Disable SpeculativeDevirtualization at -Os

Author: aschwaighofer

lib/SILOptimizer/Transforms/SpeculativeDevirtualizer.cpp

@@ -556,6 +556,13 @@ namespace {
     ~SpeculativeDevirtualization() override {}
 
     void run() override {
+
+      auto &CurFn = *getFunction();
+      // Don't perform speculative devirtualization at -Os.
+      if (CurFn.getModule().getOptions().Optimization ==
+          SILOptions::SILOptMode::OptimizeForSize)
+        return;
+
       ClassHierarchyAnalysis *CHA = PM->getAnalysis<ClassHierarchyAnalysis>();
 
       bool Changed = false;

test/SILOptimizer/devirt_speculate.swift

@@ -1,4 +1,5 @@
 // RUN: %target-swift-frontend %s -parse-as-library -O -emit-sil | %FileCheck %s
+// RUN: %target-swift-frontend %s -parse-as-library -Osize -emit-sil | %FileCheck %s --check-prefix=OSIZE
 //
 // Test speculative devirtualization.
 
@@ -40,6 +41,10 @@ class Sub7 : Base {
 // CHECK-NOT: checked_cast_br
 // CHECK: %[[CM:[0-9]+]] = class_method %0 : $Base, #Base.foo!1 : (Base) -> () -> (), $@convention(method) (@guaranteed Base) -> ()
 // CHECK: apply %[[CM]](%0) : $@convention(method) (@guaranteed Base) -> ()
+
+// OSIZE: @_T016devirt_speculate28testMaxNumSpeculativeTargetsyAA4BaseCF
+// OSIZE-NOT: checked_cast_br [exact] %0 : $Base to $Base
+// OSIZE-NOT: checked_cast_br [exact] %0 : $Base to $Sub
 public func testMaxNumSpeculativeTargets(_ b: Base) {
   b.foo()
 }