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From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Alexei Fedorov <Alexei.Fedorov@arm.com>
Cc: Evan Lloyd <Evan.Lloyd@arm.com>,
	"edk2-devel@lists.01.org" <edk2-devel@lists.01.org>,
	 "leif.lindholm@linaro.org@arm.com"
	<"leif.lindholm@linaro.org"@arm.com>,
	 "nd@arm.com@arm.com" <"nd@arm.com"@arm.com>,
	 "ard.biesheuvel@linaro.org@arm.com"
	<"ard.biesheuvel@linaro.org"@arm.com>,
	 "Matteo.Carlini@arm.com@arm.com"
	<"Matteo.Carlini@arm.com"@arm.com>
Subject: Re: [PATCH 04/19] ArmPlatformPkg: LcdGraphicsOurputDxe: Add debug asserts
Date: Thu, 7 Dec 2017 15:10:05 +0000	[thread overview]
Message-ID: <CAKv+Gu-RSuKacK7=dXoDRkUpsB+62PntxzjKb_PEAeTJMphrzw@mail.gmail.com> (raw)
In-Reply-To: <DB5PR08MB1014DCA9BDE42C4EA8FB61339A330@DB5PR08MB1014.eurprd08.prod.outlook.com>

On 7 December 2017 at 14:55, Alexei Fedorov <Alexei.Fedorov@arm.com> wrote:
> Hi,
>
> I've compiled current HdLcd.c code with different optimisation levels for
> DEBUG build using GCC 7.2.1, and the assembler code below was generated for:
>
>   ASSERT_EFI_ERROR (Status);
>   if (EFI_ERROR( Status )) {
>     return EFI_DEVICE_ERROR;
>   }
>
> -O0 (default DEBUG option for AARCH64 before Ard's patch):
>
>
>     str    x0, [x29, 72]    //, Status
>
> // r:\edk2\ArmPlatformPkg\Drivers\LcdGraphicsOutputDxe\HdLcd.c:79:
> ASSERT_EFI_ERROR (Status);
>     .loc 1 79 0
>     bl    DebugAssertEnabled    //
>     and    w0, w0, 255    // _1, tmp150
>     cmp    w0, 0    // _1,
>     beq    .L4    //,
>     ldr    x0, [x29, 72]    // Status.9_2, Status
>     cmp    x0, 0    // Status.9_2,
>     bge    .L4    //,
>
> 2.  -Os:
>
>      mov    x19, x0    // Status,
> // r:\edk2\ArmPlatformPkg\Drivers\LcdGraphicsOutputDxe\HdLcd.c:79:
> ASSERT_EFI_ERROR (Status);
>     .loc 1 79 0
>     bl    DebugAssertEnabled    //
> .LVL15:
>     tst    w0, 255    //
>     beq    .L4    //,
>     tbz    x19, #63, .L8    // Status,
>
> 3.  -O3:
>
>     mov    x19, x0    // Status,
> .LVL14:
> // r:\edk2\ArmPlatformPkg\Drivers\LcdGraphicsOutputDxe\HdLcd.c:79:
> ASSERT_EFI_ERROR (Status);
>     bl    DebugAssertEnabled    //
> .LVL15:
>     tst    w0, 255    //
>     beq    .L5    //,
>     tbnz    x19, #63, .L26    // Status,
>
> with DebugAssertEnabled() compiled as:
>
> DebugAssertEnabled:
> .LFB4:
>     .loc 1 203 0
>     .cfi_startproc
> // r:\edk2\MdePkg\Library\BaseDebugLibSerialPort\DebugLib.c:204:   return
> (BOOLEAN) ((PcdGet8(PcdDebugPropertyMask) &
> DEBUG_PROPERTY_DEBUG_ASSERT_ENABLED) != 0);
>     .loc 1 204 0
>     adrp    x0, _gPcd_FixedAtBuild_PcdDebugPropertyMask    // tmp80,
>     add    x0, x0, :lo12:_gPcd_FixedAtBuild_PcdDebugPropertyMask    //
> tmp79, tmp80,
>     ldrb    w0, [x0]    // _gPcd_FixedAtBuild_PcdDebugPropertyMask.4_1,
> _gPcd_FixedAtBuild_PcdDebugPropertyMask
>     and    w0, w0, 1    // _3, _2,
>     cmp    w0, 0    // _3,
>     cset    w0, ne    // tmp82,
>     and    w0, w0, 255    // _4, tmp81
> // r:\edk2\MdePkg\Library\BaseDebugLibSerialPort\DebugLib.c:205: }
>     .loc 1 205 0
>     ret
>
> As you can see each "ASSERT_EFI_ERROR (Status)" macro requires
> DebugAssertEnabled() call taking 8 instructions by itself + minimum 3
> instructions (for -Os, -O3) for Status check, which will be performed by "if
> (EFI_ERROR( Status ))" anyway.
> Please correct me if I'm wrong assuming that placing
> ASSERT_EFI_ERROR (Status)
> inside
> if (EFI_ERROR( Status )) {
> statement is an optimisation improvement.
>

Thanks for digging this up. This appears to be an oversight in the
definition of the ASSERT_EFI_ERROR () macro, which is currently
defined as

#if !defined(MDEPKG_NDEBUG)
  #define ASSERT_EFI_ERROR(StatusParameter)                              \
    do {                                                                 \
      if (DebugAssertEnabled ()) {                                       \
        if (EFI_ERROR (StatusParameter)) {                               \

which is obviously the wrong way around, given that the compiler can
never optimize away the function call, due to its potential side
effects (which it doesn't have)

So I will propose to fix this, by swapping the two if () statements.
Please let me know if the issue is still reproducible with that patch
applied.


  reply	other threads:[~2017-12-07 15:05 UTC|newest]

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-26 20:15 [PATCH 00/19] ArmPlatformPkg: Update GOP evan.lloyd
2017-09-26 20:15 ` [PATCH 01/19] ArmPlatformPkg: Tidy LcdGraphicsOutputDxe code: Coding standard evan.lloyd
2017-10-12 18:45   ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 02/19] ArmPlatformPkg: Tidy LcdGraphicsOutputDxe code: Added comments evan.lloyd
2017-10-12 19:02   ` Leif Lindholm
2017-12-05 18:55     ` Evan Lloyd
2017-12-05 19:58       ` Leif Lindholm
2017-12-05 22:06         ` Evan Lloyd
2017-09-26 20:15 ` [PATCH 03/19] ArmPlatformPkg: PL111 and HDLCD: add const qualifier evan.lloyd
2017-10-12 19:07   ` Leif Lindholm
2017-10-12 19:47   ` Ard Biesheuvel
2017-12-01 16:17     ` Evan Lloyd
2017-12-01 17:31       ` Ard Biesheuvel
2017-12-05 20:35         ` Evan Lloyd
2017-12-05 20:54           ` Ard Biesheuvel
2017-09-26 20:15 ` [PATCH 04/19] ArmPlatformPkg: LcdGraphicsOurputDxe: Add debug asserts evan.lloyd
2017-10-12 19:32   ` Leif Lindholm
2017-10-13  7:33   ` Ard Biesheuvel
2017-12-01 16:33     ` Evan Lloyd
2017-12-01 17:34       ` Ard Biesheuvel
2017-12-01 17:58         ` Leif Lindholm
2017-12-05 20:46         ` Evan Lloyd
2017-12-07 14:55           ` Alexei Fedorov
2017-12-07 15:10             ` Ard Biesheuvel [this message]
2017-12-07 16:53               ` Alexei Fedorov
2017-12-08 21:39                 ` Ard Biesheuvel
2017-09-26 20:15 ` [PATCH 05/19] ArmPlatformPkg: PL111LcdArmVExpressLib: Minor code cleanup evan.lloyd
2017-10-12 19:33   ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 06/19] ArmPlatformPkg: PL111Lcd: Replace magic number with macro evan.lloyd
2017-10-12 19:34   ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 07/19] ArmPlatformPkg: PL111LcdArmVExpressLib: Use FixedPcdGet32 evan.lloyd
2017-10-12 19:35   ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 08/19] ArmPlatformPkg: PL11LcdArmVExpressLib: Improvement conditional evan.lloyd
2017-10-12 19:36   ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 09/19] ArmPlatformPkg: HdLcdArmVExpressLib: Use FixedPcdGet32 evan.lloyd
2017-10-12 19:38   ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 10/19] ArmPlatformPkg: HdLcdArmVExpressLib: Remove status check EFI_TIMEOUT evan.lloyd
2017-10-12 19:40   ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 11/19] ArmPlatformPkg: Implement LcdIdentify function for HDLCD GOP evan.lloyd
2017-10-12 19:43   ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 12/19] ArmPlatformPkg: Redefine LcdPlatformGetTimings function evan.lloyd
2017-10-13  7:49   ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 13/19] ArmPlatformPkg: HdLcd Remove redundant Bpp evan.lloyd
2017-10-13  7:53   ` Leif Lindholm
2017-10-17 14:32     ` Evan Lloyd
2017-10-17 15:40       ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 14/19] ArmPlatformPkg: Add PCD to select pixel format evan.lloyd
2017-10-25 14:27   ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 15/19] ArmPlatformPkg: PCD to swap red/blue format for HDLCD evan.lloyd
2017-10-25 14:33   ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 16/19] ArmPlatformPkg: Reorganize Lcd Graphics Output evan.lloyd
2017-10-25 14:44   ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 17/19] ArmPlatformPkg: Additional display modes evan.lloyd
2017-10-25 14:45   ` Leif Lindholm
2017-09-26 20:15 ` [PATCH 18/19] ArmPlatformPkg: Reserving framebuffer at build evan.lloyd
2017-10-25 14:51   ` Leif Lindholm
2017-10-25 18:10   ` Ard Biesheuvel
2017-12-01 16:56     ` Evan Lloyd
2017-12-01 17:38       ` Ard Biesheuvel
2017-09-26 20:15 ` [PATCH 19/19] ArmPlatformPkg: New DP500/DP550/DP650 GOP driver evan.lloyd
2017-10-25 15:31   ` Leif Lindholm
2017-11-28 18:17   ` Ard Biesheuvel
2017-12-01 13:12     ` Evan Lloyd
2017-12-01 17:18       ` Ard Biesheuvel
2017-12-05 20:03         ` Evan Lloyd
2017-12-05 21:27           ` Ard Biesheuvel
2017-12-07 20:21             ` Evan Lloyd
2017-12-07 21:10               ` Ard Biesheuvel
2017-12-01 17:29       ` Leif Lindholm

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