Mesa (master): nir: Fix nir_validate fail after nir_lower_tex

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Module: Mesa
Branch: master
Commit: f6359d2dc32d625319921d7232197764907bb5a4
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=f6359d2dc32d625319921d7232197764907bb5a4

Author: Rob Clark <robdclark at chromium.org>
Date:   Wed Nov 11 16:59:04 2020 -0800

nir: Fix nir_validate fail after nir_lower_tex

It is UB to initialize unions on the stack and rely on bits not covered
by the initialized union member to be zero.  Lets just simplify it and
move the entire nir_const_value off the stack.

While we're in there, sprinkle around some const.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/3778
Signed-off-by: Rob Clark <robdclark at chromium.org>
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7579>

---

 src/compiler/nir/nir_lower_tex.c | 63 ++++++++++++++++++++--------------------
 1 file changed, 31 insertions(+), 32 deletions(-)

diff --git a/src/compiler/nir/nir_lower_tex.c b/src/compiler/nir/nir_lower_tex.c
index 4f5e1805e8b..15a8c1b42af 100644
--- a/src/compiler/nir/nir_lower_tex.c
+++ b/src/compiler/nir/nir_lower_tex.c
@@ -40,29 +40,33 @@
 #include "nir_builtin_builder.h"
 #include "nir_format_convert.h"
 
-static float bt601_csc_coeffs[9] = {
-   1.16438356f,  1.16438356f, 1.16438356f,
-   0.0f,        -0.39176229f, 2.01723214f,
-   1.59602678f, -0.81296764f, 0.0f,
-};
-static float bt709_csc_coeffs[9] = {
-   1.16438356f,  1.16438356f, 1.16438356f,
-   0.0f       , -0.21324861f, 2.11240179f,
-   1.79274107f, -0.53290933f, 0.0f,
-};
-static float bt2020_csc_coeffs[9] = {
-   1.16438356f,  1.16438356f, 1.16438356f,
-   0.0f       , -0.18732610f, 2.14177232f,
-   1.67867411f, -0.65042432f, 0.0f,
-};
-
-static float bt601_csc_offsets[3] = {
+typedef struct nir_const_value_3_4 {
+   nir_const_value v[3][4];
+} nir_const_value_3_4;
+
+static const nir_const_value_3_4 bt601_csc_coeffs = { {
+   { { .f32 = 1.16438356f }, { .f32 =  1.16438356f }, { .f32 = 1.16438356f } },
+   { { .f32 = 0.0f        }, { .f32 = -0.39176229f }, { .f32 = 2.01723214f } },
+   { { .f32 = 1.59602678f }, { .f32 = -0.81296764f }, { .f32 = 0.0f        } },
+} };
+static const nir_const_value_3_4 bt709_csc_coeffs = { {
+   { { .f32 = 1.16438356f }, { .f32 =  1.16438356f }, { .f32 = 1.16438356f } },
+   { { .f32 = 0.0f        }, { .f32 = -0.21324861f }, { .f32 = 2.11240179f } },
+   { { .f32 = 1.79274107f }, { .f32 = -0.53290933f }, { .f32 = 0.0f        } },
+} };
+static const nir_const_value_3_4 bt2020_csc_coeffs = { {
+   { { .f32 = 1.16438356f }, { .f32 =  1.16438356f }, { .f32 = 1.16438356f } },
+   { { .f32 = 0.0f        }, { .f32 = -0.18732610f }, { .f32 = 2.14177232f } },
+   { { .f32 = 1.67867411f }, { .f32 = -0.65042432f }, { .f32 = 0.0f        } },
+} };
+
+static const float bt601_csc_offsets[3] = {
    -0.874202218f, 0.531667823f, -1.085630789f
 };
-static float bt709_csc_offsets[3] = {
+static const float bt709_csc_offsets[3] = {
    -0.972945075f, 0.301482665f, -1.133402218f
 };
-static float bt2020_csc_offsets[3] = {
+static const float bt2020_csc_offsets[3] = {
    -0.915687932f, 0.347458499f, -1.148145075f
 };
 
@@ -286,25 +290,20 @@ convert_yuv_to_rgb(nir_builder *b, nir_tex_instr *tex,
                    const nir_lower_tex_options *options)
 {
 
-   float *offset_vals;
-   float *m_vals;
+   const float *offset_vals;
+   const nir_const_value_3_4 *m;
    assert((options->bt709_external & options->bt2020_external) == 0);
    if (options->bt709_external & (1 << tex->texture_index)) {
-      m_vals = bt709_csc_coeffs;
+      m = &bt709_csc_coeffs;
       offset_vals = bt709_csc_offsets;
    } else if (options->bt2020_external & (1 << tex->texture_index)) {
-      m_vals = bt2020_csc_coeffs;
+      m = &bt2020_csc_coeffs;
       offset_vals = bt2020_csc_offsets;
    } else {
-      m_vals = bt601_csc_coeffs;
+      m = &bt601_csc_coeffs;
       offset_vals = bt601_csc_offsets;
    }
 
-   nir_const_value m[3][4] = {
-      { { .f32 = m_vals[0] }, { .f32 =  m_vals[1] }, { .f32 = m_vals[2] }, { .f32 = 0.0f } },
-      { { .f32 = m_vals[3] }, { .f32 =  m_vals[4] }, { .f32 = m_vals[5] }, { .f32 = 0.0f } },
-      { { .f32 = m_vals[6] }, { .f32 =  m_vals[7] }, { .f32 = m_vals[8] }, { .f32 = 0.0f } },
-   };
    unsigned bit_size = nir_dest_bit_size(tex->dest);
 
    nir_ssa_def *offset =
@@ -316,9 +315,9 @@ convert_yuv_to_rgb(nir_builder *b, nir_tex_instr *tex,
 
    offset = nir_f2fN(b, offset, bit_size);
 
-   nir_ssa_def *m0 = nir_f2fN(b, nir_build_imm(b, 4, 32, m[0]), bit_size);
-   nir_ssa_def *m1 = nir_f2fN(b, nir_build_imm(b, 4, 32, m[1]), bit_size);
-   nir_ssa_def *m2 = nir_f2fN(b, nir_build_imm(b, 4, 32, m[2]), bit_size);
+   nir_ssa_def *m0 = nir_f2fN(b, nir_build_imm(b, 4, 32, m->v[0]), bit_size);
+   nir_ssa_def *m1 = nir_f2fN(b, nir_build_imm(b, 4, 32, m->v[1]), bit_size);
+   nir_ssa_def *m2 = nir_f2fN(b, nir_build_imm(b, 4, 32, m->v[2]), bit_size);
 
    nir_ssa_def *result =
       nir_ffma(b, y, m0, nir_ffma(b, u, m1, nir_ffma(b, v, m2, offset)));