[PATCH] D59564: [LICM & MemorySSA] Don't sink/hoist stores in the presence of ordered loads.
Alina Sbirlea via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Wed Mar 20 10:20:46 PDT 2019
asbirlea updated this revision to Diff 191526.
asbirlea marked 5 inline comments as done.
asbirlea added a comment.
Address comments.
Repository:
rL LLVM
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D59564/new/
https://reviews.llvm.org/D59564
Files:
lib/Transforms/Scalar/LICM.cpp
test/Transforms/LICM/hoist-debuginvariant.ll
Index: test/Transforms/LICM/hoist-debuginvariant.ll
===================================================================
--- test/Transforms/LICM/hoist-debuginvariant.ll
+++ test/Transforms/LICM/hoist-debuginvariant.ll
@@ -1,6 +1,6 @@
; RUN: opt < %s -licm -S | FileCheck %s
; RUN: opt < %s -strip-debug -licm -S | FileCheck %s
-; RUN: opt < %s -licm -enable-mssa-loop-dependency=true -verify-memoryssa -S | FileCheck %s --check-prefixes=CHECK,MSSA
+; RUN: opt < %s -licm -enable-mssa-loop-dependency=true -verify-memoryssa -S | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
@@ -17,7 +17,6 @@
; CHECK-NEXT: [[_TMP2:%.*]] = load i32, i32* @a, align 4
; CHECK-NEXT: [[_TMP3:%.*]] = load i32, i32* @b, align 4
; CHECK-NEXT: [[_TMP4:%.*]] = sdiv i32 [[_TMP2]], [[_TMP3]]
-; MSSA-NEXT: store i32 [[_TMP4:%.*]], i32* @c, align 4
; CHECK-NEXT: br label [[BB3:%.*]]
br label %bb3
Index: lib/Transforms/Scalar/LICM.cpp
===================================================================
--- lib/Transforms/Scalar/LICM.cpp
+++ lib/Transforms/Scalar/LICM.cpp
@@ -1191,33 +1191,37 @@
} else { // MSSAU
if (isOnlyMemoryAccess(SI, CurLoop, MSSAU))
return true;
- if (*LicmMssaOptCounter < LicmMssaOptCap) {
+ // If there are more accesses than the Promotion cap, give up, we're not
+ // walking a list that long.
+ if (NoOfMemAccTooLarge)
+ return false;
+ // Check store only if there's still "quota" to check clobber.
+ if (*LicmMssaOptCounter >= LicmMssaOptCap)
+ return false;
+ // If there are interfering Uses (i.e. their defining access is in the
+ // loop), or ordered loads (stored as Defs!), don't move this store.
+ // Could do better here, but this is conservatively correct.
+ // TODO: Cache set of Uses on the first walk in runOnLoop, update when
+ // moving accesses. Can also extend to dominating uses.
+ for (auto *BB : CurLoop->getBlocks())
+ if (auto *Accesses = MSSA->getBlockAccesses(BB))
+ for (const auto &MA : *Accesses)
+ if (const auto *MU = dyn_cast<MemoryUse>(&MA)) {
+ auto *MD = MU->getDefiningAccess();
+ if (!MSSA->isLiveOnEntryDef(MD) &&
+ CurLoop->contains(MD->getBlock()))
+ return false;
+ } else if (const auto *MD = dyn_cast<MemoryDef>(&MA))
+ if (auto *LI = dyn_cast<LoadInst>(MD->getMemoryInst())) {
+ assert(!LI->isUnordered() && "Expected unordered load");
+ return false;
+ }
+
auto *Source = MSSA->getSkipSelfWalker()->getClobberingMemoryAccess(SI);
(*LicmMssaOptCounter)++;
- // If there are no clobbering Defs in the loop, we still need to check
- // for interfering Uses. If there are more accesses than the Promotion
- // cap, give up, we're not walking a list that long. Otherwise, walk the
- // list, check each Use if it's optimized to an access outside the loop.
- // If yes, store is safe to hoist. This is fairly restrictive, but
- // conservatively correct.
- // TODO: Cache set of Uses on the first walk in runOnLoop, update when
- // moving accesses. Can also extend to dominating uses.
- if ((!MSSA->isLiveOnEntryDef(Source) &&
- CurLoop->contains(Source->getBlock())) ||
- NoOfMemAccTooLarge)
- return false;
- for (auto *BB : CurLoop->getBlocks())
- if (auto *Accesses = MSSA->getBlockAccesses(BB))
- for (const auto &MA : *Accesses)
- if (const auto *MU = dyn_cast<MemoryUse>(&MA)) {
- auto *MD = MU->getDefiningAccess();
- if (!MSSA->isLiveOnEntryDef(MD) &&
- CurLoop->contains(MD->getBlock()))
- return false;
- }
- return true;
- }
- return false;
+ // If there are no clobbering Defs in the loop, store is safe to hoist.
+ return MSSA->isLiveOnEntryDef(Source) ||
+ !CurLoop->contains(Source->getBlock())
}
}
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