[llvm] r270993 - [RewriteStatepointsForGC] All constant should have null base pointer
Igor Laevsky via llvm-commits
llvm-commits at lists.llvm.org
Fri May 27 06:14:04 PDT 2016
Author: igor.laevsky
Date: Fri May 27 08:13:59 2016
New Revision: 270993
URL: http://llvm.org/viewvc/llvm-project?rev=270993&view=rev
Log:
[RewriteStatepointsForGC] All constant should have null base pointer
Currently we consider that each constant has itself as a base value. I.e "base(const) = const".
This introduces couple of problems when we are trying to avoid reporting constants in statepoint live sets:
1. When querying "base( phi(const1, const2) )" we will get "phi(const1, const2)" as a base pointer. Since
it's not a constant we will record it in a stack map. However on practice we don't want this to happen
(constant are never relocated).
2. base( phi(const, gc ptr) ) = phi( const, base(gc ptr) ). This particular case imposes challenge on our
runtime - we don't expect to see constant base pointers other than null. This problems can be avoided
by treating all constant as if they were derived from null pointer base. I.e in a first case we will
not include constant pointer in a stack map at all. In a second case we will get "phi(null, base(gc ptr))"
as a base pointer which is a lot more convenient.
Differential Revision: http://reviews.llvm.org/D20584
Modified:
llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-pointers-12.ll
llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-pointers-13.ll
llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-vector.ll
llvm/trunk/test/Transforms/RewriteStatepointsForGC/constants.ll
Modified: llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp?rev=270993&r1=270992&r2=270993&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp Fri May 27 08:13:59 2016
@@ -343,8 +343,10 @@ findBaseDefiningValueOfVector(Value *I)
return BaseDefiningValueResult(I, true);
if (isa<Constant>(I))
- // Constant vectors consist only of constant pointers.
- return BaseDefiningValueResult(I, true);
+ // Base of constant vector consists only of constant null pointers.
+ // For reasoning see similar case inside 'findBaseDefiningValue' function.
+ return BaseDefiningValueResult(ConstantAggregateZero::get(I->getType()),
+ true);
if (isa<LoadInst>(I))
return BaseDefiningValueResult(I, true);
@@ -386,14 +388,20 @@ static BaseDefiningValueResult findBaseD
// We should have never reached here if this argument isn't an gc value
return BaseDefiningValueResult(I, true);
- if (isa<Constant>(I))
+ if (isa<Constant>(I)) {
// We assume that objects with a constant base (e.g. a global) can't move
// and don't need to be reported to the collector because they are always
- // live. All constants have constant bases. Besides global references, all
- // kinds of constants (e.g. undef, constant expressions, null pointers) can
- // be introduced by the inliner or the optimizer, especially on dynamically
- // dead paths. See e.g. test4 in constants.ll.
- return BaseDefiningValueResult(I, true);
+ // live. Besides global references, all kinds of constants (e.g. undef,
+ // constant expressions, null pointers) can be introduced by the inliner or
+ // the optimizer, especially on dynamically dead paths.
+ // Here we treat all of them as having single null base. By doing this we
+ // trying to avoid problems reporting various conflicts in a form of
+ // "phi (const1, const2)" or "phi (const, regular gc ptr)".
+ // See constant.ll file for relevant test cases.
+
+ return BaseDefiningValueResult(
+ ConstantPointerNull::get(cast<PointerType>(I->getType())), true);
+ }
if (CastInst *CI = dyn_cast<CastInst>(I)) {
Value *Def = CI->stripPointerCasts();
Modified: llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-pointers-12.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-pointers-12.ll?rev=270993&r1=270992&r2=270993&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-pointers-12.ll (original)
+++ llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-pointers-12.ll Fri May 27 08:13:59 2016
@@ -1,6 +1,6 @@
; RUN: opt < %s -rewrite-statepoints-for-gc -spp-print-base-pointers -S 2>&1 | FileCheck %s
-; CHECK: derived %select base @global
+; CHECK: derived %select base null
@global = external addrspace(1) global i8
Modified: llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-pointers-13.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-pointers-13.ll?rev=270993&r1=270992&r2=270993&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-pointers-13.ll (original)
+++ llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-pointers-13.ll Fri May 27 08:13:59 2016
@@ -1,6 +1,6 @@
; RUN: opt < %s -rewrite-statepoints-for-gc -spp-print-base-pointers -S 2>&1 | FileCheck %s
-; CHECK: derived %derived base @global
+; CHECK: derived %derived base null
@global = external addrspace(1) global i8
Modified: llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-vector.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-vector.ll?rev=270993&r1=270992&r2=270993&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-vector.ll (original)
+++ llvm/trunk/test/Transforms/RewriteStatepointsForGC/base-vector.ll Fri May 27 08:13:59 2016
@@ -106,7 +106,7 @@ entry:
define void @test6(i1 %cnd, i64 addrspace(1)* %obj, i64 %idx) gc "statepoint-example" {
; CHECK-LABEL: @test6
; CHECK: %gep = getelementptr i64, i64 addrspace(1)* %obj, i64 1
-; CHECK: %vec.base = insertelement <2 x i64 addrspace(1)*> undef, i64 addrspace(1)* %obj, i32 0, !is_base_value !0
+; CHECK: %vec.base = insertelement <2 x i64 addrspace(1)*> zeroinitializer, i64 addrspace(1)* %obj, i32 0, !is_base_value !0
; CHECK: %vec = insertelement <2 x i64 addrspace(1)*> undef, i64 addrspace(1)* %gep, i32 0
; CHECK: %bdv.base = extractelement <2 x i64 addrspace(1)*> %vec.base, i64 %idx, !is_base_value !0
; CHECK: %bdv = extractelement <2 x i64 addrspace(1)*> %vec, i64 %idx
Modified: llvm/trunk/test/Transforms/RewriteStatepointsForGC/constants.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/RewriteStatepointsForGC/constants.ll?rev=270993&r1=270992&r2=270993&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/RewriteStatepointsForGC/constants.ll (original)
+++ llvm/trunk/test/Transforms/RewriteStatepointsForGC/constants.ll Fri May 27 08:13:59 2016
@@ -117,3 +117,147 @@ entry:
call void @foo() [ "deopt"() ]
ret i8 addrspace(1)* %load_addr
}
+
+define i8 @test8(i8 addrspace(1)* %p) gc "statepoint-example" {
+; Checks that base( phi(gep null, oop) ) = phi(null, base(oop)) and that we
+; correctly relocate this value
+; CHECK-LABEL: @test8
+entry:
+ %is_null = icmp eq i8 addrspace(1)* %p, null
+ br i1 %is_null, label %null.crit-edge, label %not-null
+
+not-null:
+ %load_addr = getelementptr inbounds i8, i8 addrspace(1)* %p, i64 8
+ br label %join
+
+null.crit-edge:
+ %load_addr.const = getelementptr inbounds i8, i8 addrspace(1)* null, i64 8
+ br label %join
+
+join:
+ %addr = phi i8 addrspace(1)* [ %load_addr, %not-null ], [%load_addr.const, %null.crit-edge]
+ ; CHECK: %addr.base = phi i8 addrspace(1)*
+ ; CHECK-DAG: [ %p, %not-null ]
+ ; CHECK-DAG: [ null, %null.crit-edge ]
+ ; CHECK: gc.statepoint
+ call void @foo() [ "deopt"() ]
+ ; CHECK-DAG: call {{.*}}gc.relocate{{.*}}(%addr.base, %addr.base)
+ ; CHECK-DAG: call {{.*}}gc.relocate{{.*}}(%addr.base, %addr)
+ br i1 %is_null, label %early-exit, label %use
+
+early-exit:
+ ret i8 0
+
+use:
+ %res = load i8, i8 addrspace(1)* %addr, align 1
+ ret i8 %res
+}
+
+define i8 @test9(i8 addrspace(1)* %p) gc "statepoint-example" {
+; Checks that base( phi(inttoptr, oop) ) = phi(null, base(oop)) and that we
+; correctly relocate this value
+; CHECK-LABEL: @test9
+entry:
+ %is_null = icmp eq i8 addrspace(1)* %p, null
+ br i1 %is_null, label %null.crit-edge, label %not-null
+
+not-null:
+ %load_addr = getelementptr inbounds i8, i8 addrspace(1)* %p, i64 8
+ br label %join
+
+null.crit-edge:
+ br label %join
+
+join:
+ %addr = phi i8 addrspace(1)* [ %load_addr, %not-null ], [inttoptr (i64 8 to i8 addrspace(1)*), %null.crit-edge]
+ ; CHECK: %addr.base = phi i8 addrspace(1)*
+ ; CHECK-DAG: [ %p, %not-null ]
+ ; CHECK-DAG: [ null, %null.crit-edge ]
+ ; CHECK: gc.statepoint
+ call void @foo() [ "deopt"() ]
+ ; CHECK-DAG: call {{.*}}gc.relocate{{.*}}(%addr.base, %addr.base)
+ ; CHECK-DAG: call {{.*}}gc.relocate{{.*}}(%addr.base, %addr)
+ br i1 %is_null, label %early-exit, label %use
+
+early-exit:
+ ret i8 0
+
+use:
+ %res = load i8, i8 addrspace(1)* %addr, align 1
+ ret i8 %res
+}
+
+define i8 @test10(i8 addrspace(1)* %p) gc "statepoint-example" {
+; Checks that base( phi(const gep, oop) ) = phi(null, base(oop)) and that we
+; correctly relocate this value
+; CHECK-LABEL: @test10
+entry:
+ %is_null = icmp eq i8 addrspace(1)* %p, null
+ br i1 %is_null, label %null.crit-edge, label %not-null
+
+not-null:
+ %load_addr = getelementptr inbounds i8, i8 addrspace(1)* %p, i64 8
+ br label %join
+
+null.crit-edge:
+ br label %join
+
+join:
+ %addr = phi i8 addrspace(1)* [ %load_addr, %not-null ], [getelementptr (i8, i8 addrspace(1)* null, i64 8), %null.crit-edge]
+ ; CHECK: %addr.base = phi i8 addrspace(1)*
+ ; CHECK-DAG: [ %p, %not-null ]
+ ; CHECK-DAG: [ null, %null.crit-edge ]
+ ; CHECK: gc.statepoint
+ call void @foo() [ "deopt"() ]
+ ; CHECK-DAG: call {{.*}}gc.relocate{{.*}}(%addr.base, %addr.base)
+ ; CHECK-DAG: call {{.*}}gc.relocate{{.*}}(%addr.base, %addr)
+ br i1 %is_null, label %early-exit, label %use
+
+early-exit:
+ ret i8 0
+
+use:
+ %res = load i8, i8 addrspace(1)* %addr, align 1
+ ret i8 %res
+}
+
+define i32 addrspace(1)* @test11(i1 %c) gc "statepoint-example" {
+; CHECK-LABEL: @test11
+; Checks that base( select(const1, const2) ) == null and that we don't record
+; such value in the oop map
+entry:
+ %val = select i1 %c, i32 addrspace(1)* inttoptr (i64 8 to i32 addrspace(1)*), i32 addrspace(1)* inttoptr (i64 15 to i32 addrspace(1)*)
+ ; CHECK: gc.statepoint
+ ; CHECK-NOT: call {{.*}}gc.relocate
+ call void @foo() [ "deopt"() ]
+ ret i32 addrspace(1)* %val
+}
+
+
+define <2 x i32 addrspace(1)*> @test12(i1 %c) gc "statepoint-example" {
+; CHECK-LABEL: @test12
+; Same as test11 but with vectors
+entry:
+ %val = select i1 %c, <2 x i32 addrspace(1)*> <i32 addrspace(1)* inttoptr (i64 5 to i32 addrspace(1)*),
+ i32 addrspace(1)* inttoptr (i64 15 to i32 addrspace(1)*)>,
+ <2 x i32 addrspace(1)*> <i32 addrspace(1)* inttoptr (i64 30 to i32 addrspace(1)*),
+ i32 addrspace(1)* inttoptr (i64 60 to i32 addrspace(1)*)>
+ ; CHECK: gc.statepoint
+ ; CHECK-NOT: call {{.*}}gc.relocate
+ call void @foo() [ "deopt"() ]
+ ret <2 x i32 addrspace(1)*> %val
+}
+
+define <2 x i32 addrspace(1)*> @test13(i1 %c, <2 x i32 addrspace(1)*> %ptr) gc "statepoint-example" {
+; CHECK-LABEL: @test13
+; Similar to test8, test9 and test10 but with vectors
+entry:
+ %val = select i1 %c, <2 x i32 addrspace(1)*> %ptr,
+ <2 x i32 addrspace(1)*> <i32 addrspace(1)* inttoptr (i64 30 to i32 addrspace(1)*), i32 addrspace(1)* inttoptr (i64 60 to i32 addrspace(1)*)>
+ ; CHECK: %val.base = select i1 %c, <2 x i32 addrspace(1)*> %ptr, <2 x i32 addrspace(1)*> zeroinitializer, !is_base_value !0
+ ; CHECK: gc.statepoint
+ call void @foo() [ "deopt"() ]
+ ; CHECK-DAG: call {{.*}}gc.relocate{{.*}}(%val.base, %val.base)
+ ; CHECK-DAG: call {{.*}}gc.relocate{{.*}}(%val.base, %val)
+ ret <2 x i32 addrspace(1)*> %val
+}
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