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());
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))
; CHECK: foo:
; CHECK-NEXT: movq %rdi, -8(%rsp)
; CHECK-NEXT: movq %rsi, -16(%rsp)
-; CHECK-NEXT: movsd 128(%rsi,%rdi,8), %xmm0
+; CHECK: movsd 128(%rsi,%rdi,8), %xmm0
; CHECK-NEXT: ret
define double @foo(i64 %x, double* %p) nounwind {