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Teach LoopUnrollPass to respect loop unrolling hints in metadata.
See http://reviews.llvm.org/D4090 for more details. The Clang change that produces this metadata was committed in r210667 Patch by Mark Heffernan. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210721 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Bendersky
parent
02503401b4
commit
87fcb536ab
@ -20,6 +20,7 @@
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Metadata.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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@ -36,7 +37,8 @@ UnrollThreshold("unroll-threshold", cl::init(150), cl::Hidden,
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static cl::opt<unsigned>
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UnrollCount("unroll-count", cl::init(0), cl::Hidden,
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cl::desc("Use this unroll count for all loops, for testing purposes"));
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cl::desc("Use this unroll count for all loops including those with "
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"unroll_count pragma values, for testing purposes"));
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static cl::opt<bool>
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UnrollAllowPartial("unroll-allow-partial", cl::init(false), cl::Hidden,
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@ -47,6 +49,13 @@ static cl::opt<bool>
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UnrollRuntime("unroll-runtime", cl::ZeroOrMore, cl::init(false), cl::Hidden,
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cl::desc("Unroll loops with run-time trip counts"));
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// Maximum allowed unroll count for a loop being fully unrolled
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// because of a pragma unroll(enable) statement (ie, metadata
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// "llvm.loopunroll.enable" is true). This prevents unexpected
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// behavior like crashing when using this pragma on high trip count
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// loops.
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static const unsigned PragmaFullUnrollCountLimit = 1024;
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namespace {
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class LoopUnroll : public LoopPass {
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public:
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@ -151,6 +160,63 @@ static unsigned ApproximateLoopSize(const Loop *L, unsigned &NumCalls,
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return LoopSize;
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}
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// Returns the value associated with the given metadata node name (for
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// example, "llvm.loopunroll.count"). If no such named metadata node
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// exists, then nullptr is returned.
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static const ConstantInt *GetUnrollMetadataValue(const Loop *L,
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StringRef Name) {
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MDNode *LoopID = L->getLoopID();
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if (!LoopID) return nullptr;
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// First operand should refer to the loop id itself.
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assert(LoopID->getNumOperands() > 0 && "requires at least one operand");
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assert(LoopID->getOperand(0) == LoopID && "invalid loop id");
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for (unsigned i = 1, e = LoopID->getNumOperands(); i < e; ++i) {
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const MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
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if (!MD) continue;
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const MDString *S = dyn_cast<MDString>(MD->getOperand(0));
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if (!S) continue;
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if (Name.equals(S->getString())) {
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assert(MD->getNumOperands() == 2 &&
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"Unroll hint metadata should have two operands.");
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return cast<ConstantInt>(MD->getOperand(1));
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}
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}
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return nullptr;
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}
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// Returns true if the loop has an unroll(enable) pragma.
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static bool HasUnrollEnablePragma(const Loop *L) {
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const ConstantInt *EnableValue =
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GetUnrollMetadataValue(L, "llvm.loopunroll.enable");
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return (EnableValue && EnableValue->getZExtValue());
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return false;
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}
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// Returns true if the loop has an unroll(disable) pragma.
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static bool HasUnrollDisablePragma(const Loop *L) {
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const ConstantInt *EnableValue =
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GetUnrollMetadataValue(L, "llvm.loopunroll.enable");
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return (EnableValue && !EnableValue->getZExtValue());
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return false;
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}
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// Check for unroll_count(N) pragma. If found, return true and set
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// Count to the integer parameter of the pragma.
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static bool HasUnrollCountPragma(const Loop *L, int &Count) {
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const ConstantInt *CountValue =
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GetUnrollMetadataValue(L, "llvm.loopunroll.count");
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if (CountValue) {
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Count = CountValue->getZExtValue();
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assert(Count >= 1 && "Unroll count must be positive.");
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return true;
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}
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return false;
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}
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bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
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if (skipOptnoneFunction(L))
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return false;
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@ -202,12 +268,49 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
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TripMultiple = SE->getSmallConstantTripMultiple(L, LatchBlock);
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}
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bool Runtime = UserRuntime ? CurrentRuntime : UP.Runtime;
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// User-specified count (either as a command-line option or
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// constructor parameter) has highest precedence.
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unsigned Count = UserCount ? CurrentCount : 0;
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// Use a default unroll-count if the user doesn't specify a value
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// and the trip count is a run-time value. The default is different
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// for run-time or compile-time trip count loops.
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unsigned Count = UserCount ? CurrentCount : UP.Count;
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// If there is no user-specified count, unroll pragmas have the next
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// highest precendence.
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if (Count == 0) {
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if (HasUnrollDisablePragma(L)) {
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// Loop has unroll(disable) pragma.
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return false;
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}
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int PragmaCount;
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if (HasUnrollCountPragma(L, PragmaCount)) {
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if (PragmaCount == 1) {
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// Nothing to do.
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return false;
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}
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Count = PragmaCount;
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Threshold = NoThreshold;
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} else if (HasUnrollEnablePragma(L)) {
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// Loop has unroll(enable) pragma without a unroll_count pragma,
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// so unroll loop fully if possible.
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if (TripCount == 0) {
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DEBUG(dbgs() << " Loop has unroll(enable) pragma but loop cannot be "
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"fully unrolled because trip count is unknown.\n");
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// Continue with standard heuristic unrolling.
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} else if (TripCount > PragmaFullUnrollCountLimit) {
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DEBUG(dbgs() << " Loop has unroll(enable) pragma but loop cannot be "
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"fully unrolled because loop count is greater than "
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<< PragmaFullUnrollCountLimit);
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// Continue with standard heuristic unrolling.
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} else {
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Count = TripCount;
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Threshold = NoThreshold;
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}
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}
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}
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if (Count == 0)
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Count = UP.Count;
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bool Runtime = UserRuntime ? CurrentRuntime : UP.Runtime;
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if (Runtime && Count == 0 && TripCount == 0)
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Count = UnrollRuntimeCount;
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285
test/Transforms/LoopUnroll/unroll-pragmas.ll
Normal file
285
test/Transforms/LoopUnroll/unroll-pragmas.ll
Normal file
@ -0,0 +1,285 @@
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; RUN: opt < %s -loop-unroll -S | FileCheck %s
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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; loop4 contains a small loop which should be completely unrolled by
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; the default unrolling heuristics. It serves as a control for the
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; unroll(disable) pragma test loop4_with_disable.
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;
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; CHECK-LABEL: @loop4(
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; CHECK-NOT: br i1
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define void @loop4(i32* nocapture %a) {
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entry:
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
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%arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
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%0 = load i32* %arrayidx, align 4
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%inc = add nsw i32 %0, 1
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store i32 %inc, i32* %arrayidx, align 4
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%exitcond = icmp eq i64 %indvars.iv.next, 4
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br i1 %exitcond, label %for.end, label %for.body
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for.end: ; preds = %for.body
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ret void
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}
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; #pragma clang loop unroll(disable)
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;
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; CHECK-LABEL: @loop4_with_disable(
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; CHECK: store i32
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; CHECK-NOT: store i32
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; CHECK: br i1
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define void @loop4_with_disable(i32* nocapture %a) {
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entry:
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
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%arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
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%0 = load i32* %arrayidx, align 4
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%inc = add nsw i32 %0, 1
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store i32 %inc, i32* %arrayidx, align 4
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%exitcond = icmp eq i64 %indvars.iv.next, 4
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br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !1
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for.end: ; preds = %for.body
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ret void
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}
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!1 = metadata !{metadata !1, metadata !2}
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!2 = metadata !{metadata !"llvm.loopunroll.enable", i1 false}
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; loop64 has a high enough count that it should *not* be unrolled by
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; the default unrolling heuristic. It serves as the control for the
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; unroll(enable) pragma test loop64_with_.* tests below.
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;
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; CHECK-LABEL: @loop64(
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; CHECK: store i32
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; CHECK-NOT: store i32
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; CHECK: br i1
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define void @loop64(i32* nocapture %a) {
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entry:
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
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%arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
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%0 = load i32* %arrayidx, align 4
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%inc = add nsw i32 %0, 1
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store i32 %inc, i32* %arrayidx, align 4
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%exitcond = icmp eq i64 %indvars.iv.next, 64
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br i1 %exitcond, label %for.end, label %for.body
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for.end: ; preds = %for.body
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ret void
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}
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; #pragma clang loop unroll(enable)
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; Loop should be fully unrolled.
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;
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; CHECK-LABEL: @loop64_with_enable(
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; CHECK-NOT: br i1
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define void @loop64_with_enable(i32* nocapture %a) {
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entry:
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
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%arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
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%0 = load i32* %arrayidx, align 4
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%inc = add nsw i32 %0, 1
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store i32 %inc, i32* %arrayidx, align 4
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%exitcond = icmp eq i64 %indvars.iv.next, 64
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br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !3
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for.end: ; preds = %for.body
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ret void
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}
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!3 = metadata !{metadata !3, metadata !4}
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!4 = metadata !{metadata !"llvm.loopunroll.enable", i1 true}
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; #pragma clang loop unroll_count(4)
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; Loop should be unrolled 4 times.
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;
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; CHECK-LABEL: @loop64_with_count4(
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; CHECK: store i32
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; CHECK: store i32
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; CHECK: store i32
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; CHECK: store i32
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; CHECK-NOT: store i32
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; CHECK: br i1
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define void @loop64_with_count4(i32* nocapture %a) {
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entry:
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
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%arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
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%0 = load i32* %arrayidx, align 4
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%inc = add nsw i32 %0, 1
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store i32 %inc, i32* %arrayidx, align 4
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%exitcond = icmp eq i64 %indvars.iv.next, 64
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br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !5
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for.end: ; preds = %for.body
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ret void
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}
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!5 = metadata !{metadata !5, metadata !6}
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!6 = metadata !{metadata !"llvm.loopunroll.count", i32 4}
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; #pragma clang loop unroll_count(enable) unroll_count(4)
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; Loop should be unrolled 4 times.
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;
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; CHECK-LABEL: @loop64_with_enable_and_count4(
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; CHECK: store i32
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; CHECK: store i32
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; CHECK: store i32
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; CHECK: store i32
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; CHECK-NOT: store i32
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; CHECK: br i1
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define void @loop64_with_enable_and_count4(i32* nocapture %a) {
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entry:
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
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%arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
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%0 = load i32* %arrayidx, align 4
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%inc = add nsw i32 %0, 1
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store i32 %inc, i32* %arrayidx, align 4
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%exitcond = icmp eq i64 %indvars.iv.next, 64
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br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !7
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for.end: ; preds = %for.body
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ret void
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}
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!7 = metadata !{metadata !7, metadata !6, metadata !4}
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; #pragma clang loop unroll_count(enable)
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; Full unrolling is requested, but loop has a dynamic trip count so
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; no unrolling should occur.
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;
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; CHECK-LABEL: @dynamic_loop_with_enable(
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; CHECK: store i32
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; CHECK-NOT: store i32
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; CHECK: br i1
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define void @dynamic_loop_with_enable(i32* nocapture %a, i32 %b) {
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entry:
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%cmp3 = icmp sgt i32 %b, 0
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br i1 %cmp3, label %for.body, label %for.end, !llvm.loop !8
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for.body: ; preds = %entry, %for.body
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%indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
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%arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
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%0 = load i32* %arrayidx, align 4
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%inc = add nsw i32 %0, 1
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store i32 %inc, i32* %arrayidx, align 4
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%lftr.wideiv = trunc i64 %indvars.iv.next to i32
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%exitcond = icmp eq i32 %lftr.wideiv, %b
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br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !8
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for.end: ; preds = %for.body, %entry
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ret void
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}
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!8 = metadata !{metadata !8, metadata !4}
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; #pragma clang loop unroll_count(4)
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; Loop has a dynamic trip count. Unrolling should occur, but no
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; conditional branches can be removed.
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;
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; CHECK-LABEL: @dynamic_loop_with_count4(
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; CHECK-NOT: store
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; CHECK: br i1
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; CHECK: store
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; CHECK: br i1
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; CHECK: store
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; CHECK: br i1
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; CHECK: store
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; CHECK: br i1
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; CHECK: store
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; CHECK: br i1
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; CHECK-NOT: br i1
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define void @dynamic_loop_with_count4(i32* nocapture %a, i32 %b) {
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entry:
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%cmp3 = icmp sgt i32 %b, 0
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br i1 %cmp3, label %for.body, label %for.end, !llvm.loop !9
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for.body: ; preds = %entry, %for.body
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%indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
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%arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
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%0 = load i32* %arrayidx, align 4
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%inc = add nsw i32 %0, 1
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store i32 %inc, i32* %arrayidx, align 4
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%lftr.wideiv = trunc i64 %indvars.iv.next to i32
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%exitcond = icmp eq i32 %lftr.wideiv, %b
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br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !9
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for.end: ; preds = %for.body, %entry
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ret void
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}
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!9 = metadata !{metadata !9, metadata !6}
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; #pragma clang loop unroll_count(1)
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; Loop should not be unrolled
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;
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; CHECK-LABEL: @unroll_1(
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; CHECK: store i32
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; CHECK-NOT: store i32
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; CHECK: br i1
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define void @unroll_1(i32* nocapture %a, i32 %b) {
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entry:
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
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%arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
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%0 = load i32* %arrayidx, align 4
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%inc = add nsw i32 %0, 1
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store i32 %inc, i32* %arrayidx, align 4
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%exitcond = icmp eq i64 %indvars.iv.next, 4
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br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !10
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for.end: ; preds = %for.body
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ret void
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}
|
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!10 = metadata !{metadata !10, metadata !11}
|
||||
!11 = metadata !{metadata !"llvm.loopunroll.count", i32 1}
|
||||
|
||||
; #pragma clang loop unroll(enable)
|
||||
; Loop has very high loop count (1 million) and full unrolling was requested.
|
||||
; Loop should not be unrolled.
|
||||
;
|
||||
; CHECK-LABEL: @unroll_1M(
|
||||
; CHECK: store i32
|
||||
; CHECK-NOT: store i32
|
||||
; CHECK: br i1
|
||||
define void @unroll_1M(i32* nocapture %a, i32 %b) {
|
||||
entry:
|
||||
br label %for.body
|
||||
|
||||
for.body: ; preds = %for.body, %entry
|
||||
%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
|
||||
%arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
|
||||
%0 = load i32* %arrayidx, align 4
|
||||
%inc = add nsw i32 %0, 1
|
||||
store i32 %inc, i32* %arrayidx, align 4
|
||||
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
|
||||
%exitcond = icmp eq i64 %indvars.iv.next, 1000000
|
||||
br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !12
|
||||
|
||||
for.end: ; preds = %for.body
|
||||
ret void
|
||||
}
|
||||
!12 = metadata !{metadata !12, metadata !4}
|
||||
Loading…
Reference in New Issue
Block a user