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llvm-mirror/test/CodeGen/X86/tailcall-assume.ll
Guozhi Wei 2020af31f5 [CodeGen/Analysis] Intrinsic llvm.assume should not block tail call optimization
In function Analysis.cpp:isInTailCallPosition, instructions between call and ret are checked to see if they block tail call optimization. If an instruction is an intrinsic call, only llvm.lifetime_end is allowed and other intrinsic functions block tail call. When compiling tcmalloc, we found llvm.assume between a hot function call and ret, it blocks the optimization. But llvm.assume doesn't generate instructions, it should not block tail call.

Differential Revision: https://reviews.llvm.org/D66096

llvm-svn: 369125
2019-08-16 16:26:12 +00:00

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LLVM

; RUN: llc -mtriple=x86_64-linux < %s | FileCheck %s
; Intrinsic call to @llvm.assume should not prevent tail call optimization.
; CHECK-LABEL: foo:
; CHECK: jmp bar # TAILCALL
define i8* @foo() {
%1 = tail call i8* @bar()
%2 = icmp ne i8* %1, null
tail call void @llvm.assume(i1 %2)
ret i8* %1
}
declare i8* @bar()
declare void @llvm.assume(i1)