[X86] PR32755 : Improvement in CodeGen instruction selection for LEAs.

Summary:
   1/  Operand folding during complex pattern matching for LEAs has been
       extended, such that it promotes Scale to accommodate similar operand
       appearing in the DAG.
       e.g.
          T1 = A + B
          T2 = T1 + 10
          T3 = T2 + A
       For above DAG rooted at T3, X86AddressMode will no look like
          Base = B , Index = A , Scale = 2 , Disp = 10

   2/  During OptimizeLEAPass down the pipeline factorization is now performed over LEAs
       so that if there is an opportunity then complex LEAs (having 3 operands)
       could be factored out.
       e.g.
          leal 1(%rax,%rcx,1), %rdx
          leal 1(%rax,%rcx,2), %rcx
       will be factored as following
          leal 1(%rax,%rcx,1), %rdx
          leal (%rdx,%rcx)   , %edx

   3/ Aggressive operand folding for AM based selection for LEAs is sensitive to loops,
      thus avoiding creation of any complex LEAs within a loop.

Reviewers: lsaba, RKSimon, craig.topper, qcolombet

Reviewed By: lsaba

Subscribers: spatel, igorb, llvm-commits

Differential Revision: https://reviews.llvm.org/D35014

llvm-svn: 313343

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 48dc09339a6..aa4b88808f3 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -26,6 +26,7 @@
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/BranchProbabilityInfo.h"
 #include "llvm/Analysis/CFG.h"
+#include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/OptimizationDiagnosticInfo.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/CodeGen/FastISel.h"
@@ -325,6 +326,8 @@ void SelectionDAGISel::getAnalysisUsage(AnalysisUsage &AU) const {
   if (OptLevel != CodeGenOpt::None)
     AU.addRequired<AAResultsWrapperPass>();
   AU.addRequired<GCModuleInfo>();
+  if (OptLevel != CodeGenOpt::None)
+    AU.addRequired<LoopInfoWrapperPass>();
   AU.addRequired<StackProtector>();
   AU.addPreserved<StackProtector>();
   AU.addPreserved<GCModuleInfo>();
@@ -1419,6 +1422,7 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) {
 
   // Iterate over all basic blocks in the function.
   for (const BasicBlock *LLVMBB : RPOT) {
+    CurDAG->IsDAGPartOfLoop = false;
     if (OptLevel != CodeGenOpt::None) {
       bool AllPredsVisited = true;
       for (const_pred_iterator PI = pred_begin(LLVMBB), PE = pred_end(LLVMBB);
@@ -1596,6 +1600,13 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) {
                                    FunctionBasedInstrumentation);
     }
 
+    if (OptLevel != CodeGenOpt::None) {
+      auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
+      LoopInfo &LI = LIWP.getLoopInfo();
+      if (LI.getLoopFor(LLVMBB))
+        CurDAG->IsDAGPartOfLoop = true;
+    }
+
     if (Begin != BI)
       ++NumDAGBlocks;
     else