[llvm] 1ed7f8e - [LAA] Support pointer phis in loop by analyzing each incoming pointer.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Wed Apr 28 12:20:15 PDT 2021
Author: Florian Hahn
Date: 2021-04-28T20:19:40+01:00
New Revision: 1ed7f8ede564c3b11da4fdca30c36ccbff422576
URL: https://github.com/llvm/llvm-project/commit/1ed7f8ede564c3b11da4fdca30c36ccbff422576
DIFF: https://github.com/llvm/llvm-project/commit/1ed7f8ede564c3b11da4fdca30c36ccbff422576.diff
LOG: [LAA] Support pointer phis in loop by analyzing each incoming pointer.
SCEV does not look through non-header PHIs inside the loop. Such phis
can be analyzed by adding separate accesses for each incoming pointer
value.
This results in 2 more loops vectorized in SPEC2000/186.crafty and
avoids regressions when sinking instructions before vectorizing.
Reviewed By: Meinersbur
Differential Revision: https://reviews.llvm.org/D101286
Added:
Modified:
llvm/lib/Analysis/LoopAccessAnalysis.cpp
llvm/test/Analysis/LoopAccessAnalysis/pointer-phis.ll
llvm/test/Transforms/LoopVectorize/vectorize-pointer-phis.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 2a6987848ca59..cd086328ec682 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -1938,7 +1938,18 @@ void LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
if (blockNeedsPredication(ST->getParent(), TheLoop, DT))
Loc.AATags.TBAA = nullptr;
- Accesses.addStore(Loc);
+ // SCEV does not look through non-header PHIs inside the loop. Such phis
+ // can be analyzed by adding separate accesses for each incoming pointer
+ // value.
+ auto *PN = dyn_cast<PHINode>(Loc.Ptr);
+ if (PN && TheLoop->contains(PN->getParent()) &&
+ PN->getParent() != TheLoop->getHeader()) {
+ for (const Use &Inc : PN->incoming_values()) {
+ MemoryLocation NewLoc = Loc.getWithNewPtr(Inc);
+ Accesses.addStore(NewLoc);
+ }
+ } else
+ Accesses.addStore(Loc);
}
}
@@ -1982,7 +1993,17 @@ void LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
if (blockNeedsPredication(LD->getParent(), TheLoop, DT))
Loc.AATags.TBAA = nullptr;
- Accesses.addLoad(Loc, IsReadOnlyPtr);
+ // SCEV does not look through non-header PHIs inside the loop. Such phis can
+ // be analyzed by adding separate accesses for each incoming pointer value.
+ auto *PN = dyn_cast<PHINode>(Loc.Ptr);
+ if (PN && TheLoop->contains(PN->getParent()) &&
+ PN->getParent() != TheLoop->getHeader()) {
+ for (const Use &Inc : PN->incoming_values()) {
+ MemoryLocation NewLoc = Loc.getWithNewPtr(Inc);
+ Accesses.addLoad(NewLoc, IsReadOnlyPtr);
+ }
+ } else
+ Accesses.addLoad(Loc, IsReadOnlyPtr);
}
// If we write (or read-write) to a single destination and there are no
diff --git a/llvm/test/Analysis/LoopAccessAnalysis/pointer-phis.ll b/llvm/test/Analysis/LoopAccessAnalysis/pointer-phis.ll
index c803825896e96..dcdf6dd6a1fcb 100644
--- a/llvm/test/Analysis/LoopAccessAnalysis/pointer-phis.ll
+++ b/llvm/test/Analysis/LoopAccessAnalysis/pointer-phis.ll
@@ -6,7 +6,7 @@
define i32 @load_with_pointer_phi_no_runtime_checks(%s1* %data) {
; CHECK-LABEL: load_with_pointer_phi_no_runtime_checks
; CHECK-NEXT: loop.header:
-; CHECK-NEXT: Report: cannot identify array bounds
+; CHECK-NEXT: Memory dependences are safe
;
entry:
br label %loop.header
@@ -41,7 +41,7 @@ exit: ; preds = %loop.latch
define i32 @store_with_pointer_phi_no_runtime_checks(%s1* %data) {
; CHECK-LABEL: 'store_with_pointer_phi_no_runtime_checks'
; CHECK-NEXT: loop.header:
-; CHECK-NEXT: Report: cannot identify array bounds
+; CHECK-NEXT: Memory dependences are safe
;
entry:
br label %loop.header
@@ -76,7 +76,23 @@ exit: ; preds = %loop.latch
define i32 @store_with_pointer_phi_runtime_checks(double* %A, double* %B, double* %C) {
; CHECK-LABEL: 'store_with_pointer_phi_runtime_checks'
; CHECK-NEXT: loop.header:
-; CHECK-NEXT: Report: cannot identify array bounds
+; CHECK-NEXT: Memory dependences are safe with run-time checks
+; CHECK: Run-time memory checks:
+; CHECK-NEXT: Check 0:
+; CHECK-NEXT: Comparing group ([[GROUP_C:.+]]):
+; CHECK-NEXT: %gep.2 = getelementptr inbounds double, double* %C, i64 %iv
+; CHECK-NEXT: Against group ([[GROUP_B:.+]]):
+; CHECK-NEXT: %gep.1 = getelementptr inbounds double, double* %B, i64 %iv
+; CHECK-NEXT: Check 1:
+; CHECK-NEXT: Comparing group ([[GROUP_C]]):
+; CHECK-NEXT: %gep.2 = getelementptr inbounds double, double* %C, i64 %iv
+; CHECK-NEXT: Against group ([[GROUP_A:.+]]):
+; CHECK-NEXT: %arrayidx = getelementptr inbounds double, double* %A, i64 %iv
+; CHECK-NEXT: Check 2:
+; CHECK-NEXT: Comparing group ([[GROUP_B]]):
+; CHECK-NEXT: %gep.1 = getelementptr inbounds double, double* %B, i64 %iv
+; CHECK-NEXT: Against group ([[GROUP_A]]):
+; CHECK-NEXT: %arrayidx = getelementptr inbounds double, double* %A, i64 %iv
;
entry:
br label %loop.header
diff --git a/llvm/test/Transforms/LoopVectorize/vectorize-pointer-phis.ll b/llvm/test/Transforms/LoopVectorize/vectorize-pointer-phis.ll
index 53437e3d8c57d..e3168d5b5d350 100644
--- a/llvm/test/Transforms/LoopVectorize/vectorize-pointer-phis.ll
+++ b/llvm/test/Transforms/LoopVectorize/vectorize-pointer-phis.ll
@@ -4,7 +4,8 @@
define i32 @load_with_pointer_phi_no_runtime_checks(%s1* %data) {
; CHECK-LABEL: @load_with_pointer_phi_no_runtime_checks
-; CHECK-NOT: vector.body
+; CHECK-NOT: memcheck
+; CHECK: vector.body:
;
entry:
br label %loop.header
@@ -38,7 +39,8 @@ exit: ; preds = %loop.latch
define i32 @store_with_pointer_phi_no_runtime_checks(%s1* %data) {
; CHECK-LABEL: @store_with_pointer_phi_no_runtime_checks
-; CHECK-NOT: vector.body
+; CHECK-NOT: memcheck
+; CHECK: vector.body
;
entry:
br label %loop.header
@@ -72,7 +74,8 @@ exit: ; preds = %loop.latch
define i32 @store_with_pointer_phi_runtime_checks(double* %A, double* %B, double* %C) {
; CHECK-LABEL: @store_with_pointer_phi_runtime_checks
-; CHECK-NOT: vector.body
+; CHECK: memcheck
+; CHECK: vector.body
;
entry:
br label %loop.header
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