[DSE] Enable the initializes improvement in DSE

[haopliu]

(Retry) enable the initializes improvement in DSE.

Initially enabled in #119116.

Fix the aliasing issue through global variables in #120044.

The compile-time comparison of this enabling (no meaningful diff): https://llvm-compile-time-tracker.com/compare.php?from=b46fcb9fa32f24660b1b8858d5c4cbdb76ef9d8b&to=33dc817b81f7898c87b052d1ddfd3d6e6f5b5dbd&stat=instructions%3Au

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: Haopeng Liu (haopliu)

Changes

(Retry) enable the initializes improvement in DSE.

Initially enabled in #119116.

Fix the aliasing issue through global variables in #120044.

The compile-time comparison of this enabling (no meaningful diff): https://llvm-compile-time-tracker.com/compare.php?from=b46fcb9fa32f24660b1b8858d5c4cbdb76ef9d8b&to=33dc817b81f7898c87b052d1ddfd3d6e6f5b5dbd&stat=instructions%3Au

---

Full diff: https://github.com/llvm/llvm-project/pull/124058.diff

1 Files Affected:

• (modified) llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp (+2-2)

diff --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
index 241c57e88b447e..de15748ff06374 100644
--- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -164,9 +164,9 @@ static cl::opt<bool>
     OptimizeMemorySSA("dse-optimize-memoryssa", cl::init(true), cl::Hidden,
                       cl::desc("Allow DSE to optimize memory accesses."));
 
-// TODO: turn on and remove this flag.
+// TODO: remove this flag.
 static cl::opt<bool> EnableInitializesImprovement(
-    "enable-dse-initializes-attr-improvement", cl::init(false), cl::Hidden,
+    "enable-dse-initializes-attr-improvement", cl::init(true), cl::Hidden,
     cl::desc("Enable the initializes attr improvement in DSE"));
 
 //===----------------------------------------------------------------------===//

[nikic]

LGTM

[fhahn]

Very excited to get this enabled, thanks for working on this!