[llvm-branch-commits] [llvm] 1518865 - Revert "[SimplifyCFG] Avoid threading for loop headers (#151142)"
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Tue Aug 26 18:02:25 PDT 2025
Author: Alexander Kornienko
Date: 2025-08-27T03:02:22+02:00
New Revision: 151886507b93d3f3888d59d512ad9048426579ea
URL: https://github.com/llvm/llvm-project/commit/151886507b93d3f3888d59d512ad9048426579ea
DIFF: https://github.com/llvm/llvm-project/commit/151886507b93d3f3888d59d512ad9048426579ea.diff
LOG: Revert "[SimplifyCFG] Avoid threading for loop headers (#151142)"
This reverts commit ea2f5395b1acdc6eaf69a79b7660d7fa7d08c271.
Added:
Modified:
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/test/CodeGen/ARM/2013-05-05-IfConvertBug.ll
llvm/test/Transforms/SimplifyCFG/2008-07-13-InfLoopMiscompile.ll
llvm/test/Transforms/SimplifyCFG/branch-phi-thread.ll
llvm/test/Transforms/SimplifyCFG/jump-threading.ll
llvm/test/Transforms/SimplifyCFG/two-entry-phi-return.ll
Removed:
llvm/test/Transforms/SimplifyCFG/2025-07-29-non-canoncial-loop.ll
################################################################################
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index ef110a6922f05..6290423f032b3 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -291,7 +291,6 @@ class SimplifyCFGOpt {
bool simplifyBranch(BranchInst *Branch, IRBuilder<> &Builder);
bool simplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder);
bool simplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder);
- bool foldCondBranchOnValueKnownInPredecessor(BranchInst *BI);
bool tryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI,
IRBuilder<> &Builder);
@@ -3690,19 +3689,15 @@ foldCondBranchOnValueKnownInPredecessorImpl(BranchInst *BI, DomTreeUpdater *DTU,
return false;
}
-bool SimplifyCFGOpt::foldCondBranchOnValueKnownInPredecessor(BranchInst *BI) {
- // Note: If BB is a loop header then there is a risk that threading introduces
- // a non-canonical loop by moving a back edge. So we avoid this optimization
- // for loop headers if NeedCanonicalLoop is set.
- if (Options.NeedCanonicalLoop && is_contained(LoopHeaders, BI->getParent()))
- return false;
-
+static bool foldCondBranchOnValueKnownInPredecessor(BranchInst *BI,
+ DomTreeUpdater *DTU,
+ const DataLayout &DL,
+ AssumptionCache *AC) {
std::optional<bool> Result;
bool EverChanged = false;
do {
// Note that None means "we changed things, but recurse further."
- Result =
- foldCondBranchOnValueKnownInPredecessorImpl(BI, DTU, DL, Options.AC);
+ Result = foldCondBranchOnValueKnownInPredecessorImpl(BI, DTU, DL, AC);
EverChanged |= Result == std::nullopt || *Result;
} while (Result == std::nullopt);
return EverChanged;
@@ -8123,7 +8118,7 @@ bool SimplifyCFGOpt::simplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
// If this is a branch on something for which we know the constant value in
// predecessors (e.g. a phi node in the current block), thread control
// through this block.
- if (foldCondBranchOnValueKnownInPredecessor(BI))
+ if (foldCondBranchOnValueKnownInPredecessor(BI, DTU, DL, Options.AC))
return requestResimplify();
// Scan predecessor blocks for conditional branches.
diff --git a/llvm/test/CodeGen/ARM/2013-05-05-IfConvertBug.ll b/llvm/test/CodeGen/ARM/2013-05-05-IfConvertBug.ll
index 8f798fac06f54..344bb15d2a8b8 100644
--- a/llvm/test/CodeGen/ARM/2013-05-05-IfConvertBug.ll
+++ b/llvm/test/CodeGen/ARM/2013-05-05-IfConvertBug.ll
@@ -1,7 +1,7 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc -keep-loops="false" < %s -mtriple=thumbv7-apple-ios -mcpu=cortex-a8 | FileCheck %s
-; RUN: llc -keep-loops="false" < %s -mtriple=thumbv8 | FileCheck -check-prefix=CHECK-V8 %s
-; RUN: llc -keep-loops="false" < %s -mtriple=thumbv7 -arm-restrict-it | FileCheck -check-prefix=CHECK-RESTRICT-IT %s
+; RUN: llc < %s -mtriple=thumbv7-apple-ios -mcpu=cortex-a8 | FileCheck %s
+; RUN: llc < %s -mtriple=thumbv8 | FileCheck -check-prefix=CHECK-V8 %s
+; RUN: llc < %s -mtriple=thumbv7 -arm-restrict-it | FileCheck -check-prefix=CHECK-RESTRICT-IT %s
define i32 @t1(i32 %a, i32 %b, ptr %retaddr) {
; CHECK-LABEL: t1:
diff --git a/llvm/test/Transforms/SimplifyCFG/2008-07-13-InfLoopMiscompile.ll b/llvm/test/Transforms/SimplifyCFG/2008-07-13-InfLoopMiscompile.ll
index 44d92e1a1c210..2e9e7b19c73e2 100644
--- a/llvm/test/Transforms/SimplifyCFG/2008-07-13-InfLoopMiscompile.ll
+++ b/llvm/test/Transforms/SimplifyCFG/2008-07-13-InfLoopMiscompile.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -passes=simplifycfg -simplifycfg-require-and-preserve-domtree=1 -keep-loops="false" -S | FileCheck %s
+; RUN: opt < %s -passes=simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s
; PR2540
; Outval should end up with a select from 0/2, not all constants.
@@ -52,3 +52,4 @@ func_1.exit: ; preds = %cowblock, %entry
}
declare i32 @printf(ptr, ...) nounwind
+
diff --git a/llvm/test/Transforms/SimplifyCFG/2025-07-29-non-canoncial-loop.ll b/llvm/test/Transforms/SimplifyCFG/2025-07-29-non-canoncial-loop.ll
deleted file mode 100644
index 322dd98f48df1..0000000000000
--- a/llvm/test/Transforms/SimplifyCFG/2025-07-29-non-canoncial-loop.ll
+++ /dev/null
@@ -1,62 +0,0 @@
-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
-; RUN: opt < %s -passes=simplifycfg -simplifycfg-require-and-preserve-domtree=1 --keep-loops="true" -S | FileCheck --check-prefix=NO-THREADING %s
-; Checks that we do not thread the control flow through the loop header loop_header as
-; that will introduce a non-canonical loop.
-
-; RUN: opt < %s -passes=simplifycfg -simplifycfg-require-and-preserve-domtree=1 --keep-loops="false" -S | FileCheck --check-prefix=THREADING %s
-; Checks that we thread the control flow through the loop header loop_header since we
-; do not request --keep-loops.
-
-define void @__start(i1 %cond) {
-; NO-THREADING-LABEL: define void @__start(
-; NO-THREADING-SAME: i1 [[COND:%.*]]) {
-; NO-THREADING-NEXT: [[ENTRY:.*:]]
-; NO-THREADING-NEXT: br label %[[LOOP_HEADER:.*]]
-; NO-THREADING: [[LOOP_HEADER]]:
-; NO-THREADING-NEXT: br i1 [[COND]], label %[[LOOP_BODY_1:.*]], label %[[LOOP_BODY_0:.*]]
-; NO-THREADING: [[LOOP_BODY_0]]:
-; NO-THREADING-NEXT: [[_0_:%.*]] = add i16 0, 0
-; NO-THREADING-NEXT: br label %[[LOOP_EXIT:.*]]
-; NO-THREADING: [[LOOP_BODY_1]]:
-; NO-THREADING-NEXT: [[_1_:%.*]] = add i32 0, 1
-; NO-THREADING-NEXT: br label %[[LOOP_EXIT]]
-; NO-THREADING: [[LOOP_EXIT]]:
-; NO-THREADING-NEXT: br i1 [[COND]], label %[[LOOP_HEADER]], label %[[EXIT:.*]]
-; NO-THREADING: [[EXIT]]:
-; NO-THREADING-NEXT: ret void
-;
-; THREADING-LABEL: define void @__start(
-; THREADING-SAME: i1 [[COND:%.*]]) {
-; THREADING-NEXT: [[ENTRY:.*:]]
-; THREADING-NEXT: br i1 [[COND]], label %[[LOOP_BODY_1:.*]], label %[[LOOP_BODY_0:.*]]
-; THREADING: [[LOOP_BODY_0]]:
-; THREADING-NEXT: [[_0_:%.*]] = add i16 0, 0
-; THREADING-NEXT: br label %[[LOOP_EXIT:.*]]
-; THREADING: [[LOOP_BODY_1]]:
-; THREADING-NEXT: [[_1_:%.*]] = add i32 0, 1
-; THREADING-NEXT: br label %[[LOOP_EXIT]]
-; THREADING: [[LOOP_EXIT]]:
-; THREADING-NEXT: br i1 [[COND]], label %[[LOOP_BODY_1]], label %[[EXIT:.*]]
-; THREADING: [[EXIT]]:
-; THREADING-NEXT: ret void
-;
-entry:
- br label %loop_header
-
-loop_header: ; preds = %loop_exit, %entry
- br i1 %cond, label %loop_body_1, label %loop_body_0
-
-loop_body_0: ; preds = %loop_header
- %_0_ = add i16 0, 0
- br label %loop_exit
-
-loop_body_1: ; preds = %loop_header
- %_1_ = add i32 0, 1
- br label %loop_exit
-
-loop_exit: ; preds = %loop_body_1, %loop_body_0
- br i1 %cond, label %loop_header, label %exit
-
-exit: ; preds = %loop_exit
- ret void
-}
diff --git a/llvm/test/Transforms/SimplifyCFG/branch-phi-thread.ll b/llvm/test/Transforms/SimplifyCFG/branch-phi-thread.ll
index ec9423bd81675..0afec05ecbd6a 100644
--- a/llvm/test/Transforms/SimplifyCFG/branch-phi-thread.ll
+++ b/llvm/test/Transforms/SimplifyCFG/branch-phi-thread.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -passes=simplifycfg,adce -simplifycfg-require-and-preserve-domtree=1 -keep-loops="false" -S | FileCheck %s
+; RUN: opt < %s -passes=simplifycfg,adce -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s
declare void @f1()
diff --git a/llvm/test/Transforms/SimplifyCFG/jump-threading.ll b/llvm/test/Transforms/SimplifyCFG/jump-threading.ll
index a4073ae6eb0b4..50a32413a0551 100644
--- a/llvm/test/Transforms/SimplifyCFG/jump-threading.ll
+++ b/llvm/test/Transforms/SimplifyCFG/jump-threading.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -S -passes=simplifycfg -keep-loops="false" < %s | FileCheck %s
+; RUN: opt -S -passes=simplifycfg < %s | FileCheck %s
declare void @foo()
declare void @bar()
diff --git a/llvm/test/Transforms/SimplifyCFG/two-entry-phi-return.ll b/llvm/test/Transforms/SimplifyCFG/two-entry-phi-return.ll
index f6d71ddda74fe..57930c91b9796 100644
--- a/llvm/test/Transforms/SimplifyCFG/two-entry-phi-return.ll
+++ b/llvm/test/Transforms/SimplifyCFG/two-entry-phi-return.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -passes=simplifycfg -simplifycfg-require-and-preserve-domtree=1 -keep-loops="false" -S | FileCheck %s
+; RUN: opt < %s -passes=simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s
define i1 @qux(ptr %m, ptr %n, ptr %o, ptr %p) nounwind {
; CHECK-LABEL: @qux(
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