WholeProgramDevirt: introduce.
This pass implements whole program optimization of virtual calls in cases
where we know (via bitset information) that the list of callees is fixed. This
includes the following:
- Single implementation devirtualization: if a virtual call has a single
possible callee, replace all calls with a direct call to that callee.
- Virtual constant propagation: if the virtual function's return type is an
integer <=64 bits and all possible callees are readnone, for each class and
each list of constant arguments: evaluate the function, store the return
value alongside the virtual table, and rewrite each virtual call as a load
from the virtual table.
- Uniform return value optimization: if the conditions for virtual constant
propagation hold and each function returns the same constant value, replace
each virtual call with that constant.
- Unique return value optimization for i1 return values: if the conditions
for virtual constant propagation hold and a single vtable's function
returns 0, or a single vtable's function returns 1, replace each virtual
call with a comparison of the vptr against that vtable's address.
Differential Revision: http://reviews.llvm.org/D16795
llvm-svn: 260312
diff --git a/llvm/test/Transforms/WholeProgramDevirt/vcp-accesses-memory.ll b/llvm/test/Transforms/WholeProgramDevirt/vcp-accesses-memory.ll
new file mode 100644
index 0000000..f963d18
--- /dev/null
+++ b/llvm/test/Transforms/WholeProgramDevirt/vcp-accesses-memory.ll
@@ -0,0 +1,37 @@
+; RUN: opt -S -wholeprogramdevirt %s | FileCheck %s
+
+target datalayout = "e-p:64:64"
+target triple = "x86_64-unknown-linux-gnu"
+
+@vt1 = global [1 x i8*] [i8* bitcast (i32 (i8*, i32)* @vf1 to i8*)]
+@vt2 = global [1 x i8*] [i8* bitcast (i32 (i8*, i32)* @vf2 to i8*)]
+
+define i32 @vf1(i8* %this, i32 %arg) {
+ ret i32 %arg
+}
+
+define i32 @vf2(i8* %this, i32 %arg) {
+ ret i32 %arg
+}
+
+; CHECK: define i32 @call
+define i32 @call(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.bitset.test(i8* %vtablei8, metadata !"bitset")
+ call void @llvm.assume(i1 %p)
+ %fptrptr = getelementptr [1 x i8*], [1 x i8*]* %vtable, i32 0, i32 0
+ %fptr = load i8*, i8** %fptrptr
+ %fptr_casted = bitcast i8* %fptr to i32 (i8*, i32)*
+ ; CHECK: call i32 %
+ %result = call i32 %fptr_casted(i8* %obj, i32 1)
+ ret i32 %result
+}
+
+declare i1 @llvm.bitset.test(i8*, metadata)
+declare void @llvm.assume(i1)
+
+!0 = !{!"bitset", [1 x i8*]* @vt1, i32 0}
+!1 = !{!"bitset", [1 x i8*]* @vt2, i32 0}
+!llvm.bitsets = !{!0}