[llvm-branch-commits] [clang] [flang] release/21.x: [flang] Disable loop interchange by default (#155279) (PR #155362)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/155362

Backport 8849750e998819903dc749411bc9a7cd508a5e8a

Requested by: @nikic

>From 154a89dabad4f306bd1774b43eafbae882733bb0 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Tue, 26 Aug 2025 09:14:21 +0200
Subject: [PATCH] [flang] Disable loop interchange by default (#155279)

Disable loop interchange by default, while keeping the ability to
explicitly enable using `-floop-interchange`. This matches Clang.

See discussion on https://github.com/llvm/llvm-project/pull/140182.

(cherry picked from commit 8849750e998819903dc749411bc9a7cd508a5e8a)
---
 clang/lib/Driver/ToolChains/CommonArgs.cpp | 10 ++--------
 flang/test/Driver/loop-interchange.f90     |  6 +++---
 2 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 3086c14fdaa4a..8d3775de9be5e 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -3265,14 +3265,8 @@ void tools::handleVectorizeSLPArgs(const ArgList &Args,
 
 void tools::handleInterchangeLoopsArgs(const ArgList &Args,
                                        ArgStringList &CmdArgs) {
-  // FIXME: instead of relying on shouldEnableVectorizerAtOLevel, we may want to
-  // implement a separate function to infer loop interchange from opt level.
-  // For now, enable loop-interchange at the same opt levels as loop-vectorize.
-  bool EnableInterchange = shouldEnableVectorizerAtOLevel(Args, false);
-  OptSpecifier InterchangeAliasOption =
-      EnableInterchange ? options::OPT_O_Group : options::OPT_floop_interchange;
-  if (Args.hasFlag(options::OPT_floop_interchange, InterchangeAliasOption,
-                   options::OPT_fno_loop_interchange, EnableInterchange))
+  if (Args.hasFlag(options::OPT_floop_interchange,
+                   options::OPT_fno_loop_interchange, false))
     CmdArgs.push_back("-floop-interchange");
 }
 
diff --git a/flang/test/Driver/loop-interchange.f90 b/flang/test/Driver/loop-interchange.f90
index 5d3ec71c59874..1e5a11902709c 100644
--- a/flang/test/Driver/loop-interchange.f90
+++ b/flang/test/Driver/loop-interchange.f90
@@ -2,9 +2,9 @@
 ! RUN: %flang -### -S -fno-loop-interchange %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s
 ! RUN: %flang -### -S -O0 %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s
 ! RUN: %flang -### -S -O1 %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s
-! RUN: %flang -### -S -O2 %s 2>&1 | FileCheck -check-prefix=CHECK-LOOP-INTERCHANGE %s
-! RUN: %flang -### -S -O3 %s 2>&1 | FileCheck -check-prefix=CHECK-LOOP-INTERCHANGE %s
-! RUN: %flang -### -S -Os %s 2>&1 | FileCheck -check-prefix=CHECK-LOOP-INTERCHANGE %s
+! RUN: %flang -### -S -O2 %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s
+! RUN: %flang -### -S -O3 %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s
+! RUN: %flang -### -S -Os %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s
 ! RUN: %flang -### -S -Oz %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s
 ! CHECK-LOOP-INTERCHANGE: "-floop-interchange"
 ! CHECK-NO-LOOP-INTERCHANGE-NOT: "-floop-interchange"