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[LoopLoadElim] Don't allow versioning when optForSize

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This was requested in the review of D16300.

llvm-svn: 259861
This commit is contained in:
Adam Nemet 2016-02-05 01:14:05 +00:00
parent 80e3178c23
commit f087442a31
2 changed files with 85 additions and 2 deletions
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11
lib/Transforms/Scalar/LoopLoadElimination.cpp
View File

@ -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());

76
test/Transforms/LoopLoadElim/opt-size.ll Normal file
View File

@ -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
}