[InstCombine] Introducing Aggressive Instruction Combine pass (-aggressive-instcombine).

Combine expression patterns to form expressions with fewer, simple instructions.
This pass does not modify the CFG.

For example, this pass reduce width of expressions post-dominated by TruncInst
into smaller width when applicable.

It differs from instcombine pass in that it contains pattern optimization that
requires higher complexity than the O(1), thus, it should run fewer times than
instcombine pass.

Differential Revision: https://reviews.llvm.org/D38313

llvm-svn: 323321

3 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/Passes/LLVMBuild.txt b/llvm/lib/Passes/LLVMBuild.txt
index e2378a84328..d6e9bf1fcf3 100644
--- a/llvm/lib/Passes/LLVMBuild.txt
+++ b/llvm/lib/Passes/LLVMBuild.txt
@@ -19,4 +19,4 @@
 type = Library
 name = Passes
 parent = Libraries
-required_libraries = Analysis CodeGen Core IPO InstCombine Scalar Support Target TransformUtils Vectorize Instrumentation
+required_libraries = AggressiveInstCombine Analysis CodeGen Core IPO InstCombine Scalar Support Target TransformUtils Vectorize Instrumentation
diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
index 8ea51e04afe..89570f7d153 100644
--- a/llvm/lib/Passes/PassBuilder.cpp
+++ b/llvm/lib/Passes/PassBuilder.cpp
@@ -59,6 +59,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Regex.h"
 #include "llvm/Target/TargetMachine.h"
+#include "llvm/Transforms/AggressiveInstCombine/AggressiveInstCombine.h"
 #include "llvm/Transforms/GCOVProfiler.h"
 #include "llvm/Transforms/IPO/AlwaysInliner.h"
 #include "llvm/Transforms/IPO/ArgumentPromotion.h"
@@ -363,6 +364,8 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
   FPM.addPass(JumpThreadingPass());
   FPM.addPass(CorrelatedValuePropagationPass());
   FPM.addPass(SimplifyCFGPass());
+  if (Level == O3)
+    FPM.addPass(AggressiveInstCombinePass());
   FPM.addPass(InstCombinePass());
 
   if (!isOptimizingForSize(Level))
@@ -1010,6 +1013,8 @@ ModulePassManager PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
   // function pointers.  When this happens, we often have to resolve varargs
   // calls, etc, so let instcombine do this.
   FunctionPassManager PeepholeFPM(DebugLogging);
+  if (Level == O3)
+    PeepholeFPM.addPass(AggressiveInstCombinePass());
   PeepholeFPM.addPass(InstCombinePass());
   invokePeepholeEPCallbacks(PeepholeFPM, Level);
 
diff --git a/llvm/lib/Passes/PassRegistry.def b/llvm/lib/Passes/PassRegistry.def
index 9ac95ee6fa8..bebeb8f2a7e 100644
--- a/llvm/lib/Passes/PassRegistry.def
+++ b/llvm/lib/Passes/PassRegistry.def
@@ -139,6 +139,7 @@ FUNCTION_ALIAS_ANALYSIS("type-based-aa", TypeBasedAA())
 FUNCTION_PASS("aa-eval", AAEvaluator())
 FUNCTION_PASS("adce", ADCEPass())
 FUNCTION_PASS("add-discriminators", AddDiscriminatorsPass())
+FUNCTION_PASS("aggressive-instcombine", AggressiveInstCombinePass())
 FUNCTION_PASS("alignment-from-assumptions", AlignmentFromAssumptionsPass())
 FUNCTION_PASS("bdce", BDCEPass())
 FUNCTION_PASS("bounds-checking", BoundsCheckingPass())