Temporarily disable on-demand fast-isel.

llvm-svn: 107393

2 files changed, 14 insertions, 8 deletions

diff --git a/llvm/lib/CodeGen/LLVMTargetMachine.cpp b/llvm/lib/CodeGen/LLVMTargetMachine.cpp
index bf3137e4953..d437370031d 100644
--- a/llvm/lib/CodeGen/LLVMTargetMachine.cpp
+++ b/llvm/lib/CodeGen/LLVMTargetMachine.cpp
@@ -329,15 +329,19 @@ bool LLVMTargetMachine::addCommonCodeGenPasses(PassManagerBase &PM,
   if (OptLevel != CodeGenOpt::None)
     PM.add(createOptimizePHIsPass());
 
-  if (OptLevel != CodeGenOpt::None) {
-    // With optimization, dead code should already be eliminated. However
-    // there is one known exception: lowered code for arguments that are only
-    // used by tail calls, where the tail calls reuse the incoming stack
-    // arguments directly (see t11 in test/CodeGen/X86/sibcall.ll).
-    PM.add(createDeadMachineInstructionElimPass());
-    printAndVerify(PM, "After codegen DCE pass",
-                   /* allowDoubleDefs= */ true);
+  // Delete dead machine instructions regardless of optimization level.
+  //
+  // At -O0, fast-isel frequently creates dead instructions.
+  //
+  // With optimization, dead code should already be eliminated. However
+  // there is one known exception: lowered code for arguments that are only
+  // used by tail calls, where the tail calls reuse the incoming stack
+  // arguments directly (see t11 in test/CodeGen/X86/sibcall.ll).
+  PM.add(createDeadMachineInstructionElimPass());
+  printAndVerify(PM, "After codegen DCE pass",
+                 /* allowDoubleDefs= */ true);
 
+  if (OptLevel != CodeGenOpt::None) {
     PM.add(createOptimizeExtsPass());
     if (!DisableMachineLICM)
       PM.add(createMachineLICMPass());
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 073e2964d20..94f0efcb70a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -709,11 +709,13 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) {
       FastIS->startNewBlock(BB);
       // Do FastISel on as many instructions as possible.
       for (; BI != End; ++BI) {
+#if 0
         // Defer instructions with no side effects; they'll be emitted
         // on-demand later.
         if (BI->isSafeToSpeculativelyExecute() &&
             !FuncInfo->isExportedInst(BI))
           continue;
+#endif
 
         // Try to select the instruction with FastISel.
         if (FastIS->SelectInstruction(BI))