e6459b9e6c
REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1303 Today's code generates assembly code as below for InternalSyncIncrement: __asm__ __volatile__ ( "movl $1, %%eax \n\t" "lock \n\t" "xadd %%eax, %1 \n\t" "inc %%eax \n\t" : "=a" (Result), // %0 "+m" (*Value) // %1 : // no inputs that aren't also outputs : "memory", "cc" ); 0: 55 pushl %ebp 1: 89 e5 movl %esp, %ebp 3: 8b 45 08 movl 8(%ebp), %eax 6: b8 01 00 00 00 movl $1, %eax b: f0 lock c: 0f c1 00 xaddl %eax, _InternalSyncIncrement(%eax) f: 40 incl %eax 10: 5d popl %ebp 11: c3 retl Line #3 and Line #6 both use EAX as destination register. Line #c uses EAX and (EAX). The output operand "=a" tells GCC that EAX is used for output. But GCC only assumes that EAX will be used in the very last instruction. Per GCC document, "Use the '&' constraint modifier on all output operands that must not overlap an input. Otherwise, GCC may allocate the output operand in the same register as an unrelated input operand, on the assumption that the assembler code consumes its inputs before producing outputs. This assumption may be false if the assembler code actually consists of more than one instruction." "=&a" should be used to tell GCC not use EAX before the assembly. Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com> Cc: Liming Gao <liming.gao@intel.com> Cc: Michael Kinney <michael.d.kinney@intel.com> Cc: Laszlo Ersek <lersek@redhat.com> Cc: Philippe Mathieu-Daudé <philmd@redhat.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by: Laszlo Ersek <lersek@redhat.com> Tested-by: Laszlo Ersek <lersek@redhat.com> Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Fixes:8a94eb9283Fixes:17634d026f
207 lines
5.9 KiB
C
207 lines
5.9 KiB
C
/** @file
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GCC inline implementation of BaseSynchronizationLib processor specific functions.
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Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
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Portions copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
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This program and the accompanying materials
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are licensed and made available under the terms and conditions of the BSD License
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which accompanies this distribution. The full text of the license may be found at
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http://opensource.org/licenses/bsd-license.php.
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THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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**/
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/**
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Performs an atomic increment of an 32-bit unsigned integer.
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Performs an atomic increment of the 32-bit unsigned integer specified by
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Value and returns the incremented value. The increment operation must be
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performed using MP safe mechanisms.
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@param Value A pointer to the 32-bit value to increment.
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@return The incremented value.
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**/
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UINT32
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EFIAPI
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InternalSyncIncrement (
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IN volatile UINT32 *Value
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)
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{
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UINT32 Result;
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__asm__ __volatile__ (
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"movl $1, %%eax \n\t"
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"lock \n\t"
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"xadd %%eax, %1 \n\t"
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"inc %%eax \n\t"
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: "=&a" (Result), // %0
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"+m" (*Value) // %1
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: // no inputs that aren't also outputs
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: "memory",
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"cc"
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);
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return Result;
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}
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/**
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Performs an atomic decrement of an 32-bit unsigned integer.
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Performs an atomic decrement of the 32-bit unsigned integer specified by
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Value and returns the decremented value. The decrement operation must be
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performed using MP safe mechanisms.
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@param Value A pointer to the 32-bit value to decrement.
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@return The decremented value.
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**/
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UINT32
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EFIAPI
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InternalSyncDecrement (
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IN volatile UINT32 *Value
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)
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{
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UINT32 Result;
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__asm__ __volatile__ (
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"movl $-1, %%eax \n\t"
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"lock \n\t"
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"xadd %%eax, %1 \n\t"
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"dec %%eax \n\t"
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: "=&a" (Result), // %0
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"+m" (*Value) // %1
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: // no inputs that aren't also outputs
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: "memory",
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"cc"
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);
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return Result;
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}
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/**
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Performs an atomic compare exchange operation on a 16-bit unsigned integer.
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Performs an atomic compare exchange operation on the 16-bit unsigned integer
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specified by Value. If Value is equal to CompareValue, then Value is set to
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ExchangeValue and CompareValue is returned. If Value is not equal to CompareValue,
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then Value is returned. The compare exchange operation must be performed using
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MP safe mechanisms.
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@param Value A pointer to the 16-bit value for the compare exchange
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operation.
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@param CompareValue 16-bit value used in compare operation.
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@param ExchangeValue 16-bit value used in exchange operation.
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@return The original *Value before exchange.
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**/
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UINT16
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EFIAPI
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InternalSyncCompareExchange16 (
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IN OUT volatile UINT16 *Value,
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IN UINT16 CompareValue,
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IN UINT16 ExchangeValue
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)
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{
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__asm__ __volatile__ (
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"lock \n\t"
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"cmpxchgw %2, %1 \n\t"
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: "+a" (CompareValue), // %0
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"+m" (*Value) // %1
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: "r" (ExchangeValue) // %2
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: "memory",
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"cc"
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);
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return CompareValue;
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}
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/**
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Performs an atomic compare exchange operation on a 32-bit unsigned integer.
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Performs an atomic compare exchange operation on the 32-bit unsigned integer
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specified by Value. If Value is equal to CompareValue, then Value is set to
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ExchangeValue and CompareValue is returned. If Value is not equal to CompareValue,
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then Value is returned. The compare exchange operation must be performed using
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MP safe mechanisms.
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@param Value A pointer to the 32-bit value for the compare exchange
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operation.
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@param CompareValue 32-bit value used in compare operation.
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@param ExchangeValue 32-bit value used in exchange operation.
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@return The original *Value before exchange.
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**/
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UINT32
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EFIAPI
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InternalSyncCompareExchange32 (
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IN OUT volatile UINT32 *Value,
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IN UINT32 CompareValue,
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IN UINT32 ExchangeValue
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)
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{
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__asm__ __volatile__ (
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"lock \n\t"
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"cmpxchgl %2, %1 \n\t"
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: "+a" (CompareValue), // %0
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"+m" (*Value) // %1
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: "r" (ExchangeValue) // %2
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: "memory",
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"cc"
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);
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return CompareValue;
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}
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/**
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Performs an atomic compare exchange operation on a 64-bit unsigned integer.
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Performs an atomic compare exchange operation on the 64-bit unsigned integer specified
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by Value. If Value is equal to CompareValue, then Value is set to ExchangeValue and
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CompareValue is returned. If Value is not equal to CompareValue, then Value is returned.
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The compare exchange operation must be performed using MP safe mechanisms.
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@param Value A pointer to the 64-bit value for the compare exchange
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operation.
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@param CompareValue 64-bit value used in compare operation.
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@param ExchangeValue 64-bit value used in exchange operation.
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@return The original *Value before exchange.
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**/
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UINT64
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EFIAPI
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InternalSyncCompareExchange64 (
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IN OUT volatile UINT64 *Value,
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IN UINT64 CompareValue,
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IN UINT64 ExchangeValue
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)
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{
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__asm__ __volatile__ (
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"lock \n\t"
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"cmpxchgq %2, %1 \n\t"
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: "+a" (CompareValue), // %0
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"+m" (*Value) // %1
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: "r" (ExchangeValue) // %2
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: "memory",
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"cc"
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);
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return CompareValue;
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}
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