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[Unroll] Fix a bug in UnrolledInstAnalyzer::visitLoad. 

We only checked that a global is initialized with constants, which is
incorrect. We should be checking that GlobalVariable *is* a constant,
not just initialized with it.

llvm-svn: 247769
This commit is contained in:
Michael Zolotukhin 2015-09-16 03:25:09 +00:00
parent 141dd91ac5
commit fc314be0ec
2 changed files with 30 additions and 1 deletions
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2
llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
View File

@ -415,7 +415,7 @@ private:
auto *GV = dyn_cast<GlobalVariable>(AddressIt->second.Base);
// We're only interested in loads that can be completely folded to a
// constant.
if (!GV || !GV->hasInitializer())
if (!GV || !GV->hasInitializer() || !GV->isConstant())
return false;
ConstantDataSequential *CDS =

29
llvm/test/Transforms/LoopUnroll/full-unroll-heuristics-2.ll Normal file
View File

@ -0,0 +1,29 @@
; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-threshold=10 -unroll-percent-dynamic-cost-saved-threshold=50 -unroll-dynamic-cost-savings-discount=90 | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
; Though @unknown_global is initialized with constant values, we can't consider
; it as a constant, so we shouldn't unroll the loop.
; CHECK: %array_const_idx = getelementptr inbounds [9 x i32], [9 x i32]* @unknown_global, i64 0, i64 %iv
@unknown_global = internal unnamed_addr global [9 x i32] [i32 0, i32 -1, i32 0, i32 -1, i32 5, i32 -1, i32 0, i32 -1, i32 0], align 16
define i32 @foo(i32* noalias nocapture readonly %src) {
entry:
br label %loop
loop: ; preds = %loop, %entry
%iv = phi i64 [ 0, %entry ], [ %inc, %loop ]
%r = phi i32 [ 0, %entry ], [ %add, %loop ]
%arrayidx = getelementptr inbounds i32, i32* %src, i64 %iv
%src_element = load i32, i32* %arrayidx, align 4
%array_const_idx = getelementptr inbounds [9 x i32], [9 x i32]* @unknown_global, i64 0, i64 %iv
%const_array_element = load i32, i32* %array_const_idx, align 4
%mul = mul nsw i32 %src_element, %const_array_element
%add = add nsw i32 %mul, %r
%inc = add nuw nsw i64 %iv, 1
%exitcond86.i = icmp eq i64 %inc, 9
br i1 %exitcond86.i, label %loop.end, label %loop
loop.end: ; preds = %loop
%r.lcssa = phi i32 [ %r, %loop ]
ret i32 %r.lcssa
}