[flang] Re-enable setting noalias on procedure arguments.

[vzakhari]

This is a follow-up on #140803, which was disabled in #142128
due to #143219.

[llvmbot]

@llvm/pr-subscribers-flang-driver
@llvm/pr-subscribers-flang-openmp

@llvm/pr-subscribers-flang-fir-hlfir

Author: Slava Zakharin (vzakhari)

Changes

This is a follow-up on #140803, which was disabled in #142128
due to #143219.

---

Full diff: https://github.com/llvm/llvm-project/pull/155949.diff

1 Files Affected:

• (modified) flang/lib/Optimizer/Passes/Pipelines.cpp (+1-1)

diff --git a/flang/lib/Optimizer/Passes/Pipelines.cpp b/flang/lib/Optimizer/Passes/Pipelines.cpp
index 98f947a1f635d..6cc3290ff5cc2 100644
--- a/flang/lib/Optimizer/Passes/Pipelines.cpp
+++ b/flang/lib/Optimizer/Passes/Pipelines.cpp
@@ -14,7 +14,7 @@
 
 /// Force setting the no-alias attribute on fuction arguments when possible.
 static llvm::cl::opt<bool> forceNoAlias("force-no-alias", llvm::cl::Hidden,
-                                        llvm::cl::init(false));
+                                        llvm::cl::init(true));
 
 namespace fir {
 

[usha1830]

Looks good to me.

One suggestion: I don’t think the tests should be modified to use the flag to turn off noalias. It’s better to keep the tests using the default behavior, unless the test is specifically meant to verify the case where noalias should be avoided.

[tblah]

LGTM.

nit: I agree the tests should be updated. I don't mind doing that for you in a separate PR if you don't have time. I understand the test conflicts are only because of my revert.

[vzakhari]

I am planning removing the --force-no-alias option and updating the tests in a separate PR, if this change sticks. I would prefer keeping the test updates now: if we have to revert the option back to false, then we can just flip the switch and leave the tests as-is.

Thank you for the review and all the work you put into trying to resolve the exchange2 issues!