From 07bd9c06aa2823cf056757534b6ffa27ddd34137 Mon Sep 17 00:00:00 2001
From: RSDuck <RSDuck@users.noreply.github.com>
Date: Mon, 17 Apr 2023 20:53:41 +0200
Subject: [PATCH] fix UB also misc changes to use more unsigned multiplication
 also fix framebuffer resize

---
 src/GPU3D_Compute.cpp       |  6 ++++--
 src/GPU3D_Compute.h         |  2 +-
 src/GPU3D_Compute_shaders.h | 16 ++++++++--------
 3 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/src/GPU3D_Compute.cpp b/src/GPU3D_Compute.cpp
index 5421708e..bfb10e92 100644
--- a/src/GPU3D_Compute.cpp
+++ b/src/GPU3D_Compute.cpp
@@ -89,7 +89,6 @@ bool ComputeRenderer::Init()
     glGenBuffers(1, &TileMemory);
 
     glGenTextures(1, &YSpanIndicesTexture);
-    glGenTextures(1, &Framebuffer);
     glGenTextures(1, &LowResFramebuffer);
     glBindTexture(GL_TEXTURE_2D, LowResFramebuffer);
     glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA8UI, 256, 192);
@@ -230,6 +229,9 @@ void ComputeRenderer::SetRenderSettings(GPU::RenderSettings& settings)
     glBindBuffer(GL_SHADER_STORAGE_BUFFER, BinResultMemory);
     glBufferData(GL_SHADER_STORAGE_BUFFER, binResultSize, nullptr, GL_DYNAMIC_DRAW);
 
+    if (Framebuffer != 0)
+        glDeleteTextures(1, &Framebuffer);
+    glGenTextures(1, &Framebuffer);
     glBindTexture(GL_TEXTURE_2D, Framebuffer);
     glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA8, ScreenWidth, ScreenHeight);
 
@@ -1391,7 +1393,7 @@ void ComputeRenderer::RenderFrame()
             for (int i = 0; i < numVariants; i++)
             {
                 GLuint shader = 0;
-                if (variants[i].Texture == -1)
+                if (variants[i].Texture == 0)
                 {
                     shader = shadersNoTexture[variants[i].BlendMode];
                 }
diff --git a/src/GPU3D_Compute.h b/src/GPU3D_Compute.h
index 7a3af101..fc1b7c00 100644
--- a/src/GPU3D_Compute.h
+++ b/src/GPU3D_Compute.h
@@ -213,7 +213,7 @@ private:
 
     u32 TextureDecodingBuffer[1024*1024];
 
-    GLuint Framebuffer;
+    GLuint Framebuffer = 0;
     GLuint LowResFramebuffer;
     GLuint PixelBuffer;
 
diff --git a/src/GPU3D_Compute_shaders.h b/src/GPU3D_Compute_shaders.h
index 26e7adeb..65ec4f12 100644
--- a/src/GPU3D_Compute_shaders.h
+++ b/src/GPU3D_Compute_shaders.h
@@ -299,11 +299,11 @@ uint Div64_32_32(uint numHi, uint numLo, uint den)
     // there's a 1 in the MSB.
     // We also shift numer by the same amount. This cannot overflow because numHi < den.
     // The expression (-shift & 63) is the same as (64 - shift), except it avoids the UB of shifting
-    // by 64. <---- in C. I'm pretty sure shifts are masked in GLSL, but whatever.
+    // by 64. (it's also UB in GLSL!!!!)
     uint shift = 31 - findMSB(den);
     den <<= shift;
     numHi <<= shift;
-    numHi |= (numLo >> (-shift & 63U)) & uint(-int(shift) >> 63);
+    numHi |= (numLo >> (-shift & 31U)) & uint(-int(shift) >> 31);
     numLo <<= shift;
 
     // Extract the low digits of the numerator and both digits of the denominator.
@@ -347,12 +347,12 @@ int CalcYFactorY(YSpanSetup span, int i)
     /*
         maybe it would be better to do use a 32x32=64 multiplication?
     */
-    uint numLo = abs(i * span.W0n);
+    uint numLo = uint(abs(i)) * uint(span.W0n);
     uint numHi = 0U;
-    numHi |= numLo >> (32-YFactorShift);
+    numHi |= numLo >> (32U-YFactorShift);
     numLo <<= YFactorShift;
 
-    uint den = abs(i * span.W0d + (span.I1 - span.I0 - i) * span.W1d);
+    uint den = uint(abs(i)) * uint(span.W0d) + uint(abs(span.I1 - span.I0 - i)) * span.W1d;
 
     if (den == 0)
     {
@@ -370,12 +370,12 @@ int CalcYFactorX(XSpanSetup span, int x)
 
     if (span.X0 != span.X1)
     {
-        uint numLo = uint(x) * span.W0;
+        uint numLo = uint(x) * uint(span.W0);
         uint numHi = 0U;
-        numHi |= numLo >> (32-YFactorShift);
+        numHi |= numLo >> (32U-YFactorShift);
         numLo <<= YFactorShift;
 
-        uint den = (uint(x) * span.W0) + (uint(span.X1 - span.X0 - x) * span.W1);
+        uint den = uint(x) * uint(span.W0) + uint(span.X1 - span.X0 - x) * uint(span.W1);
 
         if (den == 0)
             return 0;