[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

(cherry picked from commit 1326a5a4cfe004181f2ec8231d84ecda2b93cb25)

4 files changed, 19 insertions, 18 deletions

diff --git a/llvm/test/Other/opt-O2-pipeline.ll b/llvm/test/Other/opt-O2-pipeline.ll
index 31527e6169b..da0edf105ee 100644
--- a/llvm/test/Other/opt-O2-pipeline.ll
+++ b/llvm/test/Other/opt-O2-pipeline.ll
@@ -100,16 +100,17 @@
 ; 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
@@ -200,13 +201,12 @@
 ; 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 cb19835e05e..113137a6fd3 100644
--- a/llvm/test/Other/opt-O3-pipeline.ll
+++ b/llvm/test/Other/opt-O3-pipeline.ll
@@ -105,16 +105,17 @@
 ; 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
@@ -205,13 +206,12 @@
 ; 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 80a74bd804e..c77f84005fe 100644
--- a/llvm/test/Other/opt-Os-pipeline.ll
+++ b/llvm/test/Other/opt-Os-pipeline.ll
@@ -87,16 +87,17 @@
 ; 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
@@ -187,13 +188,12 @@
 ; 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 6853fd9cbab..0b3b5a96060 100644
--- a/llvm/test/Other/pass-pipelines.ll
+++ b/llvm/test/Other/pass-pipelines.ll
@@ -52,6 +52,7 @@
 ; 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.