Revert "Move "auto-init" instructions to the dominator of their users"

This could also move initialization of sret args, causing actually
initialized parts of such return values to be uninitialized. See
discussion on the code review.

> As a result of -ftrivial-auto-var-init, clang generates instructions to
> set alloca'd memory to a given pattern, right after the allocation site.
> In some cases, this (somehow costly) operation could be delayed, leading
> to conditional execution in some cases.
>
> This is not an uncommon situation: it happens ~500 times on the cPython
> code base, and much more on the LLVM codebase. The benefit greatly
> varies on the execution path, but it should not regress on performance.
>
> This is a recommit of cca0100 with
> MemorySSA update fixes.
>
> Differential Revision: https://reviews.llvm.org/D137707

This reverts commit 50b2a11
and follow-up commit ad9ad37.

Author: zmodem

llvm/include/llvm/Transforms/Utils/MoveAutoInit.h

@@ -247,7 +247,6 @@
 #include "llvm/Transforms/Utils/LowerSwitch.h"
 #include "llvm/Transforms/Utils/Mem2Reg.h"
 #include "llvm/Transforms/Utils/MetaRenamer.h"
-#include "llvm/Transforms/Utils/MoveAutoInit.h"
 #include "llvm/Transforms/Utils/NameAnonGlobals.h"
 #include "llvm/Transforms/Utils/PredicateInfo.h"
 #include "llvm/Transforms/Utils/RelLookupTableConverter.h"

llvm/lib/Passes/PassBuilder.cpp

@@ -125,7 +125,6 @@
 #include "llvm/Transforms/Utils/InjectTLIMappings.h"
 #include "llvm/Transforms/Utils/LibCallsShrinkWrap.h"
 #include "llvm/Transforms/Utils/Mem2Reg.h"
-#include "llvm/Transforms/Utils/MoveAutoInit.h"
 #include "llvm/Transforms/Utils/NameAnonGlobals.h"
 #include "llvm/Transforms/Utils/RelLookupTableConverter.h"
 #include "llvm/Transforms/Utils/SimplifyCFGOptions.h"
@@ -656,8 +655,6 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
   FPM.addPass(MemCpyOptPass());
 
   FPM.addPass(DSEPass());
-  FPM.addPass(MoveAutoInitPass());
-
   FPM.addPass(createFunctionToLoopPassAdaptor(
       LICMPass(PTO.LicmMssaOptCap, PTO.LicmMssaNoAccForPromotionCap,
                /*AllowSpeculation=*/true),
@@ -1802,7 +1799,6 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
 
   // Nuke dead stores.
   MainFPM.addPass(DSEPass());
-  MainFPM.addPass(MoveAutoInitPass());
   MainFPM.addPass(MergedLoadStoreMotionPass());
 
   LoopPassManager LPM;

llvm/lib/Passes/PassBuilderPipelines.cpp

@@ -333,7 +333,6 @@ FUNCTION_PASS("mem2reg", PromotePass())
 FUNCTION_PASS("memcpyopt", MemCpyOptPass())
 FUNCTION_PASS("mergeicmps", MergeICmpsPass())
 FUNCTION_PASS("mergereturn", UnifyFunctionExitNodesPass())
-FUNCTION_PASS("move-auto-init", MoveAutoInitPass())
 FUNCTION_PASS("nary-reassociate", NaryReassociatePass())
 FUNCTION_PASS("newgvn", NewGVNPass())
 FUNCTION_PASS("jump-threading", JumpThreadingPass())

llvm/lib/Passes/PassRegistry.def

@@ -58,7 +58,6 @@ add_llvm_component_library(LLVMTransformUtils
   MetaRenamer.cpp
   MisExpect.cpp
   ModuleUtils.cpp
-  MoveAutoInit.cpp
   NameAnonGlobals.cpp
   PredicateInfo.cpp
   PromoteMemoryToRegister.cpp

llvm/lib/Transforms/Utils/CMakeLists.txt

@@ -206,7 +206,6 @@
 ; CHECK-O-NEXT: Running analysis: PostDominatorTreeAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: MemCpyOptPass
 ; CHECK-O23SZ-NEXT: Running pass: DSEPass
-; CHECK-O23SZ-NEXT: Running pass: MoveAutoInitPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: LoopSimplifyPass
 ; CHECK-O23SZ-NEXT: Running pass: LCSSAPass
 ; CHECK-O23SZ-NEXT: Running pass: LICMPass

llvm/lib/Transforms/Utils/MoveAutoInit.cpp

@@ -108,7 +108,6 @@
 ; CHECK-O23SZ-NEXT: Running pass: MemCpyOptPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: DSEPass on foo
 ; CHECK-O23SZ-NEXT: Running analysis: PostDominatorTreeAnalysis on foo
-; CHECK-O23SZ-NEXT: Running pass: MoveAutoInitPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: MergedLoadStoreMotionPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: LoopSimplifyPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: LCSSAPass on foo

llvm/test/Other/new-pm-defaults.ll

@@ -149,7 +149,6 @@
 ; CHECK-O-NEXT: Running analysis: PostDominatorTreeAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: MemCpyOptPass
 ; CHECK-O23SZ-NEXT: Running pass: DSEPass
-; CHECK-O23SZ-NEXT: Running pass: MoveAutoInitPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: LoopSimplifyPass
 ; CHECK-O23SZ-NEXT: Running pass: LCSSAPass
 ; CHECK-O23SZ-NEXT: Running pass: LICMPass on loop

llvm/test/Other/new-pm-lto-defaults.ll

@@ -136,7 +136,6 @@
 ; CHECK-O-NEXT: Running pass: ADCEPass
 ; CHECK-O23SZ-NEXT: Running pass: MemCpyOptPass
 ; CHECK-O23SZ-NEXT: Running pass: DSEPass
-; CHECK-O23SZ-NEXT: Running pass: MoveAutoInitPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: LoopSimplifyPass
 ; CHECK-O23SZ-NEXT: Running pass: LCSSAPass
 ; CHECK-O23SZ-NEXT: Running pass: LICMPass

llvm/test/Other/new-pm-thinlto-postlink-defaults.ll

@@ -143,7 +143,6 @@
 ; CHECK-O-NEXT: Running pass: ADCEPass
 ; CHECK-O23SZ-NEXT: Running pass: MemCpyOptPass
 ; CHECK-O23SZ-NEXT: Running pass: DSEPass
-; CHECK-O23SZ-NEXT: Running pass: MoveAutoInitPass
 ; CHECK-O23SZ-NEXT: Running pass: LoopSimplifyPass
 ; CHECK-O23SZ-NEXT: Running pass: LCSSAPass
 ; CHECK-O23SZ-NEXT: Running pass: LICMPass

llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll

@@ -147,7 +147,6 @@
 ; CHECK-O-NEXT: Running analysis: PostDominatorTreeAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: MemCpyOptPass
 ; CHECK-O23SZ-NEXT: Running pass: DSEPass
-; CHECK-O23SZ-NEXT: Running pass: MoveAutoInitPass
 ; CHECK-O23SZ-NEXT: Running pass: LoopSimplifyPass
 ; CHECK-O23SZ-NEXT: Running pass: LCSSAPass
 ; CHECK-O23SZ-NEXT: Running pass: LICMPass on loop

llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll

@@ -172,7 +172,6 @@
 ; CHECK-O-NEXT: Running pass: ADCEPass
 ; CHECK-O23SZ-NEXT: Running pass: MemCpyOptPass
 ; CHECK-O23SZ-NEXT: Running pass: DSEPass
-; CHECK-O23SZ-NEXT: Running pass: MoveAutoInitPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: LoopSimplifyPass
 ; CHECK-O23SZ-NEXT: Running pass: LCSSAPass
 ; CHECK-O23SZ-NEXT: Running pass: LICMPass

llvm/test/Other/new-pm-thinlto-prelink-defaults.ll

@@ -137,7 +137,6 @@
 ; CHECK-O-NEXT: Running pass: ADCEPass
 ; CHECK-O23SZ-NEXT: Running pass: MemCpyOptPass
 ; CHECK-O23SZ-NEXT: Running pass: DSEPass
-; CHECK-O23SZ-NEXT: Running pass: MoveAutoInitPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: LoopSimplifyPass
 ; CHECK-O23SZ-NEXT: Running pass: LCSSAPass
 ; CHECK-O23SZ-NEXT: Running pass: LICMPass