Add options to speedup compilation. (#4240)

* Add options to speedup compilation.

* Fix.

* Plumb options to DCE pass.

* Revert debug change.

* Fix regressions.

* More optimizations.

* more cleanup and fixes.

* remove comment.

* Fixes.

* Another fix.

* Fix errors.

* Fix errors.

* Add comments.

1 files changed, 17 insertions, 10 deletions

diff --git a/source/slang/slang-ir-ssa-simplification.cpp b/source/slang/slang-ir-ssa-simplification.cpp
index a0224cea5..6c02734b5 100644
--- a/source/slang/slang-ir-ssa-simplification.cpp
+++ b/source/slang/slang-ir-ssa-simplification.cpp
@@ -45,6 +45,8 @@ namespace Slang
         const int kMaxIterations = 8;
         const int kMaxFuncIterations = 16;
         int iterationCounter = 0;
+        IRDeadCodeEliminationOptions dceOptions = IRDeadCodeEliminationOptions();
+        dceOptions.useFastAnalysis = options.minimalOptimization;
 
         while (changed && iterationCounter < kMaxIterations)
         {
@@ -74,20 +76,19 @@ namespace Slang
                     if (!options.minimalOptimization)
                         funcChanged |= removeRedundancyInFunc(func);
                     funcChanged |= simplifyCFG(func, options.cfgOptions);
-                    eliminateDeadCode(func);
-                    funcChanged |= constructSSA(func);
+                    // Note: we disregard the `changed` state from dead code elimination pass since
+                    // SCCP pass could be generating temporarily evaluated constant values and never actually use them.
+                    // DCE will always remove those nearly generated consts and always returns true here.
+                    eliminateDeadCode(func, dceOptions);
+                    if (funcIterationCount == 0)
+                        funcChanged |= constructSSA(func);
                     changed |= funcChanged;
                     funcIterationCount++;
                 }
             }
-
-            // Note: we disregard the `changed` state from dead code elimination pass since
-            // SCCP pass could be generating temporarily evaluated constant values and never actually use them.
-            // DCE will always remove those nearly generated consts and always returns true here.
-            eliminateDeadCode(module);
-
             iterationCounter++;
         }
+        eliminateDeadCode(module, dceOptions);
     }
 
     void simplifyNonSSAIR(TargetProgram* target, IRModule* module, IRSimplificationOptions options)
@@ -95,6 +96,9 @@ namespace Slang
         bool changed = true;
         const int kMaxIterations = 8;
         int iterationCounter = 0;
+        IRDeadCodeEliminationOptions dceOptions = IRDeadCodeEliminationOptions();
+        dceOptions.useFastAnalysis = options.minimalOptimization;
+
         while (changed && iterationCounter < kMaxIterations)
         {
             changed = false;
@@ -107,7 +111,7 @@ namespace Slang
             // Note: we disregard the `changed` state from dead code elimination pass since
             // SCCP pass could be generating temporarily evaluated constant values and never actually use them.
             // DCE will always remove those nearly generated consts and always returns true here.
-            eliminateDeadCode(module);
+            eliminateDeadCode(module, dceOptions);
             iterationCounter++;
         }
     }
@@ -115,6 +119,9 @@ namespace Slang
 
     void simplifyFunc(TargetProgram* target, IRGlobalValueWithCode* func, IRSimplificationOptions options, DiagnosticSink* sink)
     {
+        IRDeadCodeEliminationOptions dceOptions = IRDeadCodeEliminationOptions();
+        dceOptions.useFastAnalysis = options.minimalOptimization;
+
         bool changed = true;
         const int kMaxIterations = 8;
         int iterationCounter = 0;
@@ -133,7 +140,7 @@ namespace Slang
             // Note: we disregard the `changed` state from dead code elimination pass since
             // SCCP pass could be generating temporarily evaluated constant values and never actually use them.
             // DCE will always remove those nearly generated consts and always returns true here.
-            eliminateDeadCode(func);
+            eliminateDeadCode(func, dceOptions);
 
             changed |= constructSSA(func);