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llvm-mirror/test/Transforms/InstCombine/vararg.ll
zoecarver 03bc2a070d Re-commit: Mark values as trivially dead when their only use is a start or end lifetime intrinsic.
Summary:
If the only use of a value is a start or end lifetime intrinsic then mark the intrinsic as trivially dead. This should allow for that value to then be removed as well.

Currently, this only works for allocas, globals, and arguments.

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D79355
2020-05-08 12:24:10 -07:00

31 lines
1.0 KiB
LLVM

; RUN: opt < %s -instcombine -instcombine-infinite-loop-threshold=3 -S | FileCheck %s
%struct.__va_list = type { i8*, i8*, i8*, i32, i32 }
declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)
declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture)
declare void @llvm.va_start(i8*)
declare void @llvm.va_end(i8*)
declare void @llvm.va_copy(i8*, i8*)
define i32 @func(i8* nocapture readnone %fmt, ...) {
; CHECK-LABEL: @func(
; CHECK: entry:
; CHECK-NEXT: ret i32 0
entry:
%va0 = alloca %struct.__va_list, align 8
%va1 = alloca %struct.__va_list, align 8
%0 = bitcast %struct.__va_list* %va0 to i8*
%1 = bitcast %struct.__va_list* %va1 to i8*
call void @llvm.lifetime.start.p0i8(i64 32, i8* %0)
call void @llvm.va_start(i8* %0)
call void @llvm.lifetime.start.p0i8(i64 32, i8* %1)
call void @llvm.va_copy(i8* %1, i8* %0)
call void @llvm.va_end(i8* %1)
call void @llvm.lifetime.end.p0i8(i64 32, i8* %1)
call void @llvm.va_end(i8* %0)
call void @llvm.lifetime.end.p0i8(i64 32, i8* %0)
ret i32 0
}