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[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.

llvm-svn: 372771
This commit is contained in:
Philip Reames 2019-09-24 17:24:16 +00:00
parent a7f27f357d
commit d9629b88ff
2 changed files with 23 additions and 1 deletions
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13
llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
View File

@ -3951,10 +3951,21 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
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.

11
llvm/test/Transforms/InstCombine/gc.relocate.ll
View File

@ -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, ...)