[LoopRotate] Get and update MSSA only if available in legacy pass manager.

Summary:
Potential fix for: https://bugs.llvm.org/show_bug.cgi?id=44889 and https://bugs.llvm.org/show_bug.cgi?id=44408

In the legacy pass manager, loop rotate need not compute MemorySSA when not being in the same loop pass manager with other loop passes.
There isn't currently a way to differentiate between the two cases, so this attempts to limit the usage in LoopRotate to only update MemorySSA when the analysis is already available.
The side-effect of this is that it will split the Loop pipeline.

This issue does not apply to the new pass manager, where we have a flag specifying if all loop passes in that loop pass manager preserve MemorySSA.

Reviewers: dmgreen, fedor.sergeev, nikic

Subscribers: Prazek, hiraditya, george.burgess.iv, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74574

diff --git a/llvm/lib/Transforms/Scalar/LoopRotation.cpp b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
index ed38169..f92566b 100644 (file)
--- a/llvm/lib/Transforms/Scalar/LoopRotation.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
@@ -81,10 +81,8 @@ public:
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.addRequired<AssumptionCacheTracker>();
     AU.addRequired<TargetTransformInfoWrapperPass>();
-    if (EnableMSSALoopDependency) {
-      AU.addRequired<MemorySSAWrapperPass>();
+    if (EnableMSSALoopDependency)
       AU.addPreserved<MemorySSAWrapperPass>();
-    }
     getLoopAnalysisUsage(AU);
   }
 
@@ -101,8 +99,11 @@ public:
     const SimplifyQuery SQ = getBestSimplifyQuery(*this, F);
     Optional<MemorySSAUpdater> MSSAU;
     if (EnableMSSALoopDependency) {
-      MemorySSA *MSSA = &getAnalysis<MemorySSAWrapperPass>().getMSSA();
-      MSSAU = MemorySSAUpdater(MSSA);
+      // Not requiring MemorySSA and getting it only if available will split
+      // the loop pass pipeline when LoopRotate is being run first.
+      auto *MSSAA = getAnalysisIfAvailable<MemorySSAWrapperPass>();
+      if (MSSAA)
+        MSSAU = MemorySSAUpdater(&MSSAA->getMSSA());
     }
     return LoopRotation(L, LI, TTI, AC, &DT, &SE,
                         MSSAU.hasValue() ? MSSAU.getPointer() : nullptr, SQ,

diff --git a/llvm/test/Other/opt-O2-pipeline.ll b/llvm/test/Other/opt-O2-pipeline.ll
index 49144be..28137f6 100644 (file)
--- a/llvm/test/Other/opt-O2-pipeline.ll
+++ b/llvm/test/Other/opt-O2-pipeline.ll
@@ -101,16 +101,17 @@
 ; CHECK-NEXT:         Simplify the CFG
 ; CHECK-NEXT:         Reassociate expressions
 ; CHECK-NEXT:         Dominator Tree Construction
-; CHECK-NEXT:         Basic Alias Analysis (stateless AA impl)
-; CHECK-NEXT:         Function Alias Analysis Results
-; CHECK-NEXT:         Memory SSA
 ; CHECK-NEXT:         Natural Loop Information
 ; CHECK-NEXT:         Canonicalize natural loops
 ; CHECK-NEXT:         LCSSA Verifier
 ; CHECK-NEXT:         Loop-Closed SSA Form Pass
+; CHECK-NEXT:         Basic Alias Analysis (stateless AA impl)
+; CHECK-NEXT:         Function Alias Analysis Results
 ; CHECK-NEXT:         Scalar Evolution Analysis
 ; CHECK-NEXT:         Loop Pass Manager
 ; CHECK-NEXT:           Rotate Loops
+; CHECK-NEXT:         Memory SSA
+; CHECK-NEXT:         Loop Pass Manager
 ; CHECK-NEXT:           Loop Invariant Code Motion
 ; CHECK-NEXT:           Unswitch loops
 ; CHECK-NEXT:         Simplify the CFG
@@ -198,13 +199,12 @@
 ; CHECK-NEXT:       Float to int
 ; CHECK-NEXT:       Lower constant intrinsics
 ; CHECK-NEXT:       Dominator Tree Construction
-; CHECK-NEXT:       Basic Alias Analysis (stateless AA impl)
-; CHECK-NEXT:       Function Alias Analysis Results
-; CHECK-NEXT:       Memory SSA
 ; CHECK-NEXT:       Natural Loop Information
 ; CHECK-NEXT:       Canonicalize natural loops
 ; CHECK-NEXT:       LCSSA Verifier
 ; CHECK-NEXT:       Loop-Closed SSA Form Pass
+; CHECK-NEXT:       Basic Alias Analysis (stateless AA impl)
+; CHECK-NEXT:       Function Alias Analysis Results
 ; CHECK-NEXT:       Scalar Evolution Analysis
 ; CHECK-NEXT:       Loop Pass Manager
 ; CHECK-NEXT:         Rotate Loops

diff --git a/llvm/test/Other/opt-O3-pipeline.ll b/llvm/test/Other/opt-O3-pipeline.ll
index cbb90ee..61b5b9c 100644 (file)
--- a/llvm/test/Other/opt-O3-pipeline.ll
+++ b/llvm/test/Other/opt-O3-pipeline.ll
@@ -106,16 +106,17 @@
 ; CHECK-NEXT:         Simplify the CFG
 ; CHECK-NEXT:         Reassociate expressions
 ; CHECK-NEXT:         Dominator Tree Construction
-; CHECK-NEXT:         Basic Alias Analysis (stateless AA impl)
-; CHECK-NEXT:         Function Alias Analysis Results
-; CHECK-NEXT:         Memory SSA
 ; CHECK-NEXT:         Natural Loop Information
 ; CHECK-NEXT:         Canonicalize natural loops
 ; CHECK-NEXT:         LCSSA Verifier
 ; CHECK-NEXT:         Loop-Closed SSA Form Pass
+; CHECK-NEXT:         Basic Alias Analysis (stateless AA impl)
+; CHECK-NEXT:         Function Alias Analysis Results
 ; CHECK-NEXT:         Scalar Evolution Analysis
 ; CHECK-NEXT:         Loop Pass Manager
 ; CHECK-NEXT:           Rotate Loops
+; CHECK-NEXT:         Memory SSA
+; CHECK-NEXT:         Loop Pass Manager
 ; CHECK-NEXT:           Loop Invariant Code Motion
 ; CHECK-NEXT:           Unswitch loops
 ; CHECK-NEXT:         Simplify the CFG
@@ -203,13 +204,12 @@
 ; CHECK-NEXT:       Float to int
 ; CHECK-NEXT:       Lower constant intrinsics
 ; CHECK-NEXT:       Dominator Tree Construction
-; CHECK-NEXT:       Basic Alias Analysis (stateless AA impl)
-; CHECK-NEXT:       Function Alias Analysis Results
-; CHECK-NEXT:       Memory SSA
 ; CHECK-NEXT:       Natural Loop Information
 ; CHECK-NEXT:       Canonicalize natural loops
 ; CHECK-NEXT:       LCSSA Verifier
 ; CHECK-NEXT:       Loop-Closed SSA Form Pass
+; CHECK-NEXT:       Basic Alias Analysis (stateless AA impl)
+; CHECK-NEXT:       Function Alias Analysis Results
 ; CHECK-NEXT:       Scalar Evolution Analysis
 ; CHECK-NEXT:       Loop Pass Manager
 ; CHECK-NEXT:         Rotate Loops

diff --git a/llvm/test/Other/opt-Os-pipeline.ll b/llvm/test/Other/opt-Os-pipeline.ll
index ce38013..81f82d0 100644 (file)
--- a/llvm/test/Other/opt-Os-pipeline.ll
+++ b/llvm/test/Other/opt-Os-pipeline.ll
@@ -88,16 +88,17 @@
 ; CHECK-NEXT:         Simplify the CFG
 ; CHECK-NEXT:         Reassociate expressions
 ; CHECK-NEXT:         Dominator Tree Construction
-; CHECK-NEXT:         Basic Alias Analysis (stateless AA impl)
-; CHECK-NEXT:         Function Alias Analysis Results
-; CHECK-NEXT:         Memory SSA
 ; CHECK-NEXT:         Natural Loop Information
 ; CHECK-NEXT:         Canonicalize natural loops
 ; CHECK-NEXT:         LCSSA Verifier
 ; CHECK-NEXT:         Loop-Closed SSA Form Pass
+; CHECK-NEXT:         Basic Alias Analysis (stateless AA impl)
+; CHECK-NEXT:         Function Alias Analysis Results
 ; CHECK-NEXT:         Scalar Evolution Analysis
 ; CHECK-NEXT:         Loop Pass Manager
 ; CHECK-NEXT:           Rotate Loops
+; CHECK-NEXT:         Memory SSA
+; CHECK-NEXT:         Loop Pass Manager
 ; CHECK-NEXT:           Loop Invariant Code Motion
 ; CHECK-NEXT:           Unswitch loops
 ; CHECK-NEXT:         Simplify the CFG
@@ -185,13 +186,12 @@
 ; CHECK-NEXT:       Float to int
 ; CHECK-NEXT:       Lower constant intrinsics
 ; CHECK-NEXT:       Dominator Tree Construction
-; CHECK-NEXT:       Basic Alias Analysis (stateless AA impl)
-; CHECK-NEXT:       Function Alias Analysis Results
-; CHECK-NEXT:       Memory SSA
 ; CHECK-NEXT:       Natural Loop Information
 ; CHECK-NEXT:       Canonicalize natural loops
 ; CHECK-NEXT:       LCSSA Verifier
 ; CHECK-NEXT:       Loop-Closed SSA Form Pass
+; CHECK-NEXT:       Basic Alias Analysis (stateless AA impl)
+; CHECK-NEXT:       Function Alias Analysis Results
 ; CHECK-NEXT:       Scalar Evolution Analysis
 ; CHECK-NEXT:       Loop Pass Manager
 ; CHECK-NEXT:         Rotate Loops

diff --git a/llvm/test/Other/pass-pipelines.ll b/llvm/test/Other/pass-pipelines.ll
index b3887cf..718ca46 100644 (file)
--- a/llvm/test/Other/pass-pipelines.ll
+++ b/llvm/test/Other/pass-pipelines.ll
@@ -54,6 +54,7 @@
 ; CHECK-O2-NEXT: FunctionPass Manager
 ; CHECK-O2-NOT: Manager
 ; CHECK-O2: Loop Pass Manager
+; CHECK-O2: Loop Pass Manager
 ; CHECK-O2-NOT: Manager
 ; FIXME: We shouldn't be pulling out to simplify-cfg and instcombine and
 ; causing new loop pass managers.