[PATCH] D15789: [RS4GC] Fix rematerialization of bitcast of bitcast.

[Manuel Jacob via llvm-commits]

mjacob created this revision.
mjacob added reviewers: reames, igor-laevsky.
mjacob added subscribers: llvm-commits, alex.
Herald added a subscriber: sanjoy.

Previously, only the outer (last) bitcast was rematerialized, resulting in a
use of the unrelocated inner (first) bitcast after the statepoint.  See the
test case for an example.

http://reviews.llvm.org/D15789

Files:
  lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
  test/Transforms/RewriteStatepointsForGC/rematerialize-derived-pointers.ll

Index: test/Transforms/RewriteStatepointsForGC/rematerialize-derived-pointers.ll
===================================================================
--- test/Transforms/RewriteStatepointsForGC/rematerialize-derived-pointers.ll
+++ test/Transforms/RewriteStatepointsForGC/rematerialize-derived-pointers.ll
@@ -47,6 +47,22 @@
   ret void
 }
 
+define void @"test_bitcast_bitcast"(i32 addrspace(1)* %base) gc "statepoint-example" {
+; CHECK-LABEL: test_bitcast_bitcast
+entry:
+  %ptr1 = bitcast i32 addrspace(1)* %base to i64 addrspace(1)*
+  %ptr2 = bitcast i64 addrspace(1)* %ptr1 to i16 addrspace(1)*
+  ; CHECK: bitcast i32 addrspace(1)* %base to i64 addrspace(1)*
+  %sp = call token (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 0, i32 0, void ()* @do_safepoint, i32 0, i32 0, i32 0, i32 0)
+  ; CHECK: %base.relocated = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(token %sp, i32 7, i32 7)
+  ; CHECK: %base.relocated.casted = bitcast i8 addrspace(1)* %base.relocated to i32 addrspace(1)*
+  ; CHECK: bitcast i32 addrspace(1)* %base.relocated.casted to i64 addrspace(1)*
+  ; CHECK: bitcast i64 addrspace(1)* %ptr1.remat to i16 addrspace(1)*
+  call void @use_obj32(i32 addrspace(1)* %base)
+  call void @use_obj16(i16 addrspace(1)* %ptr2)
+  ret void
+}
+
 define void @"test_bitcast_gep"(i32 addrspace(1)* %base) gc "statepoint-example" {
 ; CHECK-LABEL: test_bitcast_gep
 entry:
Index: lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
===================================================================
--- lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
+++ lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
@@ -2101,16 +2101,9 @@
   }
 
   if (CastInst *CI = dyn_cast<CastInst>(CurrentValue)) {
-    Value *Def = CI->stripPointerCasts();
-
-    // This two checks are basically similar. First one is here for the
-    // consistency with findBasePointers logic.
-    assert(!isa<CastInst>(Def) && "not a pointer cast found");
-    if (!CI->isNoopCast(CI->getModule()->getDataLayout()))
-      return false;
-
     ChainToBase.push_back(CI);
-    return findRematerializableChainToBasePointer(ChainToBase, Def, BaseValue);
+    return findRematerializableChainToBasePointer(ChainToBase,
+                                                  CI->getOperand(0), BaseValue);
   }
 
   // Not supported instruction in the chain


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