[llvm] r259861 - [LoopLoadElim] Don't allow versioning when optForSize
Adam Nemet via llvm-commits
llvm-commits at lists.llvm.org
Thu Feb 4 17:14:06 PST 2016
Author: anemet
Date: Thu Feb 4 19:14:05 2016
New Revision: 259861
URL: http://llvm.org/viewvc/llvm-project?rev=259861&view=rev
Log:
[LoopLoadElim] Don't allow versioning when optForSize
This was requested in the review of D16300.
Added:
llvm/trunk/test/Transforms/LoopLoadElim/opt-size.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopLoadElimination.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LoopLoadElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopLoadElimination.cpp?rev=259861&r1=259860&r2=259861&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopLoadElimination.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopLoadElimination.cpp Thu Feb 4 19:14:05 2016
@@ -465,9 +465,16 @@ public:
return false;
}
- // Point of no-return, start the transformation. First, version the loop if
- // necessary.
if (!Checks.empty() || !LAI.PSE.getUnionPredicate().isAlwaysTrue()) {
+ if (L->getHeader()->getParent()->optForSize()) {
+ DEBUG(dbgs() << "Versioning is needed but not allowed when optimizing "
+ "for size.\n");
+ return false;
+ }
+
+ // Point of no-return, start the transformation. First, version the loop
+ // if necessary.
+
LoopVersioning LV(LAI, L, LI, DT, PSE.getSE(), false);
LV.setAliasChecks(std::move(Checks));
LV.setSCEVChecks(LAI.PSE.getUnionPredicate());
Added: llvm/trunk/test/Transforms/LoopLoadElim/opt-size.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopLoadElim/opt-size.ll?rev=259861&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopLoadElim/opt-size.ll (added)
+++ llvm/trunk/test/Transforms/LoopLoadElim/opt-size.ll Thu Feb 4 19:14:05 2016
@@ -0,0 +1,76 @@
+; RUN: opt -basicaa -loop-load-elim -S < %s | FileCheck %s
+
+; When optimizing for size don't eliminate in this loop because the loop would
+; have to be versioned first because A and C may alias.
+;
+; for (unsigned i = 0; i < 100; i++) {
+; A[i+1] = B[i] + 2;
+; C[i] = A[i] * 2;
+; }
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+; CHECK-LABEL: @f(
+define void @f(i32* %A, i32* %B, i32* %C, i64 %N) optsize {
+
+entry:
+ br label %for.body
+
+for.body: ; preds = %for.body, %entry
+ %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+
+ %Aidx_next = getelementptr inbounds i32, i32* %A, i64 %indvars.iv.next
+ %Bidx = getelementptr inbounds i32, i32* %B, i64 %indvars.iv
+ %Cidx = getelementptr inbounds i32, i32* %C, i64 %indvars.iv
+ %Aidx = getelementptr inbounds i32, i32* %A, i64 %indvars.iv
+
+ %b = load i32, i32* %Bidx, align 4
+ %a_p1 = add i32 %b, 2
+ store i32 %a_p1, i32* %Aidx_next, align 4
+
+ %a = load i32, i32* %Aidx, align 4
+; CHECK: %c = mul i32 %a, 2
+ %c = mul i32 %a, 2
+ store i32 %c, i32* %Cidx, align 4
+
+ %exitcond = icmp eq i64 %indvars.iv.next, %N
+ br i1 %exitcond, label %for.end, label %for.body
+
+for.end: ; preds = %for.body
+ ret void
+}
+
+; Same loop but with noalias on %A and %C. In this case load-eliminate even
+; with -Os.
+
+; CHECK-LABEL: @g(
+define void @g(i32* noalias %A, i32* %B, i32* noalias %C, i64 %N) optsize {
+
+entry:
+ br label %for.body
+
+for.body: ; preds = %for.body, %entry
+ %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+
+ %Aidx_next = getelementptr inbounds i32, i32* %A, i64 %indvars.iv.next
+ %Bidx = getelementptr inbounds i32, i32* %B, i64 %indvars.iv
+ %Cidx = getelementptr inbounds i32, i32* %C, i64 %indvars.iv
+ %Aidx = getelementptr inbounds i32, i32* %A, i64 %indvars.iv
+
+ %b = load i32, i32* %Bidx, align 4
+ %a_p1 = add i32 %b, 2
+ store i32 %a_p1, i32* %Aidx_next, align 4
+
+ %a = load i32, i32* %Aidx, align 4
+; CHECK: %c = mul i32 %store_forwarded, 2
+ %c = mul i32 %a, 2
+ store i32 %c, i32* %Cidx, align 4
+
+ %exitcond = icmp eq i64 %indvars.iv.next, %N
+ br i1 %exitcond, label %for.end, label %for.body
+
+for.end: ; preds = %for.body
+ ret void
+}
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