[PassBuilder][PassManagerBuilder] Run LICM before loop spawning to ensure loop-invariant conditions appear outside of the loop. Addresses llvm#66.

Author: neboat

llvm/lib/Passes/PassBuilderPipelines.cpp

@@ -1336,7 +1336,8 @@ PassBuilder::buildTapirLoweringPipeline(OptimizationLevel Level,
   // Rotate Loop - disable header duplication at -Oz
   LPM1.addPass(LoopRotatePass(Level != OptimizationLevel::Oz));
   LPM2.addPass(IndVarSimplifyPass());
-  LPM2.addPass(LICMPass(PTO.LicmMssaOptCap, PTO.LicmMssaNoAccForPromotionCap));
+  LPM2.addPass(LICMPass(PTO.LicmMssaOptCap, PTO.LicmMssaNoAccForPromotionCap,
+                        /*AllowSpeculation=*/true));
 
   FunctionPassManager FPM;
   FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM1),

llvm/lib/Transforms/IPO/PassManagerBuilder.cpp

@@ -1087,6 +1087,7 @@ void PassManagerBuilder::populateModulePassManager(
     // rotated form due to GVN or other transformations, and loop spawning
     // relies on the rotated form.  Disable header duplication at -Oz.
     MPM.add(createLoopRotatePass(SizeLevel == 2 ? 0 : -1));
+    MPM.add(createLICMPass(LicmMssaOptCap, LicmMssaNoAccForPromotionCap));
     // Outline Tapir loops as needed.
     MPM.add(createLoopSpawningTIPass());
     if (VerifyTapir)