[TCWG CI] Regression caused by llvm: [GlobalOpt] Perform store->dominated load forwarding for stored once globals

[TCWG CI] Regression caused by llvm: [GlobalOpt] Perform store->dominated load forwarding for stored once globals

[ci_notify]

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[TCWG CI] Regression caused by llvm: [GlobalOpt] Perform store->dominated load forwarding for stored once globals:
commit 6f348b146b69a50d5fb1b9fbfd14bc1d204e45c4
Author: Arthur Eubanks <aeubanks@google.com>

    [GlobalOpt] Perform store->dominated load forwarding for stored once globals

Results regressed to
# reset_artifacts:
-10
# build_abe binutils:
-9
# build_kernel_llvm:
-5
# build_abe qemu:
-2
# linux_n_obj:
37
# First few build errors in logs:
# 00:00:51 error: include/uapi/linux/acct.h: leak CONFIG_M68K to user-space
# 00:00:51 make[1]: *** [scripts/Makefile.headersinst:63: usr/include/linux/acct.h] Error 1
# 00:00:51 make: *** [Makefile:1381: headers] Error 2

from
# reset_artifacts:
-10
# build_abe binutils:
-9
# build_kernel_llvm:
-5
# build_abe qemu:
-2
# linux_n_obj:
20742

THIS IS THE END OF INTERESTING STUFF.  BELOW ARE LINKS TO BUILDS, REPRODUCTION INSTRUCTIONS, AND THE RAW COMMIT.

This commit has regressed these CI configurations:
 - tcwg_kernel/llvm-master-arm-next-allyesconfig

First_bad build: https://ci.linaro.org/job/tcwg_kernel-llvm-bisect-llvm-master-arm-next-allyesconfig/21/artifact/artifacts/build-6f348b146b69a50d5fb1b9fbfd14bc1d204e45c4/
Last_good build: https://ci.linaro.org/job/tcwg_kernel-llvm-bisect-llvm-master-arm-next-allyesconfig/21/artifact/artifacts/build-0fe13b5f84abe1716f5991da057c801dc548a9ab/
Baseline build: https://ci.linaro.org/job/tcwg_kernel-llvm-bisect-llvm-master-arm-next-allyesconfig/21/artifact/artifacts/build-baseline/
Even more details: https://ci.linaro.org/job/tcwg_kernel-llvm-bisect-llvm-master-arm-next-allyesconfig/21/artifact/artifacts/

Reproduce builds:
<cut>
mkdir investigate-llvm-6f348b146b69a50d5fb1b9fbfd14bc1d204e45c4
cd investigate-llvm-6f348b146b69a50d5fb1b9fbfd14bc1d204e45c4

# Fetch scripts
git clone https://git.linaro.org/toolchain/jenkins-scripts

# Fetch manifests and test.sh script
mkdir -p artifacts/manifests
curl -o artifacts/manifests/build-baseline.sh https://ci.linaro.org/job/tcwg_kernel-llvm-bisect-llvm-master-arm-next-allyesconfig/21/artifact/artifacts/manifests/build-baseline.sh --fail
curl -o artifacts/manifests/build-parameters.sh https://ci.linaro.org/job/tcwg_kernel-llvm-bisect-llvm-master-arm-next-allyesconfig/21/artifact/artifacts/manifests/build-parameters.sh --fail
curl -o artifacts/test.sh https://ci.linaro.org/job/tcwg_kernel-llvm-bisect-llvm-master-arm-next-allyesconfig/21/artifact/artifacts/test.sh --fail
chmod +x artifacts/test.sh

# Reproduce the baseline build (build all pre-requisites)
./jenkins-scripts/tcwg_kernel-build.sh @@ artifacts/manifests/build-baseline.sh

# Save baseline build state (which is then restored in artifacts/test.sh)
mkdir -p ./bisect
rsync -a --del --delete-excluded --exclude /bisect/ --exclude /artifacts/ --exclude /llvm/ ./ ./bisect/baseline/

cd llvm

# Reproduce first_bad build
git checkout --detach 6f348b146b69a50d5fb1b9fbfd14bc1d204e45c4
../artifacts/test.sh

# Reproduce last_good build
git checkout --detach 0fe13b5f84abe1716f5991da057c801dc548a9ab
../artifacts/test.sh

cd ..
</cut>

Full commit (up to 1000 lines):
<cut>
commit 6f348b146b69a50d5fb1b9fbfd14bc1d204e45c4
Author: Arthur Eubanks <aeubanks@google.com>
Date:   Sat Jun 18 14:14:04 2022 -0700

    [GlobalOpt] Perform store->dominated load forwarding for stored once globals
    
    Compile time tracker:
    https://llvm-compile-time-tracker.com/compare.php?from=1e556f459b44dd0ca4073e932f66ecb6f40fe31a&to=6d7bed4e1e72c6a8592748626091274209740a40&stat=instructions
    
    Reviewed By: nikic
    
    Differential Revision: https://reviews.llvm.org/D128128
---
 llvm/lib/Transforms/IPO/GlobalOpt.cpp              | 35 ++++++++++++++++++++++
 .../GlobalOpt/malloc-promote-1-no-null-opt.ll      |  3 +-
 .../GlobalOpt/malloc-promote-2-no-null-opt.ll      |  3 +-
 llvm/test/Transforms/GlobalOpt/malloc-promote-3.ll |  3 +-
 .../GlobalOpt/shrink-global-to-bool-check-debug.ll | 13 ++++----
 .../Transforms/GlobalOpt/shrink-global-to-bool.ll  |  8 +++--
 .../GlobalOpt/stored-once-forward-value.ll         | 11 ++-----
 .../PhaseOrdering/recompute-globalsaa.ll           |  1 -
 8 files changed, 55 insertions(+), 22 deletions(-)

diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index a2b47166cdfc..6ea2242a88cb 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -1438,6 +1438,37 @@ static void makeAllConstantUsesInstructions(Constant *C) {
   }
 }
 
+// For a global variable with one store, if the store dominates any loads,
+// those loads will always load the stored value (as opposed to the
+// initializer), even in the presence of recursion.
+static bool forwardStoredOnceStore(
+    GlobalVariable *GV, const StoreInst *StoredOnceStore,
+    function_ref<DominatorTree &(Function &)> LookupDomTree) {
+  const Value *StoredOnceValue = StoredOnceStore->getValueOperand();
+  SmallVector<LoadInst *> Loads;
+  const Function *F = StoredOnceStore->getFunction();
+  for (User *U : GV->users()) {
+    if (auto *LI = dyn_cast<LoadInst>(U)) {
+      if (LI->getFunction() == F &&
+          LI->getType() == StoredOnceValue->getType() && LI->isSimple())
+        Loads.push_back(LI);
+    }
+  }
+  // Only compute DT if we have any loads to examine.
+  bool MadeChange = false;
+  if (!Loads.empty()) {
+    auto &DT = LookupDomTree(*const_cast<Function *>(F));
+    for (auto *LI : Loads) {
+      if (DT.dominates(StoredOnceStore, LI)) {
+        LI->replaceAllUsesWith(const_cast<Value *>(StoredOnceValue));
+        LI->eraseFromParent();
+        MadeChange = true;
+      }
+    }
+  }
+  return MadeChange;
+}
+
 /// Analyze the specified global variable and optimize
 /// it if possible.  If we make a change, return true.
 static bool
@@ -1597,6 +1628,10 @@ processInternalGlobal(GlobalVariable *GV, const GlobalStatus &GS,
     if (optimizeOnceStoredGlobal(GV, StoredOnceValue, DL, GetTLI))
       return true;
 
+    // Try to forward the store to any loads.
+    if (forwardStoredOnceStore(GV, GS.StoredOnceStore, LookupDomTree))
+      return true;
+
     // Otherwise, if the global was not a boolean, we can shrink it to be a
     // boolean. Skip this optimization for AS that doesn't allow an initializer.
     if (SOVConstant && GS.Ordering == AtomicOrdering::NotAtomic &&
diff --git a/llvm/test/Transforms/GlobalOpt/malloc-promote-1-no-null-opt.ll b/llvm/test/Transforms/GlobalOpt/malloc-promote-1-no-null-opt.ll
index 4cbe83766990..ccda0b8144d8 100644
--- a/llvm/test/Transforms/GlobalOpt/malloc-promote-1-no-null-opt.ll
+++ b/llvm/test/Transforms/GlobalOpt/malloc-promote-1-no-null-opt.ll
@@ -12,8 +12,7 @@ define void @init() #0 {
 ; CHECK-NEXT:    [[MALLOCCALL:%.*]] = tail call i8* @malloc(i64 4)
 ; CHECK-NEXT:    [[P:%.*]] = bitcast i8* [[MALLOCCALL]] to i32*
 ; CHECK-NEXT:    store i32* [[P]], i32** @G, align 8
-; CHECK-NEXT:    [[GV:%.*]] = load i32*, i32** @G, align 8
-; CHECK-NEXT:    store i32 0, i32* [[GV]], align 4
+; CHECK-NEXT:    store i32 0, i32* [[P]], align 4
 ; CHECK-NEXT:    ret void
 ;
   %malloccall = tail call i8* @malloc(i64 4)
diff --git a/llvm/test/Transforms/GlobalOpt/malloc-promote-2-no-null-opt.ll b/llvm/test/Transforms/GlobalOpt/malloc-promote-2-no-null-opt.ll
index 0b31aaf6a282..9c17c833a809 100644
--- a/llvm/test/Transforms/GlobalOpt/malloc-promote-2-no-null-opt.ll
+++ b/llvm/test/Transforms/GlobalOpt/malloc-promote-2-no-null-opt.ll
@@ -12,8 +12,7 @@ define void @t() #0 {
 ; CHECK-NEXT:    [[MALLOCCALL:%.*]] = tail call i8* @malloc(i64 400)
 ; CHECK-NEXT:    [[P:%.*]] = bitcast i8* [[MALLOCCALL]] to i32*
 ; CHECK-NEXT:    store i32* [[P]], i32** @G, align 8
-; CHECK-NEXT:    [[GV:%.*]] = load i32*, i32** @G, align 8
-; CHECK-NEXT:    [[GVE:%.*]] = getelementptr i32, i32* [[GV]], i32 40
+; CHECK-NEXT:    [[GVE:%.*]] = getelementptr i32, i32* [[P]], i32 40
 ; CHECK-NEXT:    store i32 20, i32* [[GVE]], align 4
 ; CHECK-NEXT:    ret void
 ;
diff --git a/llvm/test/Transforms/GlobalOpt/malloc-promote-3.ll b/llvm/test/Transforms/GlobalOpt/malloc-promote-3.ll
index fe7b4753dd5c..2a9940296c1c 100644
--- a/llvm/test/Transforms/GlobalOpt/malloc-promote-3.ll
+++ b/llvm/test/Transforms/GlobalOpt/malloc-promote-3.ll
@@ -12,8 +12,7 @@ define void @t() {
 ; CHECK-NEXT:    [[MALLOCCALL:%.*]] = tail call i8* @malloc(i64 400) #[[ATTR0:[0-9]+]]
 ; CHECK-NEXT:    [[P:%.*]] = bitcast i8* [[MALLOCCALL]] to i32*
 ; CHECK-NEXT:    store i32* [[P]], i32** @G, align 8
-; CHECK-NEXT:    [[GV:%.*]] = load i32*, i32** @G, align 8
-; CHECK-NEXT:    [[GVE:%.*]] = getelementptr i32, i32* [[GV]], i32 40
+; CHECK-NEXT:    [[GVE:%.*]] = getelementptr i32, i32* [[P]], i32 40
 ; CHECK-NEXT:    store i32 20, i32* [[GVE]], align 4
 ; CHECK-NEXT:    ret void
 ;
diff --git a/llvm/test/Transforms/GlobalOpt/shrink-global-to-bool-check-debug.ll b/llvm/test/Transforms/GlobalOpt/shrink-global-to-bool-check-debug.ll
index da396363547f..1c917413c6f0 100644
--- a/llvm/test/Transforms/GlobalOpt/shrink-global-to-bool-check-debug.ll
+++ b/llvm/test/Transforms/GlobalOpt/shrink-global-to-bool-check-debug.ll
@@ -2,21 +2,24 @@
 
 @foo = internal global i32 0, align 4
 
-define dso_local i32 @bar() {
+define void @store() {
 entry:
   store i32 5, i32* @foo, align 4
+  ret void
+}
+
+define i32 @bar() {
+entry:
   %0 = load i32, i32* @foo, align 4
   ret i32 %0
 }
 
 ;CHECK:      @bar
 ;CHECK-NEXT: entry:
-;CHECK-NEXT:   store i1 true, i1* @foo, align 1, !dbg ![[DbgLocStore:[0-9]+]]
 ;CHECK-NEXT:   %.b = load i1, i1* @foo, align 1, !dbg ![[DbgLocLoadSel:[0-9]+]]
 ;CHECK-NEXT:   %0 = select i1 %.b, i32 5, i32 0, !dbg ![[DbgLocLoadSel]]
 ;CHECK-NEXT:   call void @llvm.dbg.value({{.*}}), !dbg ![[DbgLocLoadSel]]
 ;CHECK-NEXT:   ret i32 %0, !dbg ![[DbgLocRet:[0-9]+]]
 
-;CHECK: ![[DbgLocStore]] = !DILocation(line: 1,
-;CHECK: ![[DbgLocLoadSel]] = !DILocation(line: 2,
-;CHECK: ![[DbgLocRet]] = !DILocation(line: 3,
+;CHECK: ![[DbgLocLoadSel]] = !DILocation(line: 3,
+;CHECK: ![[DbgLocRet]] = !DILocation(line: 4,
diff --git a/llvm/test/Transforms/GlobalOpt/shrink-global-to-bool.ll b/llvm/test/Transforms/GlobalOpt/shrink-global-to-bool.ll
index 74c35466992b..bdd515bf2e55 100644
--- a/llvm/test/Transforms/GlobalOpt/shrink-global-to-bool.ll
+++ b/llvm/test/Transforms/GlobalOpt/shrink-global-to-bool.ll
@@ -10,11 +10,13 @@
 ; Negative test for AS(3). Skip shrink global to bool optimization.
 ; CHECK: @lvar = internal unnamed_addr addrspace(3) global i32 undef
 
-define void @test_global_var() {
+define void @test_global_var(i1 %i) {
 ; CHECK-LABEL: @test_global_var(
 ; CHECK:    store volatile i32 10, i32* undef, align 4
 ;
 entry:
+  br i1 %i, label %bb1, label %exit
+bb1:
   store i32 10, i32* @gvar
   br label %exit
 exit:
@@ -23,13 +25,15 @@ exit:
   ret void
 }
 
-define void @test_lds_var() {
+define void @test_lds_var(i1 %i) {
 ; CHECK-LABEL: @test_lds_var(
 ; CHECK:    store i32 10, i32 addrspace(3)* @lvar, align 4
 ; CHECK:    [[LD:%.*]] = load i32, i32 addrspace(3)* @lvar, align 4
 ; CHECK:    store volatile i32 [[LD]], i32* undef, align 4
 ;
 entry:
+  br i1 %i, label %bb1, label %exit
+bb1:
   store i32 10, i32 addrspace(3)* @lvar
   br label %exit
 exit:
diff --git a/llvm/test/Transforms/GlobalOpt/stored-once-forward-value.ll b/llvm/test/Transforms/GlobalOpt/stored-once-forward-value.ll
index b043a03608a7..33a389176d15 100644
--- a/llvm/test/Transforms/GlobalOpt/stored-once-forward-value.ll
+++ b/llvm/test/Transforms/GlobalOpt/stored-once-forward-value.ll
@@ -12,10 +12,8 @@ declare void @b()
 
 define i1 @dom_const() {
 ; CHECK-LABEL: @dom_const(
-; CHECK-NEXT:    store i1 true, ptr @g1, align 1
 ; CHECK-NEXT:    call void @b()
-; CHECK-NEXT:    [[R:%.*]] = load i1, ptr @g1, align 1
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 true
 ;
   store i1 true, ptr @g1
   call void @b()
@@ -25,10 +23,8 @@ define i1 @dom_const() {
 
 define i32 @dom_arg(i32 %a) {
 ; CHECK-LABEL: @dom_arg(
-; CHECK-NEXT:    store i32 [[A:%.*]], ptr @g2, align 4
 ; CHECK-NEXT:    call void @b()
-; CHECK-NEXT:    [[R:%.*]] = load i32, ptr @g2, align 4
-; CHECK-NEXT:    ret i32 [[R]]
+; CHECK-NEXT:    ret i32 [[A:%.*]]
 ;
   store i32 %a, ptr @g2
   call void @b()
@@ -74,8 +70,7 @@ define i1 @dom_multiple_function_loads() {
 ; CHECK-LABEL: @dom_multiple_function_loads(
 ; CHECK-NEXT:    store i1 true, ptr @g5, align 1
 ; CHECK-NEXT:    call void @b()
-; CHECK-NEXT:    [[R:%.*]] = load i1, ptr @g5, align 1
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 true
 ;
   store i1 true, ptr @g5
   call void @b()
diff --git a/llvm/test/Transforms/PhaseOrdering/recompute-globalsaa.ll b/llvm/test/Transforms/PhaseOrdering/recompute-globalsaa.ll
index 3dbddbdb96fa..f4290c64a773 100644
--- a/llvm/test/Transforms/PhaseOrdering/recompute-globalsaa.ll
+++ b/llvm/test/Transforms/PhaseOrdering/recompute-globalsaa.ll
@@ -9,7 +9,6 @@
 define i32 @main() {
 ; CHECK-LABEL: @main(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    store i1 true, i1* @a, align 4
 ; CHECK-NEXT:    [[TMP0:%.*]] = load i32*, i32** @e, align 8
 ; CHECK-NEXT:    store i32 0, i32* [[TMP0]], align 4
 ; CHECK-NEXT:    store i32* null, i32** @e, align 8
</cut>

Re: [TCWG CI] Regression caused by llvm: [GlobalOpt] Perform store->dominated load forwarding for stored once globals

[Nathan Chancellor]

On Mon, Jun 20, 2022 at 04:50:08PM +0000, ci_notify@linaro.org wrote:
> [TCWG CI] Regression caused by llvm: [GlobalOpt] Perform store->dominated load forwarding for stored once globals:
> commit 6f348b146b69a50d5fb1b9fbfd14bc1d204e45c4
> Author: Arthur Eubanks <aeubanks@google.com>
> 
>     [GlobalOpt] Perform store->dominated load forwarding for stored once globals
> 
> Results regressed to
> # reset_artifacts:
> -10
> # build_abe binutils:
> -9
> # build_kernel_llvm:
> -5
> # build_abe qemu:
> -2
> # linux_n_obj:
> 37
> # First few build errors in logs:
> # 00:00:51 error: include/uapi/linux/acct.h: leak CONFIG_M68K to user-space
> # 00:00:51 make[1]: *** [scripts/Makefile.headersinst:63: usr/include/linux/acct.h] Error 1
> # 00:00:51 make: *** [Makefile:1381: headers] Error 2

I know this change was reverted already (13ff7d6f393d) but I think the
only way this change could be responsible for this error is through a
miscompile of scripts/unifdef.c, as scripts/headers_install.sh relies on
that tool to strip away !__KERNEL__ sections. I can try to reduce
something out if necessary.

Cheers,
Nathan