ret = load i32, i32* %ptr-new
+       ret i32 %ret
+}
+
+define i32 @test_sor_noop_cross_bb(i1 %external-cond, i32* %base) gc "statepoint-example" {
+; CHECK-LABEL: @test_sor_noop_cross_bb
+; Here base relocate doesn't dominate derived relocate. Make sure that we don't
+; produce undefined use of the relocated base pointer.
+entry:
+       %ptr = getelementptr i32, i32* %base, i32 15
+       ; CHECK: getelementptr i32, i32* %base, i32 15
+       %tok = call i32 (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* %base, i32* %ptr)
+       br i1 %external-cond, label %left, label %right
+
+left:
+       %ptr-new = call i32* @llvm.experimental.gc.relocate.p0i32(i32 %tok, i32 7, i32 8)
+       ; CHECK: call i32* @llvm.experimental.gc.relocate.p0i32(i32 %tok, i32 7, i32 8)
+       %ret-new = load i32, i32* %ptr-new
+       ret i32 %ret-new
+
+right:
+       %ptr-base = call i32* @llvm.experimental.gc.relocate.p0i32(i32 %tok, i32 7, i32 7)
+       ; CHECK: call i32* @llvm.experimental.gc.relocate.p0i32(i32 %tok, i32 7, i32 7)
+       %ret-base = load i32, i32* %ptr-base
+       ret i32 %ret-base
+}
+
 declare i32 @llvm.experimental.gc.statepoint.p0f_i1f(i64, i32, i1 ()*, i32, i32, ...)
 declare i32* @llvm.experimental.gc.relocate.p0i32(i32, i32, i32)
 declare [3 x i32]* @llvm.experimental.gc.relocate.p0a3i32(i32, i32, i32)