WholeProgramDevirt: Examine the function body when deciding whether functions are readnone.

The goal is to get an analysis result even for de-refineable functions.

Differential Revision: https://reviews.llvm.org/D29803

llvm-svn: 295472

1 files changed, 40 insertions, 6 deletions

diff --git a/llvm/test/Transforms/WholeProgramDevirt/vcp-accesses-memory.ll b/llvm/test/Transforms/WholeProgramDevirt/vcp-accesses-memory.ll
index c4aad658100..ca76383c494 100644
--- a/llvm/test/Transforms/WholeProgramDevirt/vcp-accesses-memory.ll
+++ b/llvm/test/Transforms/WholeProgramDevirt/vcp-accesses-memory.ll
@@ -1,21 +1,37 @@
 ; RUN: opt -S -wholeprogramdevirt %s | FileCheck %s
+; RUN: opt -S -passes=wholeprogramdevirt %s | FileCheck %s
 
 target datalayout = "e-p:64:64"
 target triple = "x86_64-unknown-linux-gnu"
 
-@vt1 = constant [1 x i8*] [i8* bitcast (i32 (i8*, i32)* @vf1 to i8*)], !type !0
-@vt2 = constant [1 x i8*] [i8* bitcast (i32 (i8*, i32)* @vf2 to i8*)], !type !0
+@vt1 = constant [2 x i8*] [i8* bitcast (i32 (i8*, i32)* @vf1a to i8*), i8* bitcast (i32 (i8*, i32)* @vf1b to i8*)], !type !0
+@vt2 = constant [2 x i8*] [i8* bitcast (i32 (i8*, i32)* @vf2a to i8*), i8* bitcast (i32 (i8*, i32)* @vf2b to i8*)], !type !0
 
-define i32 @vf1(i8* %this, i32 %arg) {
+@sink = external global i32
+
+define i32 @vf1a(i8* %this, i32 %arg) {
+  store i32 %arg, i32* @sink
+  ret i32 %arg
+}
+
+define i32 @vf2a(i8* %this, i32 %arg) {
+  store i32 %arg, i32* @sink
+  ret i32 %arg
+}
+
+define i32 @vf1b(i8* %this, i32 %arg) {
   ret i32 %arg
 }
 
-define i32 @vf2(i8* %this, i32 %arg) {
+define i32 @vf2b(i8* %this, i32 %arg) {
   ret i32 %arg
 }
 
-; CHECK: define i32 @call
-define i32 @call(i8* %obj) {
+; Test that we don't apply VCP if the virtual function body accesses memory,
+; even if the function returns a constant.
+
+; CHECK: define i32 @call1
+define i32 @call1(i8* %obj) {
   %vtableptr = bitcast i8* %obj to [1 x i8*]**
   %vtable = load [1 x i8*]*, [1 x i8*]** %vtableptr
   %vtablei8 = bitcast [1 x i8*]* %vtable to i8*
@@ -29,6 +45,24 @@ define i32 @call(i8* %obj) {
   ret i32 %result
 }
 
+; Test that we can apply VCP regardless of the function attributes by analyzing
+; the function body itself.
+
+; CHECK: define i32 @call2
+define i32 @call2(i8* %obj) {
+  %vtableptr = bitcast i8* %obj to [1 x i8*]**
+  %vtable = load [1 x i8*]*, [1 x i8*]** %vtableptr
+  %vtablei8 = bitcast [1 x i8*]* %vtable to i8*
+  %p = call i1 @llvm.type.test(i8* %vtablei8, metadata !"typeid")
+  call void @llvm.assume(i1 %p)
+  %fptrptr = getelementptr [1 x i8*], [1 x i8*]* %vtable, i32 0, i32 1
+  %fptr = load i8*, i8** %fptrptr
+  %fptr_casted = bitcast i8* %fptr to i32 (i8*, i32)*
+  %result = call i32 %fptr_casted(i8* %obj, i32 1)
+  ; CHECK: ret i32 1
+  ret i32 %result
+}
+
 declare i1 @llvm.type.test(i8*, metadata)
 declare void @llvm.assume(i1)