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[RS4GC] Look through vector bitcasts when looking for base pointer

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Summary:
 In RS4GC it is possible that a base pointer is contained in a vector that
has undergone a bitcast from one element-pointertype to another. We teach
RS4GC how to look through bitcasts of vector types when looking for a base
pointer.

Reviewers: anna

Reviewed By: anna

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D38849

llvm-svn: 315694
This commit is contained in:
Daniel Neilson 2017-10-13 15:59:13 +00:00
parent 30d967dfc0
commit 2ff4466d0b
2 changed files with 31 additions and 0 deletions
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5
lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
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@ -421,6 +421,11 @@ findBaseDefiningValueOfVector(Value *I) {
if (auto *GEP = dyn_cast<GetElementPtrInst>(I))
return findBaseDefiningValue(GEP->getPointerOperand());
// If the pointer comes through a bitcast of a vector of pointers to
// a vector of another type of pointer, then look through the bitcast
if (auto *BC = dyn_cast<BitCastInst>(I))
return findBaseDefiningValue(BC->getOperand(0));
// A PHI or Select is a base defining value. The outer findBasePointer
// algorithm is responsible for constructing a base value for this BDV.
assert((isa<SelectInst>(I) || isa<PHINode>(I)) &&

26
test/Transforms/RewriteStatepointsForGC/vector-bitcast.ll Normal file
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@ -0,0 +1,26 @@
; RUN: opt -S -rewrite-statepoints-for-gc < %s | FileCheck %s
;
; A test to make sure that we can look through bitcasts of
; vector types when a base pointer is contained in a vector.
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128-ni:1"
target triple = "x86_64-unknown-linux-gnu"
; Function Attrs: uwtable
define void @test() gc "statepoint-example" {
; CHECK-LABEL: @test
entry:
; CHECK-LABEL: entry
; CHECK: %bc = bitcast
; CHECK: %[[p1:[A-Za-z0-9_]+]] = extractelement
; CHECK: %[[p2:[A-Za-z0-9_]+]] = extractelement
; CHECK: llvm.experimental.gc.statepoint
; CHECK: %[[p2]].relocated = {{.+}} @llvm.experimental.gc.relocate
; CHECK: %[[p1]].relocated = {{.+}} @llvm.experimental.gc.relocate
; CHECK: load atomic
%bc = bitcast <8 x i8 addrspace(1)*> undef to <8 x i32 addrspace(1)*>
%ptr= extractelement <8 x i32 addrspace(1)*> %bc, i32 7
%0 = call i8 addrspace(1)* undef() [ "deopt"() ]
%1 = load atomic i32, i32 addrspace(1)* %ptr unordered, align 4
unreachable
}