linux-kernel - Re: [PATCH] drm/amdgpu: Initialize shadow to false in gfx_v9_0_rlcg

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Date:   Wed, 18 Mar 2020 13:26:44 -0700
From:   Joe Perches <joe@...ches.com>
To:     Nathan Chancellor <natechancellor@...il.com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH] drm/amdgpu: Initialize shadow to false in
 gfx_v9_0_rlcg_wreg

On Tue, 2020-03-17 at 17:25 -0700, Nathan Chancellor wrote:
> clang warns:
> 
> drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:754:6: warning: variable 'shadow'
> is used uninitialized whenever 'if' condition is
> false [-Wsometimes-uninitialized]
>         if (offset == grbm_cntl || offset == grbm_idx)
>             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:757:6: note: uninitialized use
> occurs here
>         if (shadow) {
>             ^~~~~~

Wouldn't it be better to get rid of the shadow variable completely?
---
 drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
index 7bc248..496b9e 100644
--- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
@@ -735,7 +735,6 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)
 	static void *spare_int;
 	static uint32_t grbm_cntl;
 	static uint32_t grbm_idx;
-	bool shadow;
 
 	scratch_reg0 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG0_BASE_IDX] + mmSCRATCH_REG0)*4;
 	scratch_reg1 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG1_BASE_IDX] + mmSCRATCH_REG1)*4;
@@ -751,10 +750,7 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)
 		return;
 	}
 
-	if (offset == grbm_cntl || offset == grbm_idx)
-		shadow = true;
-
-	if (shadow) {
+	if (offset == grbm_cntl || offset == grbm_idx) {
 		if (offset  == grbm_cntl)
 			writel(v, scratch_reg2);
 		else if (offset == grbm_idx)