WholeProgramDevirt: Teach the pass to respect the global's alignment.

The bytes inserted before an overaligned global need to be padded according
to the alignment set on the original global in order for the initializer
to meet the global's alignment requirements. The previous implementation
that padded to the pointer width happened to be correct for vtables on most
platforms but may do the wrong thing if the vtable has a larger alignment.

This issue is visible with a prototype implementation of HWASAN for globals,
which will overalign all globals including vtables to 16 bytes.

There is also no padding requirement for the bytes inserted after the global
because they are never read from nor are they significant for alignment
purposes, so stop inserting padding there.

Differential Revision: https://reviews.llvm.org/D65031

llvm-svn: 366725

2 files changed, 16 insertions, 14 deletions

diff --git a/llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-begin.ll b/llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-begin.ll
index 63549e8540c..6e55235ebfc 100644
--- a/llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-begin.ll
+++ b/llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-begin.ll
@@ -17,19 +17,19 @@ i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
 i8* bitcast (i32 (i8*)* @vf2i32 to i8*)
 ], !type !0
 
-; CHECK: [[VT3DATA:@[^ ]*]] = private constant { [8 x i8], [3 x i8*], [0 x i8] } { [8 x i8] c"\00\00\00\01\03\00\00\00", [3 x i8*] [i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf3i32 to i8*)], [0 x i8] zeroinitializer }, !type [[T8]]
+; CHECK: [[VT3DATA:@[^ ]*]] = private constant { [5 x i8], [3 x i8*], [0 x i8] } { [5 x i8] c"\01\03\00\00\00", [3 x i8*] [i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf3i32 to i8*)], [0 x i8] zeroinitializer }, align 1, !type [[T5:![0-9]+]]
 @vt3 = constant [3 x i8*] [
 i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
 i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
 i8* bitcast (i32 (i8*)* @vf3i32 to i8*)
-], !type !0
+], align 1, !type !0
 
-; CHECK: [[VT4DATA:@[^ ]*]] = private constant { [8 x i8], [3 x i8*], [0 x i8] } { [8 x i8] c"\00\00\00\02\04\00\00\00", [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf4i32 to i8*)], [0 x i8] zeroinitializer }, !type [[T8]]
+; CHECK: [[VT4DATA:@[^ ]*]] = private constant { [16 x i8], [3 x i8*], [0 x i8] } { [16 x i8] c"\00\00\00\00\00\00\00\00\00\00\00\02\04\00\00\00", [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf4i32 to i8*)], [0 x i8] zeroinitializer },  align 16, !type [[T16:![0-9]+]]
 @vt4 = constant [3 x i8*] [
 i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
 i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
 i8* bitcast (i32 (i8*)* @vf4i32 to i8*)
-], !type !0
+], align 16, !type !0
 
 ; CHECK: @vt5 = {{.*}}, !type [[T0:![0-9]+]]
 @vt5 = constant [3 x i8*] [
@@ -40,8 +40,8 @@ i8* bitcast (void ()* @__cxa_pure_virtual to i8*)
 
 ; CHECK: @vt1 = alias [3 x i8*], getelementptr inbounds ({ [8 x i8], [3 x i8*], [0 x i8] }, { [8 x i8], [3 x i8*], [0 x i8] }* [[VT1DATA]], i32 0, i32 1)
 ; CHECK: @vt2 = alias [3 x i8*], getelementptr inbounds ({ [8 x i8], [3 x i8*], [0 x i8] }, { [8 x i8], [3 x i8*], [0 x i8] }* [[VT2DATA]], i32 0, i32 1)
-; CHECK: @vt3 = alias [3 x i8*], getelementptr inbounds ({ [8 x i8], [3 x i8*], [0 x i8] }, { [8 x i8], [3 x i8*], [0 x i8] }* [[VT3DATA]], i32 0, i32 1)
-; CHECK: @vt4 = alias [3 x i8*], getelementptr inbounds ({ [8 x i8], [3 x i8*], [0 x i8] }, { [8 x i8], [3 x i8*], [0 x i8] }* [[VT4DATA]], i32 0, i32 1)
+; CHECK: @vt3 = alias [3 x i8*], getelementptr inbounds ({ [5 x i8], [3 x i8*], [0 x i8] }, { [5 x i8], [3 x i8*], [0 x i8] }* [[VT3DATA]], i32 0, i32 1)
+; CHECK: @vt4 = alias [3 x i8*], getelementptr inbounds ({ [16 x i8], [3 x i8*], [0 x i8] }, { [16 x i8], [3 x i8*], [0 x i8] }* [[VT4DATA]], i32 0, i32 1)
 
 define i1 @vf0i1(i8* %this) readnone {
   ret i1 0
@@ -134,6 +134,8 @@ declare void @llvm.assume(i1)
 declare void @__cxa_pure_virtual()
 
 ; CHECK: [[T8]] = !{i32 8, !"typeid"}
+; CHECK: [[T5]] = !{i32 5, !"typeid"}
+; CHECK: [[T16]] = !{i32 16, !"typeid"}
 ; CHECK: [[T0]] = !{i32 0, !"typeid"}
 
 !0 = !{i32 0, !"typeid"}
diff --git a/llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-end.ll b/llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-end.ll
index 3d61e1e2082..5ab9571a0ca 100644
--- a/llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-end.ll
+++ b/llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-end.ll
@@ -3,7 +3,7 @@
 target datalayout = "e-p:64:64"
 target triple = "x86_64-unknown-linux-gnu"
 
-; CHECK: [[VT1DATA:@[^ ]*]] = private constant { [0 x i8], [4 x i8*], [8 x i8] } { [0 x i8] zeroinitializer, [4 x i8*] [i8* null, i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf1i32 to i8*)], [8 x i8] c"\01\00\00\00\01\00\00\00" }, !type [[T8:![0-9]+]]
+; CHECK: [[VT1DATA:@[^ ]*]] = private constant { [0 x i8], [4 x i8*], [5 x i8] } { [0 x i8] zeroinitializer, [4 x i8*] [i8* null, i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf1i32 to i8*)], [5 x i8] c"\01\00\00\00\01" }, !type [[T8:![0-9]+]]
 @vt1 = constant [4 x i8*] [
 i8* null,
 i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
@@ -11,14 +11,14 @@ i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
 i8* bitcast (i32 (i8*)* @vf1i32 to i8*)
 ], !type !1
 
-; CHECK: [[VT2DATA:@[^ ]*]] = private constant { [0 x i8], [3 x i8*], [8 x i8] } { [0 x i8] zeroinitializer, [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf2i32 to i8*)], [8 x i8] c"\02\00\00\00\02\00\00\00" }, !type [[T0:![0-9]+]]
+; CHECK: [[VT2DATA:@[^ ]*]] = private constant { [0 x i8], [3 x i8*], [5 x i8] } { [0 x i8] zeroinitializer, [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf2i32 to i8*)], [5 x i8] c"\02\00\00\00\02" }, !type [[T0:![0-9]+]]
 @vt2 = constant [3 x i8*] [
 i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
 i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
 i8* bitcast (i32 (i8*)* @vf2i32 to i8*)
 ], !type !0
 
-; CHECK: [[VT3DATA:@[^ ]*]] = private constant { [0 x i8], [4 x i8*], [8 x i8] } { [0 x i8] zeroinitializer, [4 x i8*] [i8* null, i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf3i32 to i8*)], [8 x i8] c"\03\00\00\00\01\00\00\00" }, !type [[T8]]
+; CHECK: [[VT3DATA:@[^ ]*]] = private constant { [0 x i8], [4 x i8*], [5 x i8] } { [0 x i8] zeroinitializer, [4 x i8*] [i8* null, i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf3i32 to i8*)], [5 x i8] c"\03\00\00\00\01" }, !type [[T8]]
 @vt3 = constant [4 x i8*] [
 i8* null,
 i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
@@ -26,17 +26,17 @@ i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
 i8* bitcast (i32 (i8*)* @vf3i32 to i8*)
 ], !type !1
 
-; CHECK: [[VT4DATA:@[^ ]*]] = private constant { [0 x i8], [3 x i8*], [8 x i8] } { [0 x i8] zeroinitializer, [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf4i32 to i8*)], [8 x i8] c"\04\00\00\00\02\00\00\00" }, !type [[T0]]
+; CHECK: [[VT4DATA:@[^ ]*]] = private constant { [0 x i8], [3 x i8*], [5 x i8] } { [0 x i8] zeroinitializer, [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf4i32 to i8*)], [5 x i8] c"\04\00\00\00\02" }, !type [[T0]]
 @vt4 = constant [3 x i8*] [
 i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
 i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
 i8* bitcast (i32 (i8*)* @vf4i32 to i8*)
 ], !type !0
 
-; CHECK: @vt1 = alias [4 x i8*], getelementptr inbounds ({ [0 x i8], [4 x i8*], [8 x i8] }, { [0 x i8], [4 x i8*], [8 x i8] }* [[VT1DATA]], i32 0, i32 1)
-; CHECK: @vt2 = alias [3 x i8*], getelementptr inbounds ({ [0 x i8], [3 x i8*], [8 x i8] }, { [0 x i8], [3 x i8*], [8 x i8] }* [[VT2DATA]], i32 0, i32 1)
-; CHECK: @vt3 = alias [4 x i8*], getelementptr inbounds ({ [0 x i8], [4 x i8*], [8 x i8] }, { [0 x i8], [4 x i8*], [8 x i8] }* [[VT3DATA]], i32 0, i32 1)
-; CHECK: @vt4 = alias [3 x i8*], getelementptr inbounds ({ [0 x i8], [3 x i8*], [8 x i8] }, { [0 x i8], [3 x i8*], [8 x i8] }* [[VT4DATA]], i32 0, i32 1)
+; CHECK: @vt1 = alias [4 x i8*], getelementptr inbounds ({ [0 x i8], [4 x i8*], [5 x i8] }, { [0 x i8], [4 x i8*], [5 x i8] }* [[VT1DATA]], i32 0, i32 1)
+; CHECK: @vt2 = alias [3 x i8*], getelementptr inbounds ({ [0 x i8], [3 x i8*], [5 x i8] }, { [0 x i8], [3 x i8*], [5 x i8] }* [[VT2DATA]], i32 0, i32 1)
+; CHECK: @vt3 = alias [4 x i8*], getelementptr inbounds ({ [0 x i8], [4 x i8*], [5 x i8] }, { [0 x i8], [4 x i8*], [5 x i8] }* [[VT3DATA]], i32 0, i32 1)
+; CHECK: @vt4 = alias [3 x i8*], getelementptr inbounds ({ [0 x i8], [3 x i8*], [5 x i8] }, { [0 x i8], [3 x i8*], [5 x i8] }* [[VT4DATA]], i32 0, i32 1)
 
 define i1 @vf0i1(i8* %this) readnone {
   ret i1 0