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Fix PR5247, "lock addq" pattern (and other atomics), it DOES modify EFLAGS.

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LLC was scheduling compares before the adds causing wrong branches to be taken
in programs, resulting in misoptimized code wherever atomic adds where used.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84485 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Torok Edwin 2009-10-19 11:00:58 +00:00
parent e9869d8eeb
commit 6602922878
2 changed files with 71 additions and 1 deletions
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3
lib/Target/X86/X86Instr64bit.td
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@ -1515,6 +1515,7 @@ def XCHG64rm : RI<0x87, MRMSrcMem, (outs GR64:$dst), (ins i64mem:$ptr,GR64:$val)
}
// Optimized codegen when the non-memory output is not used.
let Defs = [EFLAGS] in {
// FIXME: Use normal add / sub instructions and add lock prefix dynamically.
def LOCK_ADD64mr : RI<0x03, MRMDestMem, (outs), (ins i64mem:$dst, GR64:$src2),
"lock\n\t"
@ -1544,7 +1545,7 @@ def LOCK_INC64m : RI<0xFF, MRM0m, (outs), (ins i64mem:$dst),
def LOCK_DEC64m : RI<0xFF, MRM1m, (outs), (ins i64mem:$dst),
"lock\n\t"
"dec{q}\t$dst", []>, LOCK;
}
// Atomic exchange, and, or, xor
let Constraints = "$val = $dst", Defs = [EFLAGS],
usesCustomDAGSchedInserter = 1 in {

69
test/CodeGen/X86/2009-10-19-atomic-cmp-eflags.ll Normal file
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@ -0,0 +1,69 @@
; RUN: llvm-as <%s | llc | FileCheck %s
; PR 5247
; check that cmp is not scheduled before the add
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
target triple = "x86_64-unknown-linux-gnu"
@.str76843 = external constant [45 x i8] ; <[45 x i8]*> [#uses=1]
@__profiling_callsite_timestamps_live = external global [1216 x i64] ; <[1216 x i64]*> [#uses=2]
define i32 @cl_init(i32 %initoptions) nounwind {
entry:
%retval.i = alloca i32 ; <i32*> [#uses=3]
%retval = alloca i32 ; <i32*> [#uses=2]
%initoptions.addr = alloca i32 ; <i32*> [#uses=2]
tail call void asm sideeffect "cpuid", "~{ax},~{bx},~{cx},~{dx},~{memory},~{dirflag},~{fpsr},~{flags}"() nounwind
%0 = tail call i64 @llvm.readcyclecounter() nounwind ; <i64> [#uses=1]
store i32 %initoptions, i32* %initoptions.addr
%1 = bitcast i32* %initoptions.addr to { }* ; <{ }*> [#uses=0]
call void asm sideeffect "cpuid", "~{ax},~{bx},~{cx},~{dx},~{memory},~{dirflag},~{fpsr},~{flags}"() nounwind
%2 = call i64 @llvm.readcyclecounter() nounwind ; <i64> [#uses=1]
%call.i = call i32 @lt_dlinit() nounwind ; <i32> [#uses=1]
%tobool.i = icmp ne i32 %call.i, 0 ; <i1> [#uses=1]
br i1 %tobool.i, label %if.then.i, label %if.end.i
if.then.i: ; preds = %entry
%call1.i = call i32 @warn_dlerror(i8* getelementptr inbounds ([45 x i8]* @.str76843, i32 0, i32 0)) nounwind ; <i32> [#uses=0]
store i32 -1, i32* %retval.i
br label %lt_init.exit
if.end.i: ; preds = %entry
store i32 0, i32* %retval.i
br label %lt_init.exit
lt_init.exit: ; preds = %if.end.i, %if.then.i
%3 = load i32* %retval.i ; <i32> [#uses=1]
call void asm sideeffect "cpuid", "~{ax},~{bx},~{cx},~{dx},~{memory},~{dirflag},~{fpsr},~{flags}"() nounwind
%4 = call i64 @llvm.readcyclecounter() nounwind ; <i64> [#uses=1]
%5 = sub i64 %4, %2 ; <i64> [#uses=1]
%6 = call i64 @llvm.atomic.load.add.i64.p0i64(i64* getelementptr inbounds ([1216 x i64]* @__profiling_callsite_timestamps_live, i32 0, i32 51), i64 %5) nounwind ; <i64> [#uses=0]
;CHECK: lock
;CHECK-NEXT: {{xadd|addq}} %rdx, __profiling_callsite_timestamps_live
;CHECK-NEXT: cmpl $0,
;CHECK-NEXT: jne
%cmp = icmp eq i32 %3, 0 ; <i1> [#uses=1]
br i1 %cmp, label %if.then, label %if.end
if.then: ; preds = %lt_init.exit
call void @cli_rarload()
br label %if.end
if.end: ; preds = %if.then, %lt_init.exit
store i32 0, i32* %retval
%7 = load i32* %retval ; <i32> [#uses=1]
tail call void asm sideeffect "cpuid", "~{ax},~{bx},~{cx},~{dx},~{memory},~{dirflag},~{fpsr},~{flags}"() nounwind
%8 = tail call i64 @llvm.readcyclecounter() nounwind ; <i64> [#uses=1]
%9 = sub i64 %8, %0 ; <i64> [#uses=1]
%10 = call i64 @llvm.atomic.load.add.i64.p0i64(i64* getelementptr inbounds ([1216 x i64]* @__profiling_callsite_timestamps_live, i32 0, i32 50), i64 %9) ; <i64> [#uses=0]
ret i32 %7
}
declare void @cli_rarload() nounwind
declare i32 @lt_dlinit()
declare i32 @warn_dlerror(i8*) nounwind
declare i64 @llvm.atomic.load.add.i64.p0i64(i64* nocapture, i64) nounwind
declare i64 @llvm.readcyclecounter() nounwind