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llvm-mirror/test/Transforms/EarlyCSE/read-reg.ll
Hal Finkel 91d2f2d062 Preserve the order of READ_REGISTER and WRITE_REGISTER
At the present time, we don't have a way to represent general dependency
relationships, so everything is represented using memory dependency. In order
to preserve the data dependency of a READ_REGISTER on WRITE_REGISTER, we need
to model WRITE_REGISTER as writing (which we had been doing) and model
READ_REGISTER as reading (which we had not been doing). Fix this, and also the
way that the chain operands were generated at the SDAG level.

Patch by Nicholas Paul Johnson, thanks! Test case by me.

llvm-svn: 237584
2015-05-18 16:42:10 +00:00

35 lines
842 B
LLVM

; RUN: opt -S -early-cse < %s | FileCheck %s
target datalayout = "E-m:e-i64:64-n32:64"
target triple = "powerpc64-unknown-linux-gnu"
; Function Attrs: nounwind
define i64 @f(i64 %x) #0 {
entry:
%0 = call i64 @llvm.read_register.i64(metadata !0)
call void bitcast (void (...)* @foo to void ()*)()
%1 = call i64 @llvm.read_register.i64(metadata !0)
%add = add nsw i64 %0, %1
ret i64 %add
}
; CHECK-LABEL: @f
; CHECK: call i64 @llvm.read_register.i64
; CHECK: call i64 @llvm.read_register.i64
; Function Attrs: nounwind readnone
declare i64 @llvm.read_register.i64(metadata) #1
; Function Attrs: nounwind
declare void @llvm.write_register.i64(metadata, i64) #2
declare void @foo(...)
attributes #0 = { nounwind }
attributes #1 = { nounwind readnone }
attributes #2 = { nounwind }
!llvm.named.register.r1 = !{!0}
!0 = !{!"r1"}