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llvm-project/llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-check.ll
PiJoules 2661e995ce
[llvm] Ensure propagated constants in the vtable are aligned (#136630) 
It's possible for virtual constant propagation in whole program
devirtualization to create unaligned loads. We originally saw this with
4-byte aligned relative vtables where we could store 8-byte values
before/after the vtable. But since the vtable is 4-byte aligned and we
unconditionally do an 8-byte load, we can't guarantee that the stored
constant will always be aligned to 8 bytes. We can also see this with
normal vtables whenever a 1-byte char is stored in the vtable because
the offset calculation for the GEP doesn't take into account the
original vtable alignment.

This patch introduces two changes to virtual constant propagation:
1. Do not propagate constants whose preferred alignment is larger than
the vtable alignment. This is required because if the constants are
stored in the vtable, we can only guarantee the constant will be stored
at an address at most aligned to the vtable's alignment.
2. Round up the offset used in the GEP before the load to ensure it's at
an address suitably aligned such that we can load from it.

This patch updates tests to reflect this alignment change and adds some
cases for relative vtables.
2025-05-15 11:52:25 -07:00

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; -stats requires asserts
; REQUIRES: asserts
; RUN: opt -S -passes=wholeprogramdevirt -whole-program-visibility -pass-remarks=wholeprogramdevirt -stats %s 2>&1 | FileCheck %s
; Skipping vf0i1 is identical to setting public LTO visibility. We don't devirtualize vf0i1 and all other
; virtual call targets.
; RUN: opt -S -passes=wholeprogramdevirt -whole-program-visibility -pass-remarks=wholeprogramdevirt -wholeprogramdevirt-skip=vf0i1 %s 2>&1 | FileCheck %s --check-prefix=SKIP
; We have two set of call targets {vf0i1, vf1i1} and {vf1i32, vf2i32, vf3i32, vf4i32}.
; The command below prevents both of them from devirtualization.
; RUN: opt -S -passes=wholeprogramdevirt -whole-program-visibility -pass-remarks=wholeprogramdevirt -wholeprogramdevirt-skip=vf0i1,vf1i32,vf3i32 %s 2>&1 | FileCheck %s --check-prefix=SKIP-ALL
; Check wildcard
; RUN: opt -S -passes=wholeprogramdevirt -whole-program-visibility -pass-remarks=wholeprogramdevirt -wholeprogramdevirt-skip=vf?i1 %s 2>&1 | FileCheck %s --check-prefix=SKIP
target datalayout = "e-p:64:64"
target triple = "x86_64-unknown-linux-gnu"
; CHECK: remark: <unknown>:0:0: unique-ret-val: devirtualized a call to vf0i1
; CHECK: remark: <unknown>:0:0: unique-ret-val: devirtualized a call to vf1i1
; CHECK: remark: <unknown>:0:0: virtual-const-prop: devirtualized a call to vf3i32
; CHECK: remark: <unknown>:0:0: virtual-const-prop-1-bit: devirtualized a call to vf0i1
; CHECK: remark: <unknown>:0:0: virtual-const-prop-1-bit: devirtualized a call to vf1i1
; CHECK: remark: <unknown>:0:0: virtual-const-prop: devirtualized a call to vf1i32
; CHECK: remark: <unknown>:0:0: devirtualized vf0i1
; CHECK: remark: <unknown>:0:0: devirtualized vf1i1
; CHECK: remark: <unknown>:0:0: devirtualized vf1i32
; CHECK: remark: <unknown>:0:0: devirtualized vf2i32
; CHECK: remark: <unknown>:0:0: devirtualized vf3i32
; CHECK: remark: <unknown>:0:0: devirtualized vf4i32
; CHECK-NOT: devirtualized
; SKIP: remark: <unknown>:0:0: virtual-const-prop: devirtualized a call to vf1i32
; SKIP: remark: <unknown>:0:0: devirtualized vf1i32
; SKIP: remark: <unknown>:0:0: devirtualized vf2i32
; SKIP: remark: <unknown>:0:0: devirtualized vf3i32
; SKIP: remark: <unknown>:0:0: devirtualized vf4i32
; SKIP-NOT: devirtualized
; SKIP-ALL-NOT: devirtualized
; CHECK: [[VT1DATA:@[^ ]*]] = private constant { [8 x i8], [3 x ptr], [4 x i8] } { [8 x i8] c"\00\00\00\00\00\00\00\02", [3 x ptr] [ptr @vf0i1, ptr @vf1i1, ptr @vf1i32], [4 x i8] c"\01\00\00\00" }, section "vt1sec", !type [[T8:![0-9]+]]
@vt1 = constant [3 x ptr] [
ptr @vf0i1,
ptr @vf1i1,
ptr @vf1i32
], section "vt1sec", !type !0
; CHECK: [[VT2DATA:@[^ ]*]] = private constant { [8 x i8], [3 x ptr], [4 x i8] } { [8 x i8] c"\00\00\00\00\00\00\00\01", [3 x ptr] [ptr @vf1i1, ptr @vf0i1, ptr @vf2i32], [4 x i8] c"\02\00\00\00" }, !type [[T8]]
@vt2 = constant [3 x ptr] [
ptr @vf1i1,
ptr @vf0i1,
ptr @vf2i32
], !type !0
; CHECK: [[VT3DATA:@[^ ]*]] = private constant { [8 x i8], [3 x ptr], [4 x i8] } { [8 x i8] c"\00\00\00\00\00\00\00\02", [3 x ptr] [ptr @vf0i1, ptr @vf1i1, ptr @vf3i32], [4 x i8] c"\03\00\00\00" }, !type [[T8]]
@vt3 = constant [3 x ptr] [
ptr @vf0i1,
ptr @vf1i1,
ptr @vf3i32
], !type !0
; CHECK: [[VT4DATA:@[^ ]*]] = private constant { [8 x i8], [3 x ptr], [4 x i8] } { [8 x i8] c"\00\00\00\00\00\00\00\01", [3 x ptr] [ptr @vf1i1, ptr @vf0i1, ptr @vf4i32], [4 x i8] c"\04\00\00\00" }, !type [[T8]]
@vt4 = constant [3 x ptr] [
ptr @vf1i1,
ptr @vf0i1,
ptr @vf4i32
], !type !0
; CHECK: @vt5 = {{.*}}, !type [[T0:![0-9]+]]
@vt5 = constant [3 x ptr] [
ptr @__cxa_pure_virtual,
ptr @__cxa_pure_virtual,
ptr @__cxa_pure_virtual
], !type !0
;; Test relative vtables
; CHECK: [[VT6RELDATA:@[^ ]*]] = private constant { [4 x i8], [3 x i32], [0 x i8] } { [4 x i8] c"\03\00\00\00", [3 x i32] [
; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vf0i1 to i64), i64 ptrtoint (ptr @vt6_rel to i64)) to i32),
; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vf1i1 to i64), i64 ptrtoint (ptr @vt6_rel to i64)) to i32),
; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vf3i32 to i64), i64 ptrtoint (ptr @vt6_rel to i64)) to i32)
; CHECK-SAME: ], [0 x i8] zeroinitializer }, !type [[TREL:![0-9]+]]
@vt6_rel = constant [3 x i32] [
i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vf0i1 to i64), i64 ptrtoint (ptr @vt6_rel to i64)) to i32),
i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vf1i1 to i64), i64 ptrtoint (ptr @vt6_rel to i64)) to i32),
i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vf3i32 to i64), i64 ptrtoint (ptr @vt6_rel to i64)) to i32)
], !type !1
; CHECK: [[VT7RELDATA:@[^ ]*]] = private constant { [4 x i8], [3 x i32], [0 x i8] } { [4 x i8] c"\04\00\00\00", [3 x i32] [
; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vf1i1 to i64), i64 ptrtoint (ptr @vt7_rel to i64)) to i32),
; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vf0i1 to i64), i64 ptrtoint (ptr @vt7_rel to i64)) to i32),
; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vf4i32 to i64), i64 ptrtoint (ptr @vt7_rel to i64)) to i32)
; CHECK-SAME: ], [0 x i8] zeroinitializer }, !type [[TREL]]
@vt7_rel = constant [3 x i32] [
i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vf1i1 to i64), i64 ptrtoint (ptr @vt7_rel to i64)) to i32),
i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vf0i1 to i64), i64 ptrtoint (ptr @vt7_rel to i64)) to i32),
i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @vf4i32 to i64), i64 ptrtoint (ptr @vt7_rel to i64)) to i32)
], !type !1
; CHECK: @vt1 = alias [3 x ptr], getelementptr inbounds ({ [8 x i8], [3 x ptr], [4 x i8] }, ptr [[VT1DATA]], i32 0, i32 1)
; CHECK: @vt2 = alias [3 x ptr], getelementptr inbounds ({ [8 x i8], [3 x ptr], [4 x i8] }, ptr [[VT2DATA]], i32 0, i32 1)
; CHECK: @vt3 = alias [3 x ptr], getelementptr inbounds ({ [8 x i8], [3 x ptr], [4 x i8] }, ptr [[VT3DATA]], i32 0, i32 1)
; CHECK: @vt4 = alias [3 x ptr], getelementptr inbounds ({ [8 x i8], [3 x ptr], [4 x i8] }, ptr [[VT4DATA]], i32 0, i32 1)
; CHECK: @vt6_rel = alias [3 x i32], getelementptr inbounds ({ [4 x i8], [3 x i32], [0 x i8] }, ptr [[VT6RELDATA]], i32 0, i32 1)
; CHECK: @vt7_rel = alias [3 x i32], getelementptr inbounds ({ [4 x i8], [3 x i32], [0 x i8] }, ptr [[VT7RELDATA]], i32 0, i32 1)
define i1 @vf0i1(ptr %this) readnone {
ret i1 0
}
define i1 @vf1i1(ptr %this) readnone {
ret i1 1
}
define i32 @vf1i32(ptr %this) readnone {
ret i32 1
}
define i32 @vf2i32(ptr %this) readnone {
ret i32 2
}
define i32 @vf3i32(ptr %this) readnone {
ret i32 3
}
define i32 @vf4i32(ptr %this) readnone {
ret i32 4
}
; CHECK: define i1 @call1(
define i1 @call1(ptr %obj) {
%vtable = load ptr, ptr %obj
%pair = call {ptr, i1} @llvm.type.checked.load(ptr %vtable, i32 0, metadata !"typeid")
%fptr = extractvalue {ptr, i1} %pair, 0
; CHECK: [[VTGEP1:%[^ ]*]] = getelementptr i8, ptr %vtable, i32 -1
; CHECK: [[VTLOAD1:%[^ ]*]] = load i8, ptr [[VTGEP1]]
; CHECK: [[VTAND1:%[^ ]*]] = and i8 [[VTLOAD1]], 1
; CHECK: [[VTCMP1:%[^ ]*]] = icmp ne i8 [[VTAND1]], 0
%result = call i1 %fptr(ptr %obj)
; CHECK: [[AND1:%[^ ]*]] = and i1 [[VTCMP1]], true
%p = extractvalue {ptr, i1} %pair, 1
%and = and i1 %result, %p
; CHECK: ret i1 [[AND1]]
ret i1 %and
}
; CHECK: define i1 @call2(
define i1 @call2(ptr %obj) {
%vtable = load ptr, ptr %obj
%pair = call {ptr, i1} @llvm.type.checked.load(ptr %vtable, i32 8, metadata !"typeid")
%fptr = extractvalue {ptr, i1} %pair, 0
; CHECK: [[VTGEP2:%[^ ]*]] = getelementptr i8, ptr %vtable, i32 -1
; CHECK: [[VTLOAD2:%[^ ]*]] = load i8, ptr [[VTGEP2]]
; CHECK: [[VTAND2:%[^ ]*]] = and i8 [[VTLOAD2]], 2
; CHECK: [[VTCMP2:%[^ ]*]] = icmp ne i8 [[VTAND2]], 0
%result = call i1 %fptr(ptr %obj)
; CHECK: [[AND2:%[^ ]*]] = and i1 [[VTCMP2]], true
%p = extractvalue {ptr, i1} %pair, 1
%and = and i1 %result, %p
; CHECK: ret i1 [[AND2]]
ret i1 %and
}
; CHECK: define i32 @call3(
define i32 @call3(ptr %obj) {
%vtable = load ptr, ptr %obj
%pair = call {ptr, i1} @llvm.type.checked.load(ptr %vtable, i32 16, metadata !"typeid")
%fptr = extractvalue {ptr, i1} %pair, 0
; CHECK: [[VTGEP3:%[^ ]*]] = getelementptr i8, ptr %vtable, i32 24
; CHECK: [[VTLOAD3:%[^ ]*]] = load i32, ptr [[VTGEP3]]
%result = call i32 %fptr(ptr %obj)
; CHECK: ret i32 [[VTLOAD3]]
ret i32 %result
}
; CHECK: define i1 @call1_rel(
define i1 @call1_rel(ptr %obj) {
%vtable = load ptr, ptr %obj
%p = call i1 @llvm.type.test(ptr %vtable, metadata !"typeid2")
call void @llvm.assume(i1 %p)
%fptr = call ptr @llvm.load.relative.i32(ptr %vtable, i32 0)
%result = call i1 %fptr(ptr %obj)
ret i1 %result
; CHECK: [[RES:%[^ ]*]] = icmp eq ptr %vtable, @vt7_rel
; CHECK: ret i1 [[RES]]
}
; CHECK: define i1 @call2_rel(
define i1 @call2_rel(ptr %obj) {
%vtable = load ptr, ptr %obj
%p = call i1 @llvm.type.test(ptr %vtable, metadata !"typeid2")
call void @llvm.assume(i1 %p)
%fptr = call ptr @llvm.load.relative.i32(ptr %vtable, i32 4)
%result = call i1 %fptr(ptr %obj)
ret i1 %result
; CHECK: [[RES:%[^ ]*]] = icmp eq ptr %vtable, @vt6_rel
; CHECK: ret i1 [[RES]]
}
; CHECK: define i32 @call3_rel(
define i32 @call3_rel(ptr %obj) {
%vtable = load ptr, ptr %obj
%p = call i1 @llvm.type.test(ptr %vtable, metadata !"typeid2")
call void @llvm.assume(i1 %p)
%fptr = call ptr @llvm.load.relative.i32(ptr %vtable, i32 8)
; CHECK: [[VTGEP3:%[^ ]*]] = getelementptr i8, ptr %vtable, i32 -4
; CHECK: [[VTLOAD3:%[^ ]*]] = load i32, ptr [[VTGEP3]]
%result = call i32 %fptr(ptr %obj)
; CHECK: ret i32 [[VTLOAD3]]
ret i32 %result
}
declare {ptr, i1} @llvm.type.checked.load(ptr, i32, metadata)
declare void @llvm.assume(i1)
declare void @__cxa_pure_virtual()
declare ptr @llvm.load.relative.i32(ptr, i32)
; CHECK: [[T8]] = !{i32 8, !"typeid"}
; CHECK: [[T0]] = !{i32 0, !"typeid"}
; CHECK: [[TREL]] = !{i32 4, !"typeid2"}
!0 = !{i32 0, !"typeid"}
!1 = !{i32 0, !"typeid2"}
; CHECK: 6 wholeprogramdevirt - Number of whole program devirtualization targets
; CHECK: 2 wholeprogramdevirt - Number of unique return value optimizations
; CHECK: 2 wholeprogramdevirt - Number of virtual constant propagations
; CHECK: 2 wholeprogramdevirt - Number of 1 bit virtual constant propagations
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