Optimize "max(t, t)" to fold into just "t"

This masks a crash related to nested, unconditional continue statements. Those constructs are known to be buggy, but we have elected to not fix them at this point in time because the SWANGLE project will deprecate all of Swiftshader's GLES backend. It's unlikely that the remaining bug will effect many end-users as it relies on bizarre control flow. For logging purposes here is the shader code that reproduces an infinite loop: void foo() { } void main() { for (int i = 0; i < 4; i++) { continue; for (int k = 0; k < 4; k++) continue; foo(); } } I'm not adding this as a unit test since we aren't fixing our compiler. Bug chromium:997283 Change-Id: Id31d70c4cd70a16fd20b7ebed18a82d5f8a705ba Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/36708Tested-by: Sean Risser <srisser@google.com> Kokoro-Presubmit: kokoro <noreply+kokoro@google.com> Reviewed-by: Alexis Hétu <sugoi@google.com> Reviewed-by: Nicolas Capens <nicolascapens@google.com>

Optimize "max(t, t)" to fold into just "t"
a9dc7707 · Sean Risser · 8b693854 · a9dc7707
Commit a9dc7707 authored Sep 26, 2019 by Sean Risser
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ParseHelper.cpp src/OpenGL/compiler/ParseHelper.cpp +10 -0

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--- a/src/OpenGL/compiler/ParseHelper.cpp
+++ b/src/OpenGL/compiler/ParseHelper.cpp
@@ -3669,6 +3669,16 @@ TIntermTyped *TParseContext::addFunctionCallOrMethod(TFunction *fnCall, TIntermN
 									callNode = typedReturnNode;
 								}
 							}
+							else if (op == EOpMax || op == EOpMin)
+							{
+								TIntermSymbol *leftSymbol = left->getAsSymbolNode();
+								TIntermSymbol *rightSymbol = right->getAsSymbolNode();
+
+								if (leftSymbol && rightSymbol && leftSymbol->getId() == rightSymbol->getId())
+								{
+									callNode = left;
+								}
+							}
 						}
 					}
 				}